Question

2.56 grams of zinc react with excess phosphoric acid to produce how many molecules of hydrogen gas?

Answer 1

Zn + 2HCl ==> ZnCl2 + H2

mols Zn = grams/molar mass = ?
Using the coefficients in the balanced equation, convert mols Zn to mols H2.
Then mols H2 gas x 6.02E23 molecules/mol H2 = ? # molecules H2 gas.