Question

which of the following chemical equations is balanced?

a) \\(\text{nh}_3 + \text{h}_2\text{o} \
ightarrow 2\text{nh}_4\text{oh}\\)

b) \\(2\text{na} + \text{s} \
ightarrow 2\text{nas}\\)

c) \\(\text{koh} + \text{h}_2\text{so}_4 \
ightarrow \text{khso}_4 + \text{h}_2\text{o}\\)

d) \\(2\text{nacl} + \text{h}_2\text{so}_4 \
ightarrow \text{hcl} + \text{naso}_4\\)

Explanation:

Analyze the definition of a balanced equation

A balanced chemical equation must have the same number of atoms of each element on both the reactant (left) and product (right) sides, demonstrating the conservation of mass.

Evaluate option A

Reactants: \(\text{NH}_3 + \text{H}_2\text{O}\)

• \(\text{N} = 1\)
• \(\text{H} = 3 + 2 = 5\)
• \(\text{O} = 1\)

Products: \(2\text{NH}_4\text{OH}\)

• \(\text{N} = 2\)
• \(\text{H} = 2 \times (4 + 1) = 10\)
• \(\text{O} = 2\)

The atoms are not equal. Option A is unbalanced.

Evaluate option B

Reactants: \(2\text{Na} + \text{S}\)

• \(\text{Na} = 2\)
• \(\text{S} = 1\)

Products: \(2\text{NaS}\)

• \(\text{Na} = 2\)
• \(\text{S} = 2\)

The sulfur atoms are not equal. Option B is unbalanced.

Evaluate option C

Using the Chemical Reactions knowledge point, we count the atoms on both sides:

Reactants: \(\text{KOH} + \text{H}_2\text{SO}_4\)

• \(\text{K} = 1\)
• \(\text{O} = 1 + 4 = 5\)
• \(\text{H} = 1 + 2 = 3\)
• \(\text{S} = 1\)

Products: \(\text{KHSO}_4 + \text{H}_2\text{O}\)

• \(\text{K} = 1\)
• \(\text{H} = 1 + 2 = 3\)
• \(\text{S} = 1\)
• \(\text{O} = 4 + 1 = 5\)

All atom counts match perfectly. Option C is balanced.

Evaluate option D

Reactants: \(2\text{NaCl} + \text{H}_2\text{SO}_4\)

• \(\text{Na} = 2\)
• \(\text{Cl} = 2\)
• \(\text{H} = 2\)
• \(\text{S} = 1\)
• \(\text{O} = 4\)

Products: \(\text{HCl} + \text{NaSO}_4\)

• \(\text{H} = 1\)
• \(\text{Cl} = 1\)
• \(\text{Na} = 1\)
• \(\text{S} = 1\)
• \(\text{O} = 4\)

The atoms are not equal. Option D is unbalanced.

Answer:

• A) \(\text{NH}_3 + \text{H}_2\text{O}

ightarrow 2\text{NH}_4\text{OH}\)

• B) \(2\text{Na} + \text{S}

ightarrow 2\text{NaS}\)

• **C) \(\text{KOH} + \text{H}_2\text{SO}_4

ightarrow \text{KHSO}_4 + \text{H}_2\text{O}\) (Correct answer)**

• D) \(2\text{NaCl} + \text{H}_2\text{SO}_4

ightarrow \text{HCl} + \text{NaSO}_4\)