Calculate the amount of 140 g of oxygen.

The amount of a substance means the amount of moles of a given substance. The number of moles is calculated as the ratio of the mass of a sample of a substance to its molar mass. Oxygen at n.u. a gas consisting of two atoms, therefore its molar mass is 16 * 2 = 32 g / mol.

We find the amount of oxygen substance:

n = 140/32 = 4.375 mol

Answer: 4.375 moles of oxygen in 140 g.

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