Student Question

In my chemistry book it says that the mass of one molecule of `H_2SO_4` is `1.63*10^(-22) g.`  Could you explain how they get this?

Expert Answers

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Hello! Yes we can:)

All atoms of each type have their specific masses. They are known, particularly in grams per mole. By the definition, one mole of any set of particles contains fixed number of particles, called Avogadro number. It is denoted `N_A` and is equal to about `6 * 10^(23).`

The mass of one mole of hydrogen `H` is about `1 (g)/(mol),` the mass of one mole of sulfur `S` is about `32 (g)/(mol)` and the mass of one mole of oxygen `O` is about `16 (g)/(mol).`

Therefore the mass of one mole of sulfuric acid `H_2SO_4` is about `2*1 + 32 + 4*16 = 98 (g)/(mol).` Finally, one molecule of sulfuric acid has the mass about `98/N_A approx 98/(6*10^(23)) approx 16.3*10^(-23)=1.63*10^(-22) (g).` So your book says the truth.

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