Problem 44 - Chemistry An Atoms First Approach

Question

Arsenic reacts with oxygen to form oxides that react with water in a manner analogous to that of the phosphorus oxides. Write balanced chemical equations describing the reaction of arsenic with oxygen and the reaction of the resulting oxide with water.

Step-by-Step Solution

Answer

1) Arsenic reacts with oxygen to form arsenic trioxide: \(4 \times As + 3 \times O_2 \rightarrow 2 \times As_2O_3\) 2) The resulting arsenic trioxide reacts with water to form arsenous acid: \(1 \times As_2O_3 + 3 \times H_2O \rightarrow 2 \times H_3AsO_3\)

Step 1: Determine Arsenic's Oxide Formation with Oxygen

First, we need to find the chemical formula of the oxide formed when arsenic reacts with oxygen. Arsenic (As) belongs to group 15 (Nitrogen group) of the periodic table, and its common oxidation state is +3. Thus, arsenic can react with oxygen (O₂) to form arsenic trioxide (As₂O₃) as follows: 2 As + 3 O₂ → 2 As₂O₃ Now, let's balance the equation: \(4 \times As + 3 \times O_2 \rightarrow 2 \times As_2O_3\)

Step 2: Determine Arsenic Trioxide Reaction with Water

Since the phosphorus oxides react with water to form acids, the arsenic trioxide will behave similarly and react with water to form an acid. Arsenic trioxide reacts with water to form arsenous acid (H₃AsO₃) as: As₂O₃ + 3 H₂O → 2 H₃AsO₃ Now, let's balance the equation: \(1 \times As_2O_3 + 3 \times H_2O \rightarrow 2 \times H_3AsO_3\) In summary, 1) Arsenic reacts with oxygen to form arsenic trioxide: \(4 \times As + 3 \times O_2 \rightarrow 2 \times As_2O_3\) 2) The resulting arsenic trioxide reacts with water to form arsenous acid: \(1 \times As_2O_3 + 3 \times H_2O \rightarrow 2 \times H_3AsO_3\)