Molar Mass of Potassium alum
KAl(SO4)2·12H2O — 474.372 g/mol, worked out element by element.
Molar mass of Potassium alum, KAl(SO₄)₂·₁₂H₂O
474.372 g/mol
Molecular weight 474.372 · 48 atoms per formula unit · includes 12 waters of crystallisation
Also known as: kal(so4)2.12h2o, alum, potash alum.
Twelve waters of crystallisation, which makes it the hardest hydrate on most worksheets.
How 474.372 g/mol is worked out
| Element | Atoms | Atomic mass | Mass | % of total |
|---|---|---|---|---|
| Oxygen | 20 | 15.999 | 319.980 | 67.45% |
| Sulfur | 2 | 32.06 | 64.120 | 13.52% |
| Potassium | 1 | 39.098 | 39.098 | 8.24% |
| Aluminum | 1 | 26.982 | 26.982 | 5.69% |
| Hydrogen | 24 | 1.008 | 24.192 | 5.10% |
| Total | 48 | 474.372 | 100% |
M = 20 × 15.999 + 2 × 32.060 + 1 × 39.098 + 1 × 26.982 + 24 × 1.008 = 474.372 g/mol
Grams to moles for Potassium alum
| Mass | Moles | Formula units |
|---|---|---|
| 1 g | 0.0021 mol | 1.269 × 10^21 |
| 10 g | 0.0211 mol | 1.269 × 10^22 |
| 25 g | 0.0527 mol | 3.174 × 10^22 |
| 50 g | 0.1054 mol | 6.347 × 10^22 |
| 100 g | 0.2108 mol | 1.269 × 10^23 |
| 250 g | 0.5270 mol | 3.174 × 10^23 |
| 474.372 g | 1 mol | 6.022 × 10^23 |
For any other amount, use the molar mass calculator, or the molarity calculator to make up a solution of a given concentration.
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Frequently Asked Questions
What is the molar mass of Potassium alum?
The molar mass of Potassium alum (KAl(SO4)2·12H2O) is 474.372 g/mol. That is the sum of the standard atomic weights of all 48 atoms in one formula unit: 20 × 15.999 + 2 × 32.060 + 1 × 39.098 + 1 × 26.982 + 24 × 1.008 = 474.372.
What is the molecular weight of Potassium alum?
474.372 — the same number as the molar mass, but as a dimensionless ratio rather than in g/mol. The two terms describe the same arithmetic, so a molecular weight of 474.37 and a molar mass of 474.37 g/mol are the same answer.
How many moles are in 100 g of Potassium alum?
100 ÷ 474.372 = 0.2108 mol. To convert any mass to moles, divide by the molar mass; to go the other way, multiply.
What is the percent composition of Potassium alum?
By mass, Potassium alum is 67.45% oxygen, 13.52% sulfur, 8.24% potassium, 5.69% aluminum, 5.10% hydrogen. Each element's share is its total mass in the formula divided by 474.372.
How many atoms are in one formula unit of Potassium alum?
48: 20 oxygen, 2 sulfur, 1 potassium, 1 aluminum, 24 hydrogen. One mole contains 6.02214076 × 10²³ formula units, so a mole of Potassium alum contains 48 × 6.022 × 10²³ atoms in total.