Use the electron-transfer method to balance this equation:

Zn (s) + HCl (aq) → ZnCl2 (aq) + H2 (g)

a. 2Zn (s) + HCl (aq) → ZnCl2 (aq) + H2 (g)

b. Zn (s) + 2HCl (aq) →ZnCl2 (aq) + H2 (g)

c. Zn (s) + HCl (aq) →ZnCl2 (aq) + H2 (g)

d. 2Zn (s) + 4HCl (aq) → 2ZnCl2 (aq) + 2H2 (g)

e. 3Zn (s) + 3HCl (aq) →3ZnCl2 (aq) + 3H2 (g)

The answer to your question is the letter d.

Explanation:

Data

Zn + HCl ⇒ ZnCl₂ + H₂

- Calculate the Oxidation number of reactants and products

Zn⁰ + H⁺¹Cl⁻¹ ⇒ Zn⁺²Cl₂⁻¹ + H₂⁰

- Determine which elements changed their oxidation numbers

Zn⁰ ⇒ Zn⁺² Zn lost 2e⁻

2H⁺¹ ⇒ H₂⁰ H won 2 e⁻

-Interchange the electrons lost and won

2 (Zn⁰ ⇒ Zn⁺²)

2 (2H⁺¹ ⇒ H₂⁰)

-Simplify

2Zn⁰ ⇒ 2Zn⁺²

4H⁺¹ ⇒ 2H₂⁰

-Substitute the coefficient in the equation

2Zn + 4HCl ⇒ 2ZnCl₂ + 2H₂

Reactant Element Product

2 Zn 2

4 H 4

4 Cl 4

- Now the reaction is balanced