To determine which of the given chemical equations is balanced, let's analyze each one:
A) \( \text{NH}_3 + \text{H}_2\text{O} \rightarrow 2\text{NH}_4\text{OH} \)
- Left side: 1 nitrogen (N), 3 hydrogens (H) from NH₃, and 2 from H₂O, totaling 5 H; 1 oxygen (O).
- Right side: 2 nitrogens (N), 8 hydrogens (H), and 2 oxygens (O).
- Not balanced.
B) \( 2\text{NaCl} + \text{H}_2\text{SO}_4 \rightarrow \text{HCl} + \text{Na}_2\text{SO}_4 \)
- Left side: 2 sodium (Na), 2 chlorine (Cl), 1 sulfur (S), 4 oxygens (O), and 2 hydrogens (H).
- Right side: 2 sodium (Na), 1 sulfur (S), 4 oxygens (O), and 1 chlorine (Cl) and 1 hydrogen, which results in only 1 H.
- Not balanced.
C) \( 2\text{Na} + \text{S} \rightarrow 2\text{NaS} \)
- Left side: 2 sodium (Na), 1 sulfur (S).
- Right side: 2 sodium (Na), 2 sulfur (S) (because NaS has 1 sulfur each for two units).
- Not balanced.
D) \( \text{KOH} + \text{H}_2\text{SO}_4 \rightarrow \text{KHSO}_4 + \text{H}_2\text{O} \)
- Left side: 1 potassium (K), 1 oxygen (O) from KOH, 2 hydrogens (H), 1 sulfur (S), 4 oxygens (O) from H₂SO₄.
- Right side: 1 potassium (K), 1 sulfur (S), 4 oxygens (O) in KHSO₄, and 2 hydrogens (H) in water, totaling 2 H.
- Both sides equal (1 K, 1 S, 6 O, and 2 H).
- Balanced!
The correct answer is D) \( KOH + H_2SO_4 \rightarrow KHSO_4 + H_2O \).