Question

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Explanation:

Step1: Balance HgO decomposition

Balance O: 2 O on left, so $1\ O_2$ (2 O total).

$$2\text{HgO} ightarrow 2\text{Hg} + 1\text{O}_2$$

Step2: Balance Ca + H₂O reaction

Balance Ca: 1 Ca on left, so $1\ \text{Ca(OH)}_2$. Balance O: 2 O from $2\ \text{H}_2\text{O}$ matches 2 O in $\text{Ca(OH)}_2$.

$$1\text{Ca} + 2\text{H}_2\text{O} ightarrow 1\text{Ca(OH)}_2 + 1\text{H}_2$$

Step3: Balance C + O₂ reaction

Balance O: 2 O in $2\ \text{CO}$, so $1\ \text{O}_2$.

$$2\text{C} + 1\text{O}_2 ightarrow 2\text{CO}$$

Step4: Balance Na₂O₂ + H₂SO₄

Balance Na: 2 Na in $\text{Na}_2\text{O}_2$, so $1\ \text{Na}_2\text{SO}_4$. Balance S: 1 S in $\text{H}_2\text{SO}_4$ matches 1 S in $\text{Na}_2\text{SO}_4$. Balance O/H: 2 O from $\text{Na}_2\text{O}_2$ + 4 O from $\text{H}_2\text{SO}_4$ = 4 O in $\text{Na}_2\text{SO}_4$ + 2 O in $\text{H}_2\text{O}_2$; 2 H from $\text{H}_2\text{SO}_4$ matches 2 H in $\text{H}_2\text{O}_2$.

$$1\text{Na}_2\text{O}_2 + 1\text{H}_2\text{SO}_4 ightarrow 1\text{Na}_2\text{SO}_4 + 1\text{H}_2\text{O}_2$$

Step5: Balance HCl + Mg reaction

Balance Mg: 1 Mg on left, so $1\ \text{MgCl}_2$. Balance H/Cl: 2 Cl in $\text{MgCl}_2$ needs $2\ \text{HCl}$, which gives 2 H for $1\ \text{H}_2$.

$$2\text{HCl} + 1\text{Mg} ightarrow 1\text{MgCl}_2 + 1\text{H}_2$$

Step6: Verify Al + O₂ reaction

Given coefficients are balanced: 4 Al (4 Al in $2\text{Al}_2\text{O}_3$), 6 O (3 $\text{O}_2$ = 6 O in $2\text{Al}_2\text{O}_3$).

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

Answer:

1. $2\text{HgO}

ightarrow 2\text{Hg} + \boldsymbol{1}\text{O}_2$

1. $\boldsymbol{1}\text{Ca} + 2\text{H}_2\text{O}

ightarrow \boldsymbol{1}\text{Ca(OH)}_2 + 2\text{H}_2$

1. $2\text{C} + \boldsymbol{1}\text{O}_2

ightarrow 2\text{CO}$

1. $\boldsymbol{1}\text{Na}_2\text{O}_2 + \boldsymbol{1}\text{H}_2\text{SO}_4

ightarrow \boldsymbol{1}\text{Na}_2\text{SO}_4 + \boldsymbol{1}\text{H}_2\text{O}_2$

1. $2\text{HCl} + \boldsymbol{1}\text{Mg}

ightarrow \boldsymbol{1}\text{MgCl}_2 + \boldsymbol{1}\text{H}_2$

1. $4\text{Al}(s) + 3\text{O}_2(g)

ightarrow 2\text{Al}_2\text{O}_3$ (already balanced)