chemistry help please

Question

if 0.375 moles of hydrogen are made in the reaction of zinc with hydrochloric acid, how many moles of zinc were used?

Answer 1

Hello, Molly,

We need to have a balanced reaction. Zn reacts with HCl to produce hydrogen is all we are given.

Zn + HCL = H₂ + ?

The zinc replaces the hydrogen on the HCl. But zinc has an oxidation state of 2, so it will have a charge of +2. Since chloride ions have a charge of -1, we'll need two chlorines per zinc, to produce ZnCl₂.

We can add this compound to our equation:

Zn + HCl = H₂ + ZnCl.

Now we balance it. Note that we need two H atoms (H₂) since hydrogen is diatomic. The HCl only provides 1, so we need to double it:

Zn + 2HCl = H₂ + ZnCl₂

The equation is now balanced, and it tells us that we 1 mole of Zn for every 1 mole of H₂ produced. Since we produced 0.375 moles of H₂, we consumed the same number of moles of Zn (0.375 moles Zn).

Bob