Chemistry

Mole calculator

Type a formula. Get every amount.

Molar mass

Molar mass. The mass of one mole in grams: add the atomic mass of every atom in the formula. Masses. Standard atomic masses to two decimals, hydrogen 1.008, every element to uranium. Typing. Ca(OH)2, (NH4)2SO4, CuSO4.5H2O and K4[Fe(CN)6] all work.

Formula

18.02g/mol

H₂O

H× 211.19%
O× 188.81%

H2 × 1.0082.016
O1 × 16.0016.00
Total18.02 g/mol

Grams, moles, particles

Type any one. The other three fill in. Moles. From grams, particles or litres they are rounded to 3 significant figures first, as in a worked answer. 1 mol = 6.022 × 10²³ particles = 22.7 L of gas at STP (1 bar); 22.4 L at 1 atm.

Mass g Moles mol Particles molecules Gas at STP L

0.5 mol of H₂O = 3.011 × 10²³ molecules

At 1 atm (older value): 11.20 L

In mL of solution: 2.00 M

Empirical formula

1. Take 100 g, so each percentage is grams. 2. Divide by the atomic mass to get moles, then by the smallest. 3. Multiply by 2, 3 or 4 if a ratio ends in .5, .33 or .25. Molecular formula. Add the molar mass: n = molar mass ÷ empirical formula mass.

%

Molar mass g/mol

Empirical formulaCH₂Cl49.48 g/mol

Molecular formulaC₂H₄Cl₂n = 98.96 ÷ 49.48 = 2

Element	g in 100 g	÷ mass	÷ least	Whole
H	4.07	4.038	2.00	2
C	24.27	2.021	1.00	1
Cl	71.65	2.021	1.00	1

Limiting reagent

1. The equation is balanced for you. 2. Each mass becomes moles, divided by its coefficient. 3. The smallest runs out first: it is the limiting reagent and sets how much product forms. Leave a mass empty if that reactant is in excess.

Equation

N₂kgH₂kg

N₂ + 3 H₂ → 2 NH₃

N₂1784 mol ÷ 1 = 17843.67 kg left over
H₂4960 mol ÷ 3 = 1653Limiting

Formed

NH₃3307 mol56.3 kg

Worked examples

The mole, step by step

Same chapter: organic conversions, name reactions, electron configuration, oxidation numbers and redox, bonding and shapes, balance equations.

Questions students ask

Moles and molar mass

What is a mole?

A mole is an amount of substance holding 6.022 × 10²³ particles, the Avogadro constant. The mass of one mole in grams is the molar mass, so 1 mol of water is 18.02 g.

How do I find the molar mass of a compound?

Multiply the atomic mass of each element by the number of its atoms in the formula and add them up. For H₂SO₄: 2 × 1.008 + 32.06 + 4 × 16.00 = 98.08 g/mol.

Which atomic masses does the calculator use?

The standard atomic masses to two decimal places, as in the NCERT books, with hydrogen as 1.008. The masses of every element up to uranium are included.

What volume does one mole of gas fill at STP?

22.7 L at 273.15 K and 1 bar, the value NCERT uses. Older books use 22.4 L, which is at 1 atm.

Why are moles rounded to three significant figures?

When you start from grams, particles or litres, the moles are rounded to three significant figures first, the way a worked answer is written, and the other amounts are worked out from that.