Question

1. __koh → k₂o + __h₂o
2. __mg + h₂o → mg(oh)₂ + __h₂
3. __k₃po₄ + hcl → kcl + __h₃po₄
4. __na + hno₃ → nano₃ + __h₂
5. __s + o₂ → __so₃
6. __ca(clo₃)₂ → cacl₂ + __o₂
7. __ki + pb(no₃)₂ → kno₃ + __pbi₂
8. __fe₂o₃ + c → co + __fe
9. __hno₃ + na₂co₃ → nano₃ + __h₂co₃

Explanation:

Step1: Balance K atoms

$2\text{KOH}
ightarrow \text{K}_2\text{O} + \text{H}_2\text{O}$

Step2: Verify all atoms

Count K: 2 on left, 2 on right; O: 2 on left, 2 on right; H: 2 on left, 2 on right. Balanced.

Step1: Balance Mg, then O/H

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

Step2: Verify all atoms

Mg:1=1; H:4=2+2; O:2=2. Balanced.

Step1: Balance K, then Cl/P

$\text{K}_3\text{PO}_4 + 3\text{HCl}
ightarrow 3\text{KCl} + \text{H}_3\text{PO}_4$

Step2: Verify all atoms

K:3=3; P:1=1; Cl:3=3; H:3=3; O:4=4. Balanced.

Step1: Balance Na, then H

$2\text{Na} + 2\text{HNO}_3
ightarrow 2\text{NaNO}_3 + \text{H}_2$

Step2: Verify all atoms

Na:2=2; N:2=2; O:6=6; H:2=2. Balanced.

Step1: Balance O, then S

$2\text{S} + 3\text{O}_2
ightarrow 2\text{SO}_3$

Step2: Verify all atoms

S:2=2; O:6=6. Balanced.

Step1: Balance O, then check others

$\text{Ca(ClO}_3\text{)}_2
ightarrow \text{CaCl}_2 + 3\text{O}_2$

Step2: Verify all atoms

Ca:1=1; Cl:2=2; O:6=6. Balanced.

Step1: Balance I, then K/N/Pb

$2\text{KI} + \text{Pb(NO}_3\text{)}_2
ightarrow 2\text{KNO}_3 + \text{PbI}_2$

Step2: Verify all atoms

K:2=2; I:2=2; Pb:1=1; N:2=2; O:6=6. Balanced.

Step1: Balance Fe, then C/O

$\text{Fe}_2\text{O}_3 + 3\text{C}
ightarrow 3\text{CO} + 2\text{Fe}$

Step2: Verify all atoms

Fe:2=2; O:3=3; C:3=3. Balanced.

Step1: Balance Na/N, then check others

$2\text{HNO}_3 + \text{Na}_2\text{CO}_3
ightarrow 2\text{NaNO}_3 + \text{H}_2\text{CO}_3$

Step2: Verify all atoms

H:2=2; N:2=2; O:9=9; Na:2=2; C:1=1. Balanced.

Answer:

1. $2\text{KOH}

ightarrow \text{K}_2\text{O} + \text{H}_2\text{O}$

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

ightarrow \text{Mg(OH)}_2 + \text{H}_2$

1. $\text{K}_3\text{PO}_4 + 3\text{HCl}

ightarrow 3\text{KCl} + \text{H}_3\text{PO}_4$

1. $2\text{Na} + 2\text{HNO}_3

ightarrow 2\text{NaNO}_3 + \text{H}_2$

1. $2\text{S} + 3\text{O}_2

ightarrow 2\text{SO}_3$

1. $\text{Ca(ClO}_3\text{)}_2

ightarrow \text{CaCl}_2 + 3\text{O}_2$

1. $2\text{KI} + \text{Pb(NO}_3\text{)}_2

ightarrow 2\text{KNO}_3 + \text{PbI}_2$

1. $\text{Fe}_2\text{O}_3 + 3\text{C}

ightarrow 3\text{CO} + 2\text{Fe}$

1. $2\text{HNO}_3 + \text{Na}_2\text{CO}_3

ightarrow 2\text{NaNO}_3 + \text{H}_2\text{CO}_3$