Calculating Moles Worksheet

Moles Calculation Worksheet & Calculator

Mass to Moles Converter

Enter the mass of the substance and its molar mass to find the number of moles.

Particles to Moles Converter

Convert number of atoms or molecules to moles using Avogadro's number ($6.022 \times 10^{23}$).

Use scientific notation like 1.2e24 for $1.2 \times 10^{24}$

Understanding Mole Calculations

In chemistry, the mole is the standard unit used to measure the amount of a substance. Just as a "dozen" refers to 12 items, one mole refers to exactly $6.02214076 \times 10^{23}$ particles. This massive number is known as Avogadro's Number ($N_A$).

The Basic Formula

To calculate moles from a given mass, we use the fundamental formula:

n = m / M

• n = Amount in moles (mol)
• m = Mass of the substance in grams (g)
• M = Molar mass of the substance (g/mol)

How to Use This Worksheet

Whether you are a student finishing a chemistry assignment or a professional in a lab, calculating moles involves three main steps:

1. Identify the Mass: Weigh your sample in grams.
2. Determine Molar Mass: Sum the atomic masses of all atoms in the chemical formula using the periodic table. For example, $H_2O$ has a molar mass of approximately 18.015 g/mol (1.008 + 1.008 + 15.999).
3. Divide: Divide the mass by the molar mass to get the number of moles.

Example Calculation

Question: How many moles are in 50 grams of Sodium Chloride (NaCl)?

Step 1: Mass (m) = 50g

Step 2: Molar Mass of NaCl = 22.99 (Na) + 35.45 (Cl) = 58.44 g/mol

Step 3: $n = 50 / 58.44 = 0.8556$ moles.

Converting Particles to Moles

If you are given the total number of atoms or molecules instead of mass, use Avogadro's number:

n = N / N_A

Where N is the number of particles and N_A is $6.022 \times 10^{23}$. This is essential for understanding the scale of chemical reactions at the molecular level.

function calculateMoles() { var mass = parseFloat(document.getElementById('massInput').value); var molarMass = parseFloat(document.getElementById('molarMassInput').value); var resultDiv = document.getElementById('moleResult'); if (isNaN(mass) || isNaN(molarMass) || molarMass <= 0) { resultDiv.style.display = 'block'; resultDiv.style.backgroundColor = '#fdeded'; resultDiv.style.color = '#c0392b'; resultDiv.innerHTML = 'Please enter valid positive numbers for mass and molar mass.'; return; } var moles = mass / molarMass; resultDiv.style.display = 'block'; resultDiv.style.backgroundColor = '#e8f4fd'; resultDiv.style.color = '#2980b9'; resultDiv.innerHTML = 'Result: ' + moles.toFixed(4) + ' moles'; } function calculateFromParticles() { var particlesStr = document.getElementById('particleInput').value; var particles = parseFloat(particlesStr); var avogadro = 6.02214076e23; var resultDiv = document.getElementById('particleResult'); if (isNaN(particles) || particles <= 0) { resultDiv.style.display = 'block'; resultDiv.style.backgroundColor = '#fdeded'; resultDiv.style.color = '#c0392b'; resultDiv.innerHTML = 'Please enter a valid number of particles.'; return; } var moles = particles / avogadro; resultDiv.style.display = 'block'; resultDiv.style.backgroundColor = '#eafaf1'; resultDiv.style.color = '#27ae60'; if (moles < 0.0001) { resultDiv.innerHTML = 'Result: ' + moles.toExponential(4) + ' moles'; } else { resultDiv.innerHTML = 'Result: ' + moles.toFixed(4) + ' moles'; } }