The water equivatent of a 400 g copper calorimeter (specific heat `=0.1 "cal"//g^(@)C`)

Options

A. 40 g
B. 4000 g
C. 200 g
D. 4g

Explanation

To find the water equivalent of a 400 g copper calorimeter with a specific heat of 0.1 cal/g°C, we can use the formula for water equivalent:

\[ \text{Water Equivalent} = \frac{m \cdot C_c}{C_w} \]

where:
- \( m \) = mass of the copper calorimeter (in grams)
- \( C_c \) = specific heat of copper (in cal/g°C)
- \( C_w \) = specific heat of water (in cal/g°C)

### Step-by-Step Solution:

1. **Identify the given values:**
- Mass of copper calorimeter, \( m = 400 \, \text{g} \)
- Specific heat of copper, \( C_c = 0.1 \, \text{cal/g°C} \)
- Specific heat of water, \( C_w = 1 \, \text{cal/g°C} \)

2. **Substitute the values into the water equivalent formula:**
\[ \text{Water Equivalent} = \frac{400 \, \text{g} \cdot 0.1 \, \text{cal/g°C}}{1 \, \text{cal/g°C}} \]

3. **Calculate the numerator:**
\[ 400 \, \text{g} \cdot 0.1 \, \text{cal/g°C} = 40 \, \text{cal} \]

4. **Divide by the specific heat of water:**
\[ \text{Water Equivalent} = \frac{40 \, \text{cal}}{1 \, \text{cal/g°C}} = 40 \, \text{g} \]

5. **Conclusion:**
The water equivalent of the 400 g copper calorimeter is **40 g**.

### Final Answer:
**Water Equivalent = 40 g**

---