Question

1. choose the best answer.

when the following equation is balanced, what is the coefficient for libr?
—— f₂(g) + —— libr(aq) → —— lif(s) + —— br₂(l)
1
2
3
4

1. choose the best answer.

the reaction between solid magnesium (mg) and atmospheric (gaseous) oxygen (o₂) is used in fireworks. this reaction creates the product magnesium oxide (mgo).
which equation shows the correct balanced equation for this reaction?
mg(g) + o(g) → mgo(s)
2mg(g) + o₂(l) → 2mgo(s)
2mg(g) + o₂(g) → 2mgo(s)
mg(g) + o₂(g) → 2mgo₂(s)

Explanation:

Step1: Balance Br atoms

Count Br on right: 2 (in $\text{Br}_2$). So $\text{LiBr}$ needs coefficient 2 to get 2 Br on left.

Step2: Balance Li atoms

With $\text{LiBr}$ coefficient 2, Li on left is 2. So $\text{LiF}$ needs coefficient 2 to match Li on right.

Step3: Balance F atoms

$\text{LiF}$ has coefficient 2, so F on right is 2. $\text{F}_2$ has 2 F, so its coefficient is 1. Balanced equation:

$$1\text{F}_2(g) + 2\text{LiBr}(aq) ightarrow 2\text{LiF}(s) + 1\text{Br}_2(l)$$

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Step1: Identify reactant states

Mg is solid ($s$), atmospheric $\text{O}_2$ is gas ($g$).

Step2: Balance Mg and O atoms

Unbalanced: $\text{Mg}(s) + \text{O}_2(g)
ightarrow \text{MgO}(s)$. Add 2 to Mg and MgO:

$$2\text{Mg}(s) + \text{O}_2(g) ightarrow 2\text{MgO}(s)$$

Answer:

1. 2
2. $2\text{Mg}(s) + \text{O}_2(g)

ightarrow 2\text{MgO}(s)$