Acid Concentration [HA] = ${acidConc.toExponential(4)} M
Conjugate Base Concentration [A-] = ${conjugateConc.toExponential(4)} M
Temperature = ${temperature.toFixed(1)} °C
`;
if (bufferCapacity) {
result += `
Buffer Capacity (β) = ${bufferCapacity.toExponential(4)} mol/L
This represents the amount of strong acid or base that can be added before causing a significant pH change.
`;
}
// Add interpretation
const phDiff = Math.abs(ph - pka);
if (phDiff <= 1) {
result += `
Interpretation: This solution functions as an effective buffer since the pH (${ph.toFixed(2)}) is within 1 unit of the pKa (${pka.toFixed(2)}).
`;
} else {
result += `
Interpretation: This solution is not an optimal buffer since the pH (${ph.toFixed(2)}) differs from the pKa (${pka.toFixed(2)}) by more than 1 unit.
`;
}
} else if (calcType === 'pKa-pH') {
// Calculate pKa from pH and concentrations
ph = parseFloat(phInput.value);
acidConc = parseFloat(acidInput.value);
conjugateConc = parseFloat(conjugateInput.value);
// Calculate pKa using Henderson-Hasselbalch equation rearranged
ratio = conjugateConc / acidConc;
pka = ph - Math.log10(ratio);
// Calculate Ka
const ka = Math.pow(10, -pka);
// Create result output
result = `
For a system with pH = ${ph.toFixed(2)} and [A-]/[HA] = ${ratio.toFixed(4)}, the calculated pKa is:
pKa = ${pka.toFixed(4)}
Acid Dissociation Constant (Ka) = ${ka.toExponential(4)}
Acid Concentration [HA] = ${acidConc.toExponential(4)} M
Conjugate Base Concentration [A-] = ${conjugateConc.toExponential(4)} M
Temperature = ${temperature.toFixed(1)} °C
`;
// Add interpretation based on pKa value
if (pka < 0) {
result += `
Interpretation: This is a strong acid (pKa < 0).
`;
} else if (pka < 4) {
result += `
Interpretation: This is a moderately strong acid (0 < pKa < 4).
`;
} else if (pka < 10) {
result += `
Interpretation: This is a weak acid (4 < pKa < 10).
`;
} else {
result += `
Interpretation: This is a very weak acid (pKa > 10).
`;
}
} else if (calcType === 'concentration') {
// Calculate concentrations from pH and pKa
ph = parseFloat(phInput.value);
pka = parseFloat(pkaInput.value);
acidConc = parseFloat(acidInput.value);
conjugateConc = parseFloat(conjugateInput.value);
// Henderson-Hasselbalch: pH = pKa + log([A-]/[HA])
// Rearrange to get [A-]/[HA] = 10^(pH-pKa)
ratio = Math.pow(10, ph - pka);
if (!isNaN(acidConc)) {
// Calculate conjugate base concentration
conjugateConc = acidConc * ratio;
result = `
For a system with pH = ${ph.toFixed(2)}, pKa = ${pka.toFixed(2)}, and [HA] = ${acidConc.toExponential(4)} M:
Conjugate Base Concentration [A-] = ${conjugateConc.toExponential(4)} M
Ratio [A-]/[HA] = ${ratio.toFixed(4)}
`;
} else if (!isNaN(conjugateConc)) {
// Calculate acid concentration
acidConc = conjugateConc / ratio;
result = `
For a system with pH = ${ph.toFixed(2)}, pKa = ${pka.toFixed(2)}, and [A-] = ${conjugateConc.toExponential(4)} M:
Acid Concentration [HA] = ${acidConc.toExponential(4)} M
Ratio [A-]/[HA] = ${ratio.toFixed(4)}
`;
}
// Add temperature information
result += `
Temperature = ${temperature.toFixed(1)} °C
`;
// Add buffer information
const phDiff = Math.abs(ph - pka);
if (phDiff <= 1) {
// Calculate buffer capacity
bufferCapacity = (2.303 * acidConc * conjugateConc) / (acidConc + conjugateConc);
result += `
Buffer Properties:
This solution functions as an effective buffer since the pH (${ph.toFixed(2)}) is within 1 unit of the pKa (${pka.toFixed(2)}).
Buffer Capacity (β) = ${bufferCapacity.toExponential(4)} mol/L
`;
} else {
result += `
Buffer Properties: This solution is not an optimal buffer since the pH (${ph.toFixed(2)}) differs from the pKa (${pka.toFixed(2)}) by more than 1 unit.
`;
}
}
// Display results
resultsContent.innerHTML = result;
resultsSection.style.display = 'block';
}
// Reset button click
resetBtn.addEventListener('click', function() {
// Clear all inputs
pkaInput.value = '';
phInput.value = '';
acidInput.value = '';
conjugateInput.value = '';
temperatureInput.value = '25';
// Hide results
resultsSection.style.display = 'none';
// Hide error messages
pkaError.style.display = 'none';
phError.style.display = 'none';
acidError.style.display = 'none';
conjugateError.style.display = 'none';
temperatureError.style.display = 'none';
// Reset to default calculation type
calculationType.value = 'pH-pKa';
updateInputVisibility();
});
// PDF Download functionality
downloadBtn.addEventListener('click', function() {
// Show loading
loadingElement.style.display = 'block';
const { jsPDF } = window.jspdf;
// Create PDF
setTimeout(() => {
generatePDF();
loadingElement.style.display = 'none';
}, 500);
});
// Reference table download
referenceDownloadBtn.addEventListener('click', function() {
// Show loading
loadingElement.style.display = 'block';
const { jsPDF } = window.jspdf;
// Create PDF with reference table
setTimeout(() => {
generateReferencePDF();
loadingElement.style.display = 'none';
}, 500);
});
// Generate PDF with calculation results
function generatePDF() {
const { jsPDF } = window.jspdf;
const doc = new jsPDF();
// Set PDF properties and colors to match the web app
doc.setTextColor(52, 152, 219); // Primary color
doc.setFontSize(22);
doc.text('pKa Calculator Results', 105, 20, { align: 'center' });
doc.setTextColor(41, 128, 185); // Secondary color
doc.setFontSize(14);
doc.text('Calculation Details', 20, 35);
doc.setTextColor(51, 51, 51); // Text color
doc.setFontSize(12);
// Get calculation details
const calcType = calculationType.value;
let detailsText = '';
if (calcType === 'pH-pKa') {
detailsText = `Calculation Type: pH from pKa and concentrations
pKa Value: ${pkaInput.value}
Acid Concentration [HA]: ${acidInput.value || 'N/A'} M
Conjugate Base [A-]: ${conjugateInput.value || 'N/A'} M
Temperature: ${temperatureInput.value} °C`;
} else if (calcType === 'pKa-pH') {
detailsText = `Calculation Type: pKa from pH and concentrations
pH Value: ${phInput.value}
Acid Concentration [HA]: ${acidInput.value} M
Conjugate Base [A-]: ${conjugateInput.value} M
Temperature: ${temperatureInput.value} °C`;
} else if (calcType === 'concentration') {
detailsText = `Calculation Type: Concentrations from pH and pKa
pH Value: ${phInput.value}
pKa Value: ${pkaInput.value}
${acidInput.value ? 'Acid Concentration [HA]: ' + acidInput.value + ' M' : ''}
${conjugateInput.value ? 'Conjugate Base [A-]: ' + conjugateInput.value + ' M' : ''}
Temperature: ${temperatureInput.value} °C`;
}
// Add details to PDF
const detailsLines = detailsText.split('\n');
let y = 45;
detailsLines.forEach(line => {
doc.text(line, 20, y);
y += 8;
});
// Add a blue line separator
doc.setDrawColor(52, 152, 219);
doc.setLineWidth(0.5);
doc.line(20, y, 190, y);
y += 10;
// Add results section
doc.setTextColor(41, 128, 185);
doc.setFontSize(14);
doc.text('Results', 20, y);
y += 10;
doc.setTextColor(51, 51, 51);
doc.setFontSize(12);
// Get result text (simplified version of what's shown in the web app)
const resultText = resultsContent.innerText.replace(/\n\s*\n/g, '\n');
const resultLines = resultText.split('\n');
resultLines.forEach(line => {
// Check if we need a new page
if (y > 270) {
doc.addPage();
y = 20;
}
// Check if this is a main result value
if (line.includes('pH =') || line.includes('pKa =') || line.includes('Concentration')) {
doc.setTextColor(41, 128, 185);
doc.setFontSize(13);
} else {
doc.setTextColor(51, 51, 51);
doc.setFontSize(12);
}
doc.text(line, 20, y);
y += 8;
});
// Add footer with date
const date = new Date().toLocaleDateString();
y = 285;
doc.setTextColor(150, 150, 150);
doc.setFontSize(10);
doc.text(`Generated on ${date}`, 105, y, { align: 'center' });
// Save the PDF
doc.save('pKa_calculation_results.pdf');
}
// Generate PDF with reference table
function generateReferencePDF() {
const { jsPDF } = window.jspdf;
const doc = new jsPDF();
// Set PDF properties
doc.setTextColor(52, 152, 219);
doc.setFontSize(22);
doc.text('Common pKa Values Reference', 105, 20, { align: 'center' });
// Define table data
const tableData = [
['Acid', 'Formula', 'pKa', 'Acid Strength'],
['Hydroiodic acid', 'HI', '-10', 'Strong'],
['Hydrobromic acid', 'HBr', '-9', 'Strong'],
['Hydrochloric acid', 'HCl', '-7', 'Strong'],
['Sulfuric acid (1st)', 'H₂SO₄', '-3', 'Strong'],
['Nitric acid', 'HNO₃', '-1.3', 'Strong'],
['Hydronium ion', 'H₃O⁺', '0', 'Strong'],
['Sulfuric acid (2nd)', 'HSO₄⁻', '1.9', 'Weak'],
['Phosphoric acid (1st)', 'H₃PO₄', '2.1', 'Weak'],
['Formic acid', 'HCOOH', '3.8', 'Weak'],
['Acetic acid', 'CH₃COOH', '4.8', 'Weak'],
['Carbonic acid (1st)', 'H₂CO₃', '6.4', 'Weak'],
['Phosphoric acid (2nd)', 'H₂PO₄⁻', '7.2', 'Weak'],
['Hydrogen sulfide (1st)', 'H₂S', '7.0', 'Weak'],
['Ammonium ion', 'NH₄⁺', '9.2', 'Weak'],
['Carbonic acid (2nd)', 'HCO₃⁻', '10.3', 'Weak'],
['Phosphoric acid (3rd)', 'HPO₄²⁻', '12.3', 'Weak'],
['Phenol', 'C₆H₅OH', '10.0', 'Weak'],
['Hydrogen sulfide (2nd)', 'HS⁻', '12.9', 'Weak'],
['Water', 'H₂O', '15.7', 'Very Weak'],
['Ethanol', 'C₂H₅OH', '16.0', 'Very Weak'],
['Ammonia', 'NH₃', '38', 'Extremely Weak'],
['Methane', 'CH₄', '50', 'Extremely Weak']
];
// Create table
let y = 30;
const firstPageRows = 17; // Number of rows that fit on first page
// Table header in primary color
doc.setFillColor(52, 152, 219);
doc.setTextColor(255, 255, 255);
doc.setFontSize(12);
// Header row
doc.rect(20, y, 50, 10, 'F');
doc.rect(70, y, 30, 10, 'F');
doc.rect(100, y, 30, 10, 'F');
doc.rect(130, y, 50, 10, 'F');
doc.text(tableData[0][0], 22, y + 6);
doc.text(tableData[0][1], 72, y + 6);
doc.text(tableData[0][2], 102, y + 6);
doc.text(tableData[0][3], 132, y + 6);
y += 10;
// Table content
doc.setTextColor(51, 51, 51);
// First page
for (let i = 1; i <= firstPageRows && i < tableData.length; i++) {
// Alternate row background
if (i % 2 === 0) {
doc.setFillColor(240, 240, 240);
doc.rect(20, y, 160, 10, 'F');
}
doc.text(tableData[i][0], 22, y + 6);
doc.text(tableData[i][1], 72, y + 6);
doc.text(tableData[i][2], 102, y + 6);
doc.text(tableData[i][3], 132, y + 6);
// Draw cell borders
doc.setDrawColor(200, 200, 200);
doc.rect(20, y, 50, 10);
doc.rect(70, y, 30, 10);
doc.rect(100, y, 30, 10);
doc.rect(130, y, 50, 10);
y += 10;
}
// Add second page if needed
if (tableData.length > firstPageRows + 1) {
doc.addPage();
y = 20;
// Continue with the table header
doc.setFillColor(52, 152, 219);
doc.setTextColor(255, 255, 255);
doc.rect(20, y, 50, 10, 'F');
doc.rect(70, y, 30, 10, 'F');
doc.rect(100, y, 30, 10, 'F');
doc.rect(130, y, 50, 10, 'F');
doc.text(tableData[0][0], 22, y + 6);
doc.text(tableData[0][1], 72, y + 6);
doc.text(tableData[0][2], 102, y + 6);
doc.text(tableData[0][3], 132, y + 6);
y += 10;
// Continue with remaining rows
doc.setTextColor(51, 51, 51);
for (let i = firstPageRows + 1; i < tableData.length; i++) {
// Alternate row background
if (i % 2 === 0) {
doc.setFillColor(240, 240, 240);
doc.rect(20, y, 160, 10, 'F');
}
doc.text(tableData[i][0], 22, y + 6);
doc.text(tableData[i][1], 72, y + 6);
doc.text(tableData[i][2], 102, y + 6);
doc.text(tableData[i][3], 132, y + 6);
// Draw cell borders
doc.setDrawColor(200, 200, 200);
doc.rect(20, y, 50, 10);
doc.rect(70, y, 30, 10);
doc.rect(100, y, 30, 10);
doc.rect(130, y, 50, 10);
y += 10;
}
}
// Add information section
y += 10;
doc.setTextColor(41, 128, 185);
doc.setFontSize(14);
doc.text('Information about pKa', 20, y);
y += 10;
doc.setTextColor(51, 51, 51);
doc.setFontSize(12);
const infoText = [
"• The pKa value represents the negative logarithm of the acid dissociation constant (Ka).",
"• pKa = -log₁₀(Ka)",
"• Lower pKa values indicate stronger acids (more readily donate protons).",
"• pKa values are typically affected by temperature and solvent.",
"• For buffer solutions, optimal buffering occurs when pH ≈ pKa (±1 unit)."
];
infoText.forEach(line => {
doc.text(line, 20, y);
y += 8;
});
// Add footer with date
const date = new Date().toLocaleDateString();
y = 285;
doc.setTextColor(150, 150, 150);
doc.setFontSize(10);
doc.text(`Generated on ${date}`, 105, y, { align: 'center' });
// Save the PDF
doc.save('pKa_reference_table.pdf');
}
});
