The molar mass of water is M = 18 * 10 ^ -3 kg / mol. How many molecules are there in 10 kg of water?
| February 8, 2021 | education
M = 18 * 10 ^ -3 kg / mol.
m = 10 kg.
NA = 6 * 10 ^ 23 mol − 1.
N -?
The number of water molecules N is expressed by the formula: N = v * Na, where v is the amount of substance, Na is Avogadro’s number. Avogadro’s number NA shows how many molecules of a substance are in 1 mole of a substance: NA = 6 * 10 ^ 23 mol − 1.
The amount of substance v is found by the formula: v = m / M, where m is the mass of water, M is the molar mass of water.
The number of water molecules N will be determined by the formula: N = NA * m / M.
N = 6 * 10 ^ 23 mol − 1 * 10 kg / 18 * 10 ^ -3 kg / mol = 3.33 * 10 ^ 20.
Answer: 10 kg of water contains N = 3.33 * 10 ^ 20 water molecules.
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