Question

sodium metal reacts with water to form aqueous sodium hydroxide and hydrogen gas. which equation below best describes the balanced equation for this reaction?
2na + 2h₂o → 2naoh (aq) + h₂ (g)
na + h₂o → naoh (aq) + h₂ (g)
2na + h₂o → na₂oh (aq) + h (g)
na + h₂o → naoh (aq) + h (g)
s + h₂o → soh (aq) + h (g)

Explanation:

Step1: Recall the reaction of Na and H₂O

Sodium (Na) reacts with water (H₂O) to form sodium hydroxide (NaOH) and hydrogen gas (H₂). The unbalanced equation is \( \text{Na} + \text{H}_2\text{O}
ightarrow \text{NaOH} + \text{H}_2 \).

Step2: Balance the equation

• Balance Na: There are 1 Na on left, 1 on right (in NaOH). But after balancing H and O, we'll adjust.
• Balance O: 1 O on left (H₂O), 1 O on right (NaOH) – O is balanced for now.
• Balance H: Left has 2 H (H₂O), right has 1 H (NaOH) + 2 H (H₂) = 3 H. To balance H, multiply H₂O by 2, NaOH by 2: \( \text{Na} + 2\text{H}_2\text{O}

ightarrow 2\text{NaOH} + \text{H}_2 \). Now H: 4 on left (2×2), 4 on right (2×1 + 2×1).

• Balance Na: Now left has 1 Na, right has 2 Na (in 2NaOH). So multiply Na by 2: \( 2\text{Na} + 2\text{H}_2\text{O}

ightarrow 2\text{NaOH} + \text{H}_2 \). Now check all:

• Na: 2 left, 2 right.
• O: 2 left (2×1), 2 right (2×1).
• H: 4 left (2×2), 4 right (2×1 + 2×1).

Step3: Match with options

The balanced equation is \( 2\text{Na} + 2\text{H}_2\text{O}
ightarrow 2\text{NaOH}(aq) + \text{H}_2(g) \), which is the first option.

Answer:

\( 2\text{Na} + 2\text{H}_2\text{O}
ightarrow 2\text{NaOH}(aq) + \text{H}_2(g) \) (the first option in the list)