Question

question 1
in the reaction:
ca(s) + h₂o(l) ---> ca(oh)₂(s) + h₂(g)
what is reducing agent and what is oxidizing agent?
☐ ca is the oxidizing agent
☐ hydrogen is the oxidizing agent
☐ water is the oxidizing agent
☐ water is the reducing agent
☐ ca is the reducing agent

Explanation:

Step1: Determine oxidation states

First, find the oxidation states of each element. In \( \text{Ca}(s) \), Ca has an oxidation state of 0. In \( \text{H}_2\text{O}(l) \), H is +1 and O is -2. In \( \text{Ca(OH)}_2(s) \), Ca is +2, O is -2, and H is +1. In \( \text{H}_2(g) \), H is 0.

Step2: Identify oxidation and reduction

• For Ca: Oxidation state changes from 0 (in \( \text{Ca} \)) to +2 (in \( \text{Ca(OH)}_2 \)). This is an increase, so Ca is oxidized. A substance that is oxidized is a reducing agent.
• For H in \( \text{H}_2\text{O} \): Oxidation state changes from +1 (in \( \text{H}_2\text{O} \)) to 0 (in \( \text{H}_2 \)). This is a decrease, so H is reduced. The substance being reduced ( \( \text{H}_2\text{O} \) here, since H is in \( \text{H}_2\text{O} \)) is the oxidizing agent.

Step3: Evaluate options

• "Ca is the oxidizing agent": Incorrect, Ca is oxidized (reducing agent).
• "Hydrogen is the oxidizing agent": Incorrect, H in \( \text{H}_2\text{O} \) is reduced, but the oxidizing agent is \( \text{H}_2\text{O} \), not elemental H.
• "Water is the oxidizing agent": Correct, as H in \( \text{H}_2\text{O} \) is reduced.
• "Water is the reducing agent": Incorrect, water is the oxidizing agent.
• "Ca is the reducing agent": Correct, as Ca is oxidized.

Answer:

C. Water is the oxidizing agent, E. Ca is the reducing agent (assuming options are labeled as: A. Ca is the oxidizing agent, B. Hydrogen is the oxidizing agent, C. Water is the oxidizing agent, D. Water is the reducing agent, E. Ca is the reducing agent)