Question

Hydrogen gas and aqueous zinc chloride are produced by the reaction of aqueous hydrochloric acid and solid zinc . Write a balanced chemical equation for this reaction.

Answer 1

1. Write out all the ions/elements and indicate whether they are reactants or products.

Reactants:

Aqueous Hydrochloric Acid: HCl (H has a charge of +1 and Cl has a charge of 1-, so when an ionic bond forms they will form HCl).

Solid Zinc: Zn (since it is a solid zinc with no other forms of elements, the zinc is pure).

Products:

Hydrogen gas: H2 (it has to be H2 because Hydrogen is a diatomic element, and when by itself during reactions, will be H2 instead of H).

Aqueous Zinc Chloride: ZnCl2 (Zn has a charge of 2+ and Cl has a charge of 1-, so through an ionic bond, they will form ZnCl2).

2. Using this information, you can then write out the unbalanced equation.

HCl + Zn -> H2 + ZnCl2

3. Next, indicate their states of matter and any aqueous solutions.

HCl (aq) + Zn (s) -> H2 (g) + ZnCl2 (aq)

4. Try different numbers until you get the same numbers of H, Cl, and Zn on both sides.

2 HCl (aq) + Zn (s) -> H2 (g) + ZnCl2 (aq)

As you can see, the equation contains 2 Hydrogen atoms on both sides, 2 Chloride atoms on both sides, and 1 Zinc atom on both sides. The equation is chemically balanced.