Grams to moles
0.500 molin 22 g of CO₂
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.
44.01g/mol
CO₂
- C× 127.29%
- O× 272.71%
- C1 × 12.0112.01
- O2 × 16.0032.00
- Total44.01 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.
0.500 mol of CO₂ = 3.011 × 10²³ molecules
At 1 atm (older value): 11.20 L
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.
%
%
%
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.
N₂ + 3 H₂ → 2 NH₃
- N₂1784 mol ÷ 1 = 17843.67 kg left over
- H₂4960 mol ÷ 3 = 1653Limiting
Formed
- NH₃3307 mol56.3 kg
The NCERT way
moles = mass (g) ÷ molar mass (g/mol)
How many moles are there in 22 g of carbon dioxide, CO₂?
- Molar mass of CO₂ = 12.01 + 2 × 16.00 = 44.01 g/mol.
- Moles = mass ÷ molar mass = 22 ÷ 44.01 = 0.500 mol.
- 22 g of CO₂ is 0.500 mol.
Grams to moles: quick answers
How do you convert grams to moles?
Divide the mass in grams by the molar mass in g/mol. The answer is the amount of substance in moles.
How many moles are in 22 g of CO₂?
The molar mass of CO₂ is 44.01 g/mol, so 22 g is 22 ÷ 44.01 = 0.500 mol.
Why do we use moles instead of grams?
Equations count particles, not grams. A mole always holds the same number of particles, 6.022 × 10²³, so moles let you read an equation as amounts you can weigh.