Question

How many grams of hydrochloric acid are required to react completely with 4.30 grams of zinc? I got 4.80g HCl for the answer but do not know how to do part 2 which is, How many molecules of a gas will be produced?

Thanks.

Answer 1

How did you do the HCl part? Something like this?
mols Zn = g/molar mass = 4.30/65.37 = 0.06578
Then convert mols Zn to mols HCl using the coefficients in the balanced equation.
mols HCl = 0.06578 x(2 mols HCl/1 mol Zn) = 0.06578 x 2 = 0.1316
Then convert mols HCl to grams. mols x molar mass = g = 0.1316 x 36.5 = 4.80 g HCl required.

Now we do the same thing for mols H2.
mols Zn = 4.30/65.37 = 0.06578
Convert to mols H2 gas.
0.06578 mols Zn x (1 mol H2/1 mol Zn) = 0.06578 mols H2.
How many molecules. We know there are 6.02 x 10^23 molecules in a mol. Therefore,
molecules = 0.06578 mols H2 x (6.02 x 10^23 molecules/1 mol) = ??
I hope this helps.
Check my work carefully.