sci_chem
The Mole
Chapter summary, hard words and model exam answers for Hindi.
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Chemistry · CBSE 10 · ICSE 10 · GCSE (AQA, Edexcel, OCR)
Summary
A single atom weighs about 10^-23 g, impossible to weigh alone. The mole lets us weigh out a known number of atoms in grams.
It works for atoms, molecules, ions or formula units. 1 mole of Na has the same count as 1 mole of water.
Na is 23, so 1 mole of Na weighs 23 g. For water, Mr = (2×1) + 16 = 18, so 1 mole weighs 18 g.
44 g of CO2 (Mr = 44) is 1 mole, which is 6.02 × 10^23 molecules. These two steps run all of quantitative chemistry.
Hard words & meanings
| mole | the amount of a substance that contains 6.02 × 10^23 particles |
| Avogadro's number | the number of particles in one mole, 6.02 × 10^23, symbol N_A |
| molar mass | the mass of one mole of a substance, in grams per mole |
| relative atomic mass (Ar) | the average mass of an atom compared with carbon-12 |
| relative molecular mass (Mr) | the sum of the relative atomic masses of all atoms in a molecule |
| empirical formula | the simplest whole-number ratio of atoms in a compound |
| molecular formula | the actual number of each kind of atom in one molecule |
| formula unit | the simplest ratio of ions in an ionic compound, such as NaCl |
Model exam answers, grammar & audio
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