Question

modeling and practice
h₂ + o₂ --> h₂o
zn + hcl --> zncl₂ + h₂
c₃h₈ + o₂ --> co₂ + h₂o
kno₃ --> kno₂ + o₂

Explanation:

Step1: Balance H₂ + O₂ → H₂O

First balance O: add 2 to H₂O, then balance H: add 2 to H₂.

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

Step2: Balance Zn + HCl → ZnCl₂ + H₂

Balance Cl: add 2 to HCl (H is automatically balanced).

$$\text{Zn} + 2\text{HCl} ightarrow \text{ZnCl}_2 + \text{H}_2$$

Step3: Balance C₃H₈ + O₂ → CO₂ + H₂O

Balance C: add 3 to CO₂; balance H: add 4 to H₂O; balance O: add 5 to O₂.

$$\text{C}_3\text{H}_8 + 5\text{O}_2 ightarrow 3\text{CO}_2 + 4\text{H}_2\text{O}$$

Step4: Balance KNO₃ → KNO₂ + O₂

Balance O: add 2 to KNO₃, KNO₂; O is balanced.

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

Answer:

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

ightarrow 2\text{H}_2\text{O}$

1. $\text{Zn} + 2\text{HCl}

ightarrow \text{ZnCl}_2 + \text{H}_2$

1. $\text{C}_3\text{H}_8 + 5\text{O}_2

ightarrow 3\text{CO}_2 + 4\text{H}_2\text{O}$

1. $2\text{KNO}_3

ightarrow 2\text{KNO}_2 + \text{O}_2$