Which metal will react readily with cold water?
a. Gold
b. Silver
c. Magnesium
d. Calcium

Options

A. Gold
B. Silver
C. Magnesium
D. Calcium

Explanation

To determine which metal reacts readily with cold water among the given options (Gold, Silver, Magnesium, and Calcium), we can follow these steps:

### Step-by-Step Solution:

1. **Understand Reactivity Series**:
- The reactivity series is a list of metals arranged in order of decreasing reactivity. Metals at the top of the series react more vigorously with water and acids compared to those lower down.

2. **Identify the Position of Each Metal**:
- Gold and Silver are located at the bottom of the reactivity series, making them the least reactive metals. They do not react with water.
- Magnesium is above Gold and Silver in the reactivity series but below Calcium. It does not react with cold water but can react with hot water to form magnesium hydroxide and hydrogen gas.
- Calcium is higher in the reactivity series than Magnesium. It reacts readily with cold water to produce calcium hydroxide and hydrogen gas.

3. **Analyze the Reaction with Cold Water**:
- **Gold**: No reaction with cold water.
- **Silver**: No reaction with cold water.
- **Magnesium**: No reaction with cold water; reacts only with hot water.
- **Calcium**: Reacts readily with cold water.

4. **Conclusion**:
- Based on the reactivity series and the behavior of these metals with cold water, Calcium is the only metal among the options that reacts readily with cold water.

### Final Answer:
**Calcium (d)** is the metal that will react readily with cold water.

---