Question

1. choose the best answer.

look at the products of this equation. what is formed that provides evidence of a chemical change?
na₂s(aq) + 2hcl(aq) → 2nacl(aq) + h₂s(g)
○ gas
○ water
○ precipitate

1. choose all that apply.

look at the products of this equation. what two are formed that provide evidence of a chemical change?
2naoh(aq) + h₂co₃(aq) → na₂co₃(s) + 2h₂o(l)
□ precipitate
□ gas
□ water

Explanation:

Question 3

Step1: Analyze the products

The reaction is $\ce{Na_{2}S(aq) + 2HCl(aq) -> 2NaCl(aq) + H_{2}S(g)}$. The products are $\ce{NaCl(aq)}$ (aqueous) and $\ce{H_{2}S(g)}$ (gas).

Step2: Evaluate the options

• "gas": $\ce{H_{2}S}$ is a gas, so this is evidence of a chemical change.
• "water": No water is a product here.
• "precipitate": Both products are aqueous or gas, no precipitate.

Step1: Analyze the products

The reaction is $\ce{2NaOH(aq) + H_{2}CO_{3}(aq) -> Na_{2}CO_{3}(s) + 2H_{2}O(l)}$. The products are $\ce{Na_{2}CO_{3}(s)}$ (solid, a precipitate) and $\ce{H_{2}O(l)}$ (liquid, water).

Step2: Evaluate the options

• "precipitate": $\ce{Na_{2}CO_{3}(s)}$ is a solid precipitate, so this is evidence.
• "gas": No gas is a product.
• "water": $\ce{H_{2}O(l)}$ is a product, so this is evidence.

Answer:

A. gas

Question 4