Question

which represents a balanced chemical equation?\
$\ce{co_{2} + 2h_{2}o -> 2ch_{4} + 2o_{2}}$\
$\ce{ch_{4} + 2o_{2} -> co_{2} + 2h_{2}o}$\
$\ce{co_{2} + h_{2}o -> ch_{4} + o_{2}}$\
$\ce{ch_{4} + o_{2} -> co_{2} + h_{2}o}$

Explanation:

Step1: Analyze Option 1 ($\boldsymbol{CO_2 + 2H_2O

ightarrow 2CH_4 + 2O_2}$)
Count atoms: C: 1 vs 2, H: 4 vs 8, O: 4 vs 4. Not balanced.

Step2: Analyze Option 2 ($\boldsymbol{CH_4 + 2O_2

ightarrow CO_2 + 2H_2O}$)
Count atoms: C: 1 = 1, H: 4 = 4 (2×2), O: 4 (2×2) = 2 + 2 (2×1). Balanced.

Step3: Analyze Option 3 ($\boldsymbol{CO_2 + H_2O

ightarrow CH_4 + O_2}$)
Count atoms: C: 1 = 1, H: 2 vs 4, O: 3 vs 2. Not balanced.

Step4: Analyze Option 4 ($\boldsymbol{CH_4 + O_2

ightarrow CO_2 + H_2O}$)
Count atoms: C: 1 = 1, H: 4 vs 2, O: 2 vs 3. Not balanced.

Answer:

B. $\boldsymbol{CH_4 + 2O_2
ightarrow CO_2 + 2H_2O}$