pH Calculator
body {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
line-height: 1.6;
color: #333;
background-color: #f8f9fa;
margin: 0;
padding: 20px;
}
.calculator-container {
max-width: 700px;
margin: 30px auto;
background-color: #ffffff;
padding: 30px;
border-radius: 8px;
box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
border: 1px solid #e0e0e0;
}
.calculator-header {
text-align: center;
margin-bottom: 30px;
padding-bottom: 15px;
border-bottom: 2px solid #004a99;
}
.calculator-header h1 {
color: #004a99;
margin-bottom: 5px;
}
.calculator-header p {
color: #555;
font-size: 1.1em;
}
.input-section, .result-section {
margin-bottom: 25px;
padding: 20px;
border: 1px solid #dcdcdc;
border-radius: 5px;
background-color: #fdfdfd;
}
.input-group {
margin-bottom: 15px;
display: flex;
align-items: center;
flex-wrap: wrap; /* Allows wrapping on smaller screens */
}
.input-group label {
flex: 1 1 150px; /* Flex basis for labels */
min-width: 120px; /* Minimum width for labels */
margin-right: 15px;
font-weight: 500;
color: #004a99;
font-size: 1.05em;
}
.input-group input[type="number"] {
flex: 2 1 200px; /* Flex basis for inputs */
padding: 10px 12px;
border: 1px solid #ccc;
border-radius: 4px;
font-size: 1em;
box-sizing: border-box; /* Include padding and border in element's total width and height */
}
.input-group input[type="number"]:focus {
border-color: #007bff;
outline: none;
box-shadow: 0 0 0 2px rgba(0, 123, 255, 0.25);
}
.button-group {
text-align: center;
margin-top: 25px;
}
.button-group button {
background-color: #28a745;
color: white;
border: none;
padding: 12px 25px;
border-radius: 5px;
font-size: 1.1em;
cursor: pointer;
transition: background-color 0.3s ease;
margin: 5px;
}
.button-group button:hover {
background-color: #218838;
}
.result-section {
text-align: center;
background-color: #e9ecef;
border-color: #ced4da;
}
.result-section h3 {
color: #004a99;
margin-bottom: 15px;
font-size: 1.3em;
}
#calculationResult {
font-size: 2.2em;
font-weight: bold;
color: #28a745;
padding: 15px;
background-color: #ffffff;
border: 1px dashed #004a99;
border-radius: 6px;
display: inline-block;
min-width: 150px; /* Ensures minimum width for the result */
margin-top: 10px;
}
.explanation-section {
margin-top: 40px;
padding: 30px;
background-color: #ffffff;
border-radius: 8px;
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}
.explanation-section h2 {
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border-bottom: 2px solid #004a99;
padding-bottom: 10px;
margin-bottom: 20px;
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.explanation-section h3 {
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margin-top: 20px;
margin-bottom: 10px;
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.explanation-section p, .explanation-section ul {
margin-bottom: 15px;
color: #444;
}
.explanation-section code {
background-color: #e9ecef;
padding: 2px 6px;
border-radius: 3px;
font-family: Consolas, Monaco, 'Andale Mono', 'Ubuntu Mono', monospace;
}
/* Responsive adjustments */
@media (max-width: 600px) {
.input-group {
flex-direction: column;
align-items: stretch;
}
.input-group label {
margin-right: 0;
margin-bottom: 8px;
text-align: left;
}
.input-group input[type="number"] {
width: 100%;
margin-bottom: 10px; /* Add space between stacked inputs */
}
.calculator-container {
padding: 20px;
}
#calculationResult {
font-size: 1.8em;
min-width: unset;
width: 80%;
box-sizing: border-box;
}
.button-group button {
padding: 10px 20px;
font-size: 1em;
}
}
Understanding the pH Scale and Calculation
The pH scale is a fundamental concept in chemistry used to measure the acidity or alkalinity of an aqueous solution. It is a logarithmic scale, meaning each whole number change in pH represents a tenfold change in the hydrogen ion concentration.
What is pH?
pH is defined as the negative logarithm (base 10) of the hydrogen ion activity, which in dilute solutions is approximately equal to the molar concentration of hydrogen ions ([H+]). The formula is:
pH = -log10[H+]
- pH < 7: Acidic solution (higher [H+])
- pH = 7: Neutral solution (at 25°C)
- pH > 7: Alkaline (or basic) solution (lower [H+])
How the Calculator Works
This calculator performs two primary functions:
- Calculating pH from Hydrogen Ion Concentration: Given the molar concentration of hydrogen ions ([H+]) in moles per liter (mol/L), the calculator applies the formula
pH = -log10[H+] to determine the pH value.
- Calculating Hydrogen Ion Concentration from pH: Given a pH value, the calculator rearranges the formula to find the hydrogen ion concentration. The inverse logarithm (antilogarithm) is used:
[H+] = 10-pH.
Using the Calculator
1. To find pH: Enter the concentration of hydrogen ions in mol/L (e.g., 1.0e-7 for a neutral solution) into the "Hydrogen Ion Concentration" field and click "Calculate pH".
2. To find [H+]: Enter the pH value into the "Hydrogen Ion Concentration" field (the calculator treats this input as pH when calculating [H+]) and click "Calculate [H+]".
3. Click "Reset" to clear all fields.
Real-World Examples
- Acidic Solution: If you have a solution with a hydrogen ion concentration of
0.01 mol/L (or 1.0e-2 mol/L), the calculator will show: pH = -log(0.01) = 2.0. This indicates a highly acidic substance like lemon juice.
- Neutral Solution: Pure water at 25°C has a hydrogen ion concentration of approximately
1.0e-7 mol/L. The calculator will yield: pH = -log(1.0e-7) = 7.0.
- Alkaline Solution: If a substance has a pH of 10.0, entering 10 into the field and clicking "Calculate [H+]" will show: [H+] = 10-10 mol/L. This is characteristic of substances like baking soda.
Importance of pH Measurement
pH is critical in various fields, including:
- Environmental Science: Monitoring the pH of water bodies (rivers, lakes) and soil for ecosystem health.
- Biology: Maintaining specific pH levels within cells and biological fluids (like blood) is essential for life.
- Food Science: Controlling pH affects food preservation, taste, and texture.
- Industrial Processes: Many chemical manufacturing processes require precise pH control.
function calculatePH() {
var concentrationInput = document.getElementById("hydrogenIonConcentration").value;
var resultDisplay = document.getElementById("calculationResult");
if (concentrationInput === "") {
resultDisplay.textContent = "Enter value";
return;
}
var concentration = parseFloat(concentrationInput);
if (isNaN(concentration) || concentration <= 0) {
resultDisplay.textContent = "Invalid [H+]";
return;
}
var ph = -Math.log10(concentration);
resultDisplay.textContent = ph.toFixed(2); // Display pH with 2 decimal places
}
function calculateConcentration() {
var phInput = document.getElementById("hydrogenIonConcentration").value;
var resultDisplay = document.getElementById("calculationResult");
if (phInput === "") {
resultDisplay.textContent = "Enter value";
return;
}
var ph = parseFloat(phInput);
if (isNaN(ph)) {
resultDisplay.textContent = "Invalid pH";
return;
}
// Handle potential issues with very large negative pH values (though unlikely in real scenarios)
// Ensure the exponent is within reasonable limits for Math.pow or equivalent
if (ph 20) { // Arbitrary practical limits for pH
resultDisplay.textContent = "pH out of range";
return;
}
var concentration = Math.pow(10, -ph);
resultDisplay.textContent = concentration.toExponential(2) + " mol/L"; // Display in scientific notation
}
function resetForm() {
document.getElementById("hydrogenIonConcentration").value = "";
document.getElementById("calculationResult").textContent = "–";
}