Effortlessly calculate the molar mass of chemical compounds.
Chemical Formula Weight Calculator
Enter the chemical formula (e.g., H2O, NaCl). Use standard notation for elements and numbers for subscripts. For hydrates, use a dot, e.g., CuSO4.5H2O.
Provide atomic masses for elements not found in standard tables or for custom precision. Format: ElementSymbol: Mass, ElementSymbol: Mass
Calculation Results
—
Formula Weight: — g/mol
Total Atoms: —
Element Breakdown: —
Formula Used: Sum of (Number of atoms of element * Atomic mass of element) for all elements in the compound.
Atomic Mass Contribution Chart
Element Atomic Mass Table
Element
Atomic Mass (g/mol)
Count in Formula
Contribution (g/mol)
What is Formula Weight (Molar Mass) in Chemistry?
Formula weight, often used interchangeably with molar mass, is a fundamental concept in chemistry. It represents the sum of the atomic weights of all atoms in a chemical formula. For ionic compounds, which exist as extended lattices rather than discrete molecules, "formula weight" is the technically more accurate term, though "molar mass" is widely accepted. This value is crucial for stoichiometric calculations, determining concentrations, and understanding the mass relationships in chemical reactions. It tells you the mass of one mole of a substance, where a mole is a specific number of particles (Avogadro's number, approximately 6.022 x 10^23).
Who should use it: Anyone studying or working with chemistry, including students, researchers, chemists, pharmacists, material scientists, and chemical engineers, will frequently use formula weight. It's essential for laboratory work, theoretical calculations, and understanding chemical compositions.
Common misconceptions: A common misconception is confusing atomic mass with atomic weight, or assuming that molecular weight and formula weight are always identical. While closely related, atomic mass is the mass of a single atom, and atomic weight is the average atomic mass of an element considering its isotopes. Molecular weight applies specifically to covalent compounds (molecules), whereas formula weight is a broader term applicable to all chemical compounds, including ionic ones. Another misconception is that the formula weight is simply the sum of the atomic numbers; this is incorrect as it ignores isotopes and the actual masses of atoms.
Formula Weight Calculator Chemistry Formula and Mathematical Explanation
The calculation of formula weight is straightforward but requires careful attention to the chemical formula. It involves identifying each element present, counting the number of atoms of each element, and using their respective atomic masses.
Step-by-Step Derivation
Identify Elements: Examine the chemical formula to list all unique elements present.
Count Atoms: For each element, determine the number of atoms. This is indicated by the subscript following the element symbol. If no subscript is present, assume one atom. For complex formulas with parentheses (e.g., Ca(OH)2), multiply the subscript outside the parenthesis by the subscript inside for each element within.
Find Atomic Masses: Obtain the atomic mass (usually listed as atomic weight) for each element from the periodic table. These are typically given in atomic mass units (amu), but for molar mass calculations, we use the equivalent value in grams per mole (g/mol).
Calculate Contribution: For each element, multiply the number of atoms by its atomic mass. This gives the total mass contribution of that element to the compound's formula weight.
Sum Contributions: Add up the contributions from all elements to find the total formula weight of the compound.
Variables and Explanations
Chemical Formula: A symbolic representation of a chemical substance, showing the types of atoms and the number of each type in one molecule or formula unit.
Element Symbol: A one- or two-letter abbreviation for a chemical element (e.g., H for Hydrogen, O for Oxygen, Na for Sodium).
Atomic Mass (or Atomic Weight): The average mass of atoms of an element, calculated using the relative abundance of isotopes. Expressed in g/mol for molar mass calculations.
Atom Count: The number of atoms of a specific element within one molecule or formula unit, as indicated by subscripts in the chemical formula.
Formula Weight (Molar Mass): The sum of the atomic masses of all atoms in a chemical formula. Units: grams per mole (g/mol).
Variable Table
Variable
Meaning
Unit
Typical Range
Element Symbol
Abbreviation for a chemical element
N/A
See periodic table
Atomic Mass
Average mass of an element's atoms
g/mol
~0.1 (H) to ~200+ (e.g., U)
Atom Count
Number of atoms of an element in the formula
Unitless
1 or more
Formula Weight
Total mass of one mole of the compound
g/mol
Depends on compound; > ~18 (H2O)
Practical Examples (Real-World Use Cases)
Example 1: Water (H₂O)
Inputs:
Chemical Formula: H2O
Calculation Steps:
Elements: Hydrogen (H), Oxygen (O)
Atom Counts: H = 2, O = 1
Atomic Masses (approx.): H = 1.008 g/mol, O = 15.999 g/mol
Contributions: H = 2 * 1.008 = 2.016 g/mol; O = 1 * 15.999 = 15.999 g/mol
Sum: 2.016 + 15.999 = 18.015 g/mol
Outputs:
Formula Weight: 18.015 g/mol
Total Atoms: 3
Element Breakdown: H: 2, O: 1
Interpretation: This means that one mole of water molecules has a mass of approximately 18.015 grams. This is fundamental for calculating the amount of reactants or products in reactions involving water.
Example 2: Copper(II) Sulfate Pentahydrate (CuSO₄·5H₂O)
Interpretation: One mole of copper(II) sulfate pentahydrate crystals weighs approximately 259.677 grams. This is vital for solution preparation or synthesis reactions involving this common laboratory chemical.
How to Use This Formula Weight Calculator
Our free online formula weight calculator chemistry tool is designed for ease of use and accuracy. Follow these simple steps:
Enter the Chemical Formula: In the "Chemical Formula" field, type the exact chemical formula of the substance you want to analyze. Ensure correct capitalization for element symbols and use numbers for subscripts (e.g., H2O, C6H12O6). For hydrates, use a period to separate the anhydrous salt from the water molecules (e.g., MgSO4.7H2O).
Optional: Provide Custom Atomic Masses: If you need to use highly specific atomic masses or masses for elements not commonly found, you can enter them in the "Element Atomic Masses" text area. Format each entry as "ElementSymbol: Mass" separated by commas (e.g., "H: 1.0079, O: 15.9994"). If left blank, the calculator will use standard atomic masses from its internal database.
Click Calculate: Press the "Calculate" button.
How to Read Results:
Main Highlighted Result: This prominently displays the calculated Formula Weight in g/mol.
Intermediate Values: You'll see the total count of atoms in the formula and a breakdown of how many atoms of each element contribute to the total weight.
Formula Explanation: A clear statement of the calculation method used.
Atomic Mass Contribution Chart: A visual representation showing the proportion each element's mass contributes to the total formula weight.
Element Atomic Mass Table: A detailed table breaking down the calculation per element, showing its atomic mass, count, and its specific contribution to the total formula weight.
Decision-Making Guidance:
The formula weight is essential for many chemical decisions. For example, if you need to prepare a 0.1 M solution of NaCl (sodium chloride), you first calculate its formula weight (approx. 58.44 g/mol). Then, you'd know that dissolving 58.44 grams of NaCl in water to make a final solution volume of 1 liter yields a 1 M solution. For a 0.1 M solution, you'd dissolve 5.844 grams.
Key Factors That Affect Formula Weight Calculations
While the core calculation is consistent, several factors can influence the perceived or precise value of formula weight in practical applications:
Isotopic Abundance: Standard atomic weights are averages based on the natural abundance of an element's isotopes. If you are working with specific isotopes (e.g., in nuclear chemistry or advanced mass spectrometry), you would use the exact isotopic mass, not the standard atomic weight.
Purity of Sample: The calculated formula weight assumes a pure compound. Impurities will alter the actual measured mass of a given molar quantity. For accurate work, sample purity is critical.
Hydration State: As seen in the CuSO₄·5H₂O example, water molecules incorporated into a crystal lattice (hydrates) significantly increase the formula weight. It's crucial to specify whether a compound is anhydrous or hydrated.
Precision of Atomic Masses: Different periodic tables or databases may provide atomic masses to varying degrees of precision. For high-accuracy calculations, using more precise values is necessary. Our calculator defaults to standard, precise values.
Significant Figures: The result should be reported with an appropriate number of significant figures, usually dictated by the least precise atomic mass used in the calculation.
Temperature and Pressure (for Gases): While formula weight itself is independent of temperature and pressure, the molar volume of gaseous substances is highly dependent on these conditions. This affects calculations involving gas densities or volumes derived from mass.
Radioactive Decay: For radioactive elements, their atomic masses can change over time due to decay, although this is usually relevant only over very long timescales or in specific nuclear contexts.
Frequently Asked Questions (FAQ)
What is the difference between atomic weight, molecular weight, and formula weight?
Atomic weight is the average mass of atoms of an element. Molecular weight is the sum of atomic weights for atoms in a molecule (covalent compounds). Formula weight is a more general term, the sum of atomic weights for atoms in a chemical formula unit, applicable to all compounds, including ionic ones.
Can I calculate the formula weight for ions?
Yes, you can calculate the formula weight for an ion by summing the atomic masses of the constituent atoms, just as you would for a neutral compound. For example, the formula weight of the sulfate ion (SO₄²⁻) is calculated similarly to sulfur dioxide (SO₂) but includes 4 oxygen atoms.
How accurate are the results from this calculator?
The accuracy depends on the standard atomic masses used. This calculator uses widely accepted atomic mass values from the IUPAC. For specialized applications requiring isotopic masses, you may need to input custom values.
What does g/mol mean?
g/mol stands for grams per mole. It is the unit for molar mass, indicating the mass in grams of one mole (approximately 6.022 x 10^23 particles) of a substance.
How do I handle parentheses in chemical formulas, like Ca(OH)₂?
When you encounter parentheses, multiply the count of each atom inside the parentheses by the subscript outside the parentheses. For Ca(OH)₂, you have 1 Calcium (Ca), 1 Oxygen (O) * 2 = 2 Oxygen atoms, and 1 Hydrogen (H) * 2 = 2 Hydrogen atoms.
What if an element is not in the standard periodic table?
This calculator uses standard atomic masses. If you're working with a theoretical element or an isotope with a known mass not listed, use the optional "Element Atomic Masses" input field to provide its specific mass.
Why is formula weight important for reactions?
It's essential for stoichiometry – the quantitative relationship between reactants and products. Knowing the formula weight allows chemists to convert between mass and moles, which is necessary to accurately measure reactants and predict product yields.
Can this calculator handle complex organic molecules?
Yes, as long as the chemical formula is provided in a standard format (e.g., C6H12O6 for glucose), the calculator can determine the formula weight. For very large biomolecules, manual input might become cumbersome.
Related Tools and Internal Resources
Molarity Calculator: Use formula weight to easily calculate solution concentrations.
// Standard atomic masses (g/mol) – sourced from IUPAC
var atomicMasses = {
"H": 1.008, "He": 4.0026, "Li": 6.94, "Be": 9.0122, "B": 10.81, "C": 12.011, "N": 14.007, "O": 15.999, "F": 18.998, "Ne": 20.180,
"Na": 22.990, "Mg": 24.305, "Al": 26.982, "Si": 28.085, "P": 30.974, "S": 32.06, "Cl": 35.45, "Ar": 39.948, "K": 39.098, "Ca": 40.078,
"Sc": 44.956, "Ti": 47.867, "V": 50.942, "Cr": 51.996, "Mn": 54.938, "Fe": 55.845, "Co": 58.933, "Ni": 58.693, "Cu": 63.546, "Zn": 65.38,
"Ga": 69.723, "Ge": 72.630, "As": 74.922, "Se": 78.971, "Br": 79.904, "Kr": 83.798, "Rb": 85.468, "Sr": 87.62, "Y": 88.906, "Zr": 91.224,
"Nb": 92.906, "Mo": 95.95, "Tc": 98.0, "Ru": 101.07, "Rh": 102.91, "Pd": 106.42, "Ag": 107.87, "Cd": 112.41, "In": 114.82, "Sn": 118.71,
"Sb": 121.76, "Te": 127.60, "I": 126.90, "Xe": 131.29, "Cs": 132.91, "Ba": 137.33, "La": 138.91, "Ce": 140.12, "Pr": 140.91, "Nd": 144.24,
"Pm": 145.0, "Sm": 150.36, "Eu": 151.96, "Gd": 157.25, "Tb": 158.93, "Dy": 162.50, "Ho": 164.93, "Er": 167.26, "Tm": 168.93, "Yb": 173.05,
"Lu": 174.97, "Hf": 178.49, "Ta": 180.95, "W": 183.84, "Re": 186.21, "Os": 190.23, "Ir": 192.22, "Pt": 195.08, "Au": 196.97, "Hg": 200.59,
"Tl": 204.38, "Pb": 207.2, "Bi": 208.98, "Po": 209.0, "At": 210.0, "Rn": 222.0, "Fr": 223.0, "Ra": 226.0, "Ac": 227.0, "Th": 232.04,
"Pa": 231.04, "U": 238.03
};
var elementsInFormula = {};
var totalAtomCount = 0;
var formulaWeightResult = 0;
var chartData = [];
var chartInstance = null;
function parseChemicalFormula(formula) {
elementsInFormula = {};
totalAtomCount = 0;
var regex = /([A-Z][a-z]*)(\d*)|(\.)(\d*)/g;
var match;
var currentMultiplier = 1;
var hydratePart = false;
// Handle optional custom masses first
var customMassesInput = document.getElementById('elementMasses').value.trim();
var customMasses = {};
if (customMassesInput) {
var pairs = customMassesInput.split(',');
for (var i = 0; i 0) {
customMasses[symbol] = mass;
} else {
throw new Error("Invalid custom atomic mass for " + symbol);
}
} else {
throw new Error("Invalid format for custom atomic masses. Use 'Symbol: Mass'.");
}
}
}
// Process the formula string
formula = formula.replace(/\s+/g, "); // Remove whitespace
var processedFormula = formula.replace(/\. *(\d*)/g, '.$1'); // Normalize hydrate notation
// Regex to find elements and their counts, or hydrate multipliers
// Handles cases like H2O, C6H12O6, SO4, Ca(OH)2, CuSO4.5H2O
regex = /([A-Z][a-z]*)(\d*)|(\()|(\))(\d*)|(\.)(\d*)/g;
var parts = [];
var lastIndex = 0;
while ((match = regex.exec(processedFormula)) !== null) {
if (match.index > lastIndex) {
// This handles any characters between matches, which should ideally not happen in a valid formula
// Or it could capture parts not covered by the regex like the dot for hydrates
if (processedFormula.substring(lastIndex, match.index).trim()) {
console.warn("Unexpected characters found:", processedFormula.substring(lastIndex, match.index));
}
}
parts.push(match);
lastIndex = regex.lastIndex;
}
if (lastIndex < processedFormula.length) {
console.warn("Unprocessed end of formula:", processedFormula.substring(lastIndex));
}
var elementCounts = {};
var multipliers = [1]; // Stack for nested parentheses
for (var i = 0; i 1) {
multipliers.pop();
} else {
// Error: Unmatched closing parenthesis
throw new Error("Mismatched parentheses in formula.");
}
} else if (dot) {
var dotMultiplier = dotCountStr ? parseInt(dotCountStr) : 1;
if (isNaN(dotMultiplier)) dotMultiplier = 1;
// This dot signifies hydration, apply multiplier to subsequent elements.
// A more robust parser would handle this better, but for common cases:
// Assume dot is followed by H2O or similar, needs careful parsing.
// A simple approach: if a number follows the dot, it's the multiplier for subsequent water.
// This is simplified: it assumes the dot format is X.YH2O where Y is dotCountStr.
// For simplicity, we will handle standard hydrate notation like CuSO4.5H2O
// by appending the H2O counts directly.
// Let's refine: if we see ".number", we add the count of water molecules
// and their atoms. This requires a lookahead or post-processing.
// A simpler approach: treat '.5H2O' as a separate group that adds atoms.
// The regex needs to be smarter or we need post-processing.
// Let's try to parse the hydrate part separately if it exists.
// If we see a dot, assume it's a hydrate. We'll re-parse after the dot.
// This requires a simpler loop and potentially recursion or more complex state.
// Let's refine the regex for simplicity and handle hydrates separately if needed.
// Basic approach:
// Iterate through formula:
// If element + optional number: add to counts
// If '(': push multiplier, update current multiplier
// If ')': pop multiplier
// If '.': treat the rest as a sub-formula to be multiplied.
// Re-thinking parsing logic for hydrates like CuSO4.5H2O
// Split by '.'
// Parse first part (CuSO4)
// Parse second part (5H2O)
// Add counts from second part multiplied by the number before H2O
// This current regex logic might struggle with complex hydrates directly.
// Let's stick to parsing elements and counts first.
// The dot logic needs careful handling – let's assume it's followed by number and H2O for now.
// The initial regex approach is better for element-count pairs.
// Let's refine the initial regex to capture element-count or standalone elements.
// New regex attempt focused on elements and counts:
// /([A-Z][a-z]*)(\d*)/g
// This needs to be applied iteratively or within a loop that handles groups.
// — Let's reset and use a more standard element-parsing approach —
// A robust parser for chemical formulas is complex.
// For this calculator, let's assume standard input and simplify hydrate handling.
// A common approach: iterate through string, identify element symbols, find numbers after them.
// Parentheses require a stack. Hydrates require special handling.
// — Revised Parsing Strategy —
// Use a stack-based approach for parentheses and a simple iteration for elements.
// Handle hydrates like 'X.Y H2O' by parsing X and Y separately.
// This is a simplified parser. For full chemical formula parsing, libraries are often used.
// Let's assume simple formulas and common hydrates like CuSO4.5H2O
// The current regex handles basic cases. For hydrates, a specific check is needed.
// Let's adjust the initial regex logic slightly to better handle hydrates if they appear as '.'
// The '.' part is handled by match[6] and match[7].
// If we have '.5H2O', match[6] is '.', match[7] is '5'.
// We need to account for H2O atoms. This is tricky with current regex.
// A common simplification: just add up atoms for standard elements.
// For hydrates like X.nH2O: Parse X, then parse nH2O as a separate sub-formula with multiplier n.
// Let's try a different parsing approach:
// 1. Find all element symbols.
// 2. For each symbol, find the count immediately following it, or assume 1.
// 3. Handle parentheses using a stack.
// 4. Handle hydrates by splitting at '.' and processing the second part.
// Re-attempting parsing logic:
// This is a complex task for regex alone without state management.
// Let's use a simpler, iterative approach suitable for typical inputs.
// We are parsing 'parts', which are matches from the regex.
// If we encounter the dot part, we need special handling.
// match[6] = '.', match[7] = number for hydrate multiplier.
if (dot && dotCountStr) {
// This indicates a hydrate part like .5H2O.
// We need to parse the subsequent elements and multiply them by dotCountStr.
// This requires looking ahead or processing the rest of the string.
// Let's assume the format is exactly like "CuSO4.5H2O" and the regex captures '.5'.
// We need to parse 'H2O' after this. This suggests a recursive or stateful parser.
// For simplification, let's parse common hydrate formulas directly.
// E.g., if formula is like "X.nH2O", we can parse X, then parse nH2O.
// The current regex doesn't cleanly separate the '.nH2O' part.
// Let's assume for now that the formula is just elements and numbers,
// and handle hydrates via a specific check or separate parsing logic if the dot is detected.
// Let's refine the initial regex slightly to capture potential hydrate numbers better.
// The current regex: /([A-Z][a-z]*)(\d*)|(\()|(\))(\d*)|(\.)(\d*)/g
// It captures the dot and its number. We need to find 'H2O' or similar after it.
// Simplification: Assume the formula string is structured such that
// elements/counts, open/close parens with counts, and dot/hydrate counts are handled.
// The code currently processes these matches.
// The 'dot' match means we have found a '.'. The 'dotCountStr' is the number after it.
// We still need to parse the subsequent molecule (like H2O).
// Let's modify the logic to handle hydrate part by parsing the remainder.
// This requires a more complex state machine or recursive call.
// A pragmatic approach for this calculator:
// If a '.' is detected, parse the part before it, then parse the part after it.
// Example: "CuSO4.5H2O" -> parse "CuSO4", then parse "5H2O" and multiply its counts by 5.
// The current loop structure processes matches sequentially.
// When match[6] is '.', and match[7] has a number:
// We have a hydrate multiplier. The subsequent elements need to be parsed and multiplied.
// This requires re-evaluating the string from the current position or by splitting.
// Let's restart the parsing logic for clarity, focusing on common formats.
// Elements: [A-Z][a-z]* followed by optional digits.
// Parentheses: (…) followed by optional digits.
// Hydrates: . followed by digits, then a common molecule (like H2O).
// A robust parser is complex. Let's stick to simpler regex that covers most cases
// and add a specific check for common hydrates like .5H2O.
// Okay, let's refine the current approach with a simplified hydrate handling.
// The regex /(?:([A-Z][a-z]*)(\d*))|(?:(\()(\d*)?(\))(\d*)?)|(?:(\.)(\d*))/g
// This regex attempts to capture elements, parens, and hydrate dots.
// Let's use a simpler iterative approach:
// Clear previous parsing state if any mistake was made
elementCounts = {};
totalAtomCount = 0;
multipliers = [1]; // Reset stack
var formulaToParse = formula;
var hydrateMultiplier = 1;
var hydratePart = "";
if (formulaToParse.includes('.')) {
var parts = formulaToParse.split('.', 2); // Split at first dot
formulaToParse = parts[0];
if (parts.length > 1) {
hydratePart = parts[1]; // e.g., "5H2O"
var hydrateMatch = hydratePart.match(/^(\d*)([A-Za-z]+)$/); // Match number and subsequent chars
if (hydrateMatch && hydrateMatch[1]) {
hydrateMultiplier = parseInt(hydrateMatch[1]);
// Assume the rest is H2O or a known molecule type.
// This is a MAJOR simplification. A real parser would need
// to identify the molecule (H2O, etc.) and its internal atoms.
// Let's assume for now it's H2O.
if (hydrateMatch[2].toUpperCase() === 'H2O') {
hydratePart = 'H2O'; // Standardize
} else {
// Handle other hydrate molecules if needed, or throw error
throw new Error("Unsupported hydrate molecule format: " + hydrateMatch[2]);
}
} else {
// If no number before hydrate part, assume 1 (e.g. MgSO4.H2O)
hydrateMultiplier = 1;
hydratePart = hydratePart.match(/^([A-Za-z]+)$/); // Just the molecule name
if (hydratePart && hydratePart[1].toUpperCase() === 'H2O') {
hydratePart = 'H2O';
} else {
throw new Error("Unsupported hydrate molecule format: " + hydratePart);
}
}
}
}
// Parse the main formula part (before the dot)
var elementRegex = /([A-Z][a-z]*)(\d*)/g;
var currentMatch;
while ((currentMatch = elementRegex.exec(formulaToParse)) !== null) {
var symbol = currentMatch[1];
var count = currentMatch[2] ? parseInt(currentMatch[2]) : 1;
if (isNaN(count)) count = 1;
elementCounts[symbol] = (elementCounts[symbol] || 0) + count;
totalAtomCount += count;
}
// Parse the hydrate part if it exists
if (hydratePart) {
if (hydratePart === 'H2O') {
var hCount = 2 * hydrateMultiplier;
var oCount = 1 * hydrateMultiplier;
elementCounts['H'] = (elementCounts['H'] || 0) + hCount;
elementCounts['O'] = (elementCounts['O'] || 0) + oCount;
totalAtomCount += hCount + oCount;
} else {
// Handle other hydrate molecules if parsing logic was implemented
}
}
// Need to handle parentheses within the main part too.
// This requires a more robust parser. Let's integrate a simple stack-based parser.
// — FINAL REVISED PARSING LOGIC (Iterative with Stack for Parentheses) —
elementCounts = {};
totalAtomCount = 0;
multipliers = [1]; // Stack for parenthesis multipliers
var formulaInput = formula.replace(/\s+/g, "); // Remove all whitespace
var hydrateMultiplierBase = 1;
var mainFormulaPart = formulaInput;
// Handle hydrates like X.nH2O or X.H2O
if (formulaInput.includes('.')) {
var hydrateSplit = formulaInput.split('.', 2);
mainFormulaPart = hydrateSplit[0];
var hydrateSuffix = hydrateSplit[1];
var hydrateMatch = hydrateSuffix.match(/^(\d*)(H2O)$/i); // Expecting number then H2O
if (hydrateMatch) {
hydrateMultiplierBase = hydrateMatch[1] ? parseInt(hydrateMatch[1]) : 1;
// Parse H2O atoms and add them multiplied
elementCounts['H'] = (elementCounts['H'] || 0) + (2 * hydrateMultiplierBase);
elementCounts['O'] = (elementCounts['O'] || 0) + (1 * hydrateMultiplierBase);
totalAtomCount += (3 * hydrateMultiplierBase); // Total atoms in the hydrate part
} else {
// Handle other possible hydrate formats or throw error
throw new Error("Unsupported hydrate format. Expected '.nH2O'");
}
}
// Parse the main formula part (handling elements, counts, and parentheses)
var i = 0;
while (i < mainFormulaPart.length) {
// Check for opening parenthesis
if (mainFormulaPart[i] === '(') {
i++;
var numMultiplier = 1;
var numStr = "";
while (i 1) {
multipliers.pop();
} else {
throw new Error("Mismatched parentheses: unexpected ')'");
}
}
// Check for element symbol
else if (/[A-Z]/.test(mainFormulaPart[i])) {
var symbol = mainFormulaPart[i];
i++;
// Check for second lowercase letter
if (i < mainFormulaPart.length && /[a-z]/.test(mainFormulaPart[i])) {
symbol += mainFormulaPart[i];
i++;
}
var countStr = "";
while (i 1) {
throw new Error("Mismatched parentheses: unclosed '('");
}
// Use provided custom masses if available, otherwise use defaults
for (var symbol in elementCounts) {
var mass = customMasses[symbol] || atomicMasses[symbol];
if (!mass) {
throw new Error("Atomic mass for element '" + symbol + "' not found. Please provide it in the custom masses field.");
}
var contribution = elementCounts[symbol] * mass;
elementsInFormula[symbol] = {
count: elementCounts[symbol],
mass: mass,
contribution: contribution
};
formulaWeightResult += contribution;
}
// Adjust formulaWeightResult for the hydrate part that was added directly
// This logic needs to be integrated correctly.
// The current approach adds hydrate atoms directly, so formulaWeightResult should be correct.
return true; // Parsing successful
} // End of revised parsing attempt
function validateInput() {
var formulaInput = document.getElementById('chemicalFormula');
var formulaError = document.getElementById('chemicalFormulaError');
var customMassesInput = document.getElementById('elementMasses');
var customMassesError = document.getElementById('elementMassesError');
var isValid = true;
formulaError.textContent = ";
formulaError.style.display = 'none';
customMassesError.textContent = ";
customMassesError.style.display = 'none';
if (formulaInput.value.trim() === ") {
formulaError.textContent = 'Chemical formula cannot be empty.';
formulaError.style.display = 'block';
isValid = false;
}
// Validate custom masses format
var customMassesValue = customMassesInput.value.trim();
if (customMassesValue) {
var pairs = customMassesValue.split(',');
for (var i = 0; i < pairs.length; i++) {
var pair = pairs[i].trim().split(':');
if (pair.length !== 2) {
customMassesError.textContent = 'Invalid format. Use "Symbol: Mass".';
customMassesError.style.display = 'block';
isValid = false;
break;
}
var symbol = pair[0].trim();
var mass = parseFloat(pair[1].trim());
if (!symbol || isNaN(mass) || mass <= 0) {
customMassesError.textContent = 'Invalid symbol or mass value.';
customMassesError.style.display = 'block';
isValid = false;
break;
}
if (!/^[A-Z][a-z]?$/.test(symbol)) {
customMassesError.textContent = 'Invalid element symbol format.';
customMassesError.style.display = 'block';
isValid = false;
break;
}
}
}
// Attempt to parse to catch formula format errors early
try {
if (isValid && formulaInput.value.trim()) {
parseChemicalFormula(formulaInput.value); // This will throw error if format is bad
}
} catch (e) {
formulaError.textContent = e.message;
formulaError.style.display = 'block';
isValid = false;
}
return isValid;
}
function calculateFormulaWeight() {
if (!validateInput()) {
return;
}
var formula = document.getElementById('chemicalFormula').value;
try {
parseChemicalFormula(formula); // Ensure parsing happens and populates global vars
document.getElementById('mainResult').textContent = formulaWeightResult.toFixed(3) + ' g/mol';
document.getElementById('formulaWeight').innerHTML = 'Formula Weight: ' + formulaWeightResult.toFixed(3) + ' g/mol';
document.getElementById('totalAtoms').innerHTML = 'Total Atoms: ' + totalAtomCount;
var breakdownString = "";
var sortedSymbols = Object.keys(elementsInFormula).sort();
for (var i = 0; i < sortedSymbols.length; i++) {
var symbol = sortedSymbols[i];
breakdownString += symbol + ": " + elementsInFormula[symbol].count + (i < sortedSymbols.length – 1 ? ", " : "");
}
document.getElementById('elementBreakdown').innerHTML = 'Element Breakdown: ' + breakdownString;
updateTableAndChart();
} catch (e) {
document.getElementById('chemicalFormulaError').textContent = e.message;
document.getElementById('chemicalFormulaError').style.display = 'block';
// Clear results if parsing fails
document.getElementById('mainResult').textContent = '–';
document.getElementById('formulaWeight').innerHTML = 'Formula Weight: — g/mol';
document.getElementById('totalAtoms').innerHTML = 'Total Atoms: –';
document.getElementById('elementBreakdown').innerHTML = 'Element Breakdown: –';
clearTableAndChart();
}
}
function updateTableAndChart() {
var tableBody = document.getElementById('atomicMassTable').getElementsByTagName('tbody')[0];
tableBody.innerHTML = "; // Clear previous rows
chartData = [];
var chartLegendHtml = 'Legend: ';
var legendItems = [];
var sortedSymbols = Object.keys(elementsInFormula).sort();
for (var i = 0; i < sortedSymbols.length; i++) {
var symbol = sortedSymbols[i];
var data = elementsInFormula[symbol];
var row = tableBody.insertRow();
row.insertCell(0).textContent = symbol;
row.insertCell(1).textContent = data.mass.toFixed(3);
row.insertCell(2).textContent = data.count;
row.insertCell(3).textContent = data.contribution.toFixed(3);
chartData.push({
label: symbol,
value: data.contribution,
mass: data.mass.toFixed(3),
count: data.count
});
legendItems.push('' + symbol + ' (' + data.contribution.toFixed(3) + ' g/mol)');
}
document.getElementById('chart-legend').innerHTML = legendItems.join(");
drawChart();
}
function clearTableAndChart() {
var tableBody = document.getElementById('atomicMassTable').getElementsByTagName('tbody')[0];
tableBody.innerHTML = ";
chartData = [];
document.getElementById('chart-legend').innerHTML = ";
if (chartInstance) {
chartInstance.destroy();
chartInstance = null;
}
var ctx = document.getElementById('atomicMassChart').getContext('2d');
ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
}
function drawChart() {
var ctx = document.getElementById('atomicMassChart').getContext('2d');
if (chartInstance) {
chartInstance.destroy(); // Destroy previous chart if exists
}
if (chartData.length === 0) return;
// Generate random colors for each data point
var colors = [];
var hoverColors = [];
for (var i = 0; i item.label + ' (' + item.contribution + ' g/mol)'),
datasets: [{
data: chartData.map(item => item.value),
backgroundColor: colors,
hoverBackgroundColor: hoverColors,
borderWidth: 1,
borderColor: '#fff'
}]
},
options: {
responsive: true,
maintainAspectRatio: true, // Adjust aspect ratio if needed
plugins: {
legend: {
display: false // Legend is handled separately for better control
},
tooltip: {
callbacks: {
label: function(tooltipItem) {
var item = chartData[tooltipItem.dataIndex];
return item.label + ': ' + item.value.toFixed(3) + ' g/mol (' + item.count + ' atoms, atomic mass: ' + item.mass + ' g/mol)';
}
}
}
}
}
});
}
// Helper function to generate consistent random colors based on label
function getRandomColor(label) {
var hash = 0;
for (var i = 0; i < label.length; i++) {
hash = label.charCodeAt(i) + ((hash << 5) – hash);
}
var color = '#';
for (var i = 0; i > (i * 8)) & 0xFF;
color += ('00' + value.toString(16)).substr(-2);
}
// Ensure sufficient contrast / avoid very dark colors if needed
var rgb = parseInt(color.substring(1), 16); // convert rrggbb to decimal
var r = (rgb >> 16) & 0xff;
var g = (rgb >> 8) & 0xff;
var b = (rgb >> 0) & 0xff;
var luma = 0.2126 * r + 0.7152 * g + 0.0722 * b; // per ITU-L.42
if (luma < 40) { // If color is too dark, make it lighter
color = '#' + ('000000' + (rgb + 0x555555).toString(16)).slice(-6);
}
return color;
}
// Helper to lighten a hex color
function lightenColor(hex, percent) {
percent = percent || 20;
var r = parseInt(hex.slice(1, 3), 16),
g = parseInt(hex.slice(3, 5), 16),
b = parseInt(hex.slice(5, 7), 16);
r = Math.round(Math.min(255, r + (255 – r) * percent / 100));
g = Math.round(Math.min(255, g + (255 – g) * percent / 100));
b = Math.round(Math.min(255, b + (255 – b) * percent / 100));
return "#" + r.toString(16).padStart(2, '0') + g.toString(16).padStart(2, '0') + b.toString(16).padStart(2, '0');
}
function resetCalculator() {
document.getElementById('chemicalFormula').value = 'H2O';
document.getElementById('elementMasses').value = '';
document.getElementById('chemicalFormulaError').textContent = '';
document.getElementById('chemicalFormulaError').style.display = 'none';
document.getElementById('elementMassesError').textContent = '';
document.getElementById('elementMassesError').style.display = 'none';
// Reset results
document.getElementById('mainResult').textContent = '–';
document.getElementById('formulaWeight').innerHTML = 'Formula Weight: — g/mol';
document.getElementById('totalAtoms').innerHTML = 'Total Atoms: –';
document.getElementById('elementBreakdown').innerHTML = 'Element Breakdown: –';
clearTableAndChart();
// Optionally call calculate to show default value results
calculateFormulaWeight();
}
function copyResults() {
var mainResult = document.getElementById('mainResult').textContent;
var formulaWeight = document.getElementById('formulaWeight').textContent.replace('Formula Weight: ', ");
var totalAtoms = document.getElementById('totalAtoms').textContent.replace('Total Atoms: ', ");
var breakdown = document.getElementById('elementBreakdown').textContent.replace('Element Breakdown: ', ");
var assumptions = "Key Assumptions:\n";
assumptions += "- Standard atomic masses used.\n";
assumptions += "- Formula entered is accurate.\n";
var textToCopy = "Formula Weight Calculation Results:\n\n";
textToCopy += "Chemical Formula: " + document.getElementById('chemicalFormula').value + "\n";
textToCopy += "Formula Weight: " + formulaWeight + "\n";
textToCopy += "Total Atoms: " + totalAtoms + "\n";
textToCopy += "Element Breakdown: " + breakdown + "\n\n";
textToCopy += assumptions;
// Attempt to copy to clipboard
if (navigator.clipboard && window.isSecureContext) {
navigator.clipboard.writeText(textToCopy).then(function() {
// Success feedback
var copyButton = document.getElementById('copyBtn');
var originalText = copyButton.textContent;
copyButton.textContent = 'Copied!';
setTimeout(function() {
copyButton.textContent = originalText;
}, 2000);
}).catch(function(err) {
console.error('Failed to copy text: ', err);
// Fallback for older browsers or insecure contexts
copyFallback(textToCopy);
});
} else {
// Fallback for older browsers or insecure contexts
copyFallback(textToCopy);
}
}
function copyFallback(text) {
var textArea = document.createElement("textarea");
textArea.value = text;
// Avoid scrolling to bottom
textArea.style.position = "fixed";
textArea.style.top = "0";
textArea.style.left = "0";
textArea.style.width = "2em";
textArea.style.height = "2em";
textArea.style.padding = "0";
textArea.style.border = "none";
textArea.style.outline = "none";
textArea.style.boxShadow = "none";
textArea.style.background = "transparent";
document.body.appendChild(textArea);
textArea.focus();
textArea.select();
try {
var successful = document.execCommand('copy');
var msg = successful ? 'Copied!' : 'Copy failed!';
// Provide feedback
var copyButton = document.getElementById('copyBtn');
var originalText = copyButton.textContent;
copyButton.textContent = msg;
setTimeout(function() {
copyButton.textContent = originalText;
}, 2000);
} catch (err) {
console.error('Fallback copy failed: ', err);
var copyButton = document.getElementById('copyBtn');
var originalText = copyButton.textContent;
copyButton.textContent = 'Copy failed!';
setTimeout(function() {
copyButton.textContent = originalText;
}, 2000);
}
document.body.removeChild(textArea);
}
// Initialize with default value
window.onload = function() {
document.getElementById('chemicalFormula').value = 'H2O';
calculateFormulaWeight();
// Setup FAQ accordion behavior
var faqHeaders = document.querySelectorAll('.faq-item strong');
for (var i = 0; i < faqHeaders.length; i++) {
faqHeaders[i].addEventListener('click', function() {
var content = this.nextElementSibling;
var isVisible = content.style.display === 'block';
// Close all others first
var allContents = document.querySelectorAll('.faq-item p');
for(var j=0; j < allContents.length; j++) {
allContents[j].style.display = 'none';
}
// Toggle the clicked one
if (!isVisible) {
content.style.display = 'block';
}
});
}
};