Question

1. choose the best answer.

the following shows chemical equations that students have recorded in their lab journals after performing several experiments.

experiment	equation

| experiment 1 | $4fe(s) + 3o_2(g) \
ightarrow 2fe_2o_3(s)$ |
| experiment 2 | $cu(s) + agno_3(aq) \
ightarrow cuno_3(aq) + ag(s)$ |
| experiment 3 | $pb(no_3)_2(aq) + 2ki(aq) \
ightarrow pbi_2(s) + 2kno_3(aq)$ |

which of these is a solid?

• $agno_3$
• $pb(no_3)_2$
• $pbi_2$ (selected)
• $kno_3$

1. choose the best answer.

what is the coefficient of $o_2$ in experiment 1?

Explanation:

Step1: Identify solid from options

Check solubility states:

• $\text{AgNO}_3$: soluble (aqueous, $aq$)
• $\text{Pb(NO}_3\text{)}_2$: soluble (aqueous, $aq$)
• $\text{PbI}_2$: insoluble (solid, $s$, from Experiment 3 equation)
• $\text{KNO}_3$: soluble (aqueous, $aq$)

Step2: Locate $\text{O}_2$ coefficient

Look at Experiment 1 equation:

$$4\text{Fe}(s) + 3\text{O}_2(g) ightarrow 2\text{Fe}_2\text{O}_3(s)$$

The coefficient of $\text{O}_2$ is 3.

Answer:

1. $\text{PbI}_2$
2. 3