Question

1. choose the product that best provide evidence of chemical change with the equation.

\ce{na_{2}s (aq) + 2hcl (aq) -> 2nacl (aq) + h_{2}s (g)}
this reaction produced ____.

• water
• precipitate
• gas

1. choose the product that best provide evidence of chemical change with the equation.

\ce{2na_{3}po_{4} (aq) + 3cacl_{2} (aq) -> 6nacl (aq) + ca_{3}(po_{4})_{2} \downarrow}
this reaction produced ____.

• water
• gas
• precipitate

Explanation:

Question 12

Step1: Analyze the reaction products

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

Step2: Identify the evidence of chemical change

Among the options (water, precipitate, gas), $\ce{H_{2}S}$ is a gas (indicated by the $(g)$ state symbol). So the product that shows chemical change is gas.

Step1: Analyze the reaction products

The reaction is $\ce{2Na_{3}PO_{4}(aq) + 3CaCl_{2}(aq) -> 6NaCl(aq) + Ca_{3}(PO_{4})_{2}\downarrow}$. The products are $\ce{NaCl(aq)}$ and $\ce{Ca_{3}(PO_{4})_{2}\downarrow}$.

Step2: Identify the evidence of chemical change

The $\downarrow$ symbol next to $\ce{Ca_{3}(PO_{4})_{2}}$ indicates a precipitate (a solid formed from aqueous solutions). Among the options (water, gas, precipitate), the product showing chemical change is a precipitate.

Answer:

gas (the option with "gas" as text)

Question 13