The mass of one mole of a substance is equal to the mass of the molecule, expressed in atomic mass units, multiplied by 0.001 kg. For copper sulfate CuSO4, the relative atomic mass is:
Cu – 63.54 a. eat.;
S – 32.066 a. eat.;
O4 – 16 * 4 = 64 amu. eat.;
Total: 159.606 AU eat.
Weight of one mole: 159.606 * 0.001 kg = 0.160 kg.
The amount of substance in two kilograms of vitriol:
n = m / M = 2 kg / 0.1596 kg = 12.53 mol.
The number of molecules is equal to the number of moles of the substance multiplied by the Avogadro number NA:
N = n * NA = 12.53 mol * 6.022 * 10²³ mol⁻¹ = 7.55 * 10²⁴.
Answer: Approximately 7.55 * 10²⁴ molecules.
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