The thermal capacity of a substance is 5 `cal//^@F`. What is water equivalent of the substance

Options

A. 5g
B. 9g
C. `(25)/9g`
D. 5kg

Explanation

To solve the problem of finding the water equivalent of a substance given its thermal capacity, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Thermal Capacity**:
- Thermal capacity (C) of a substance is defined as the amount of heat required to change its temperature by one degree. It is given in units such as calories per degree (cal/°F).

2. **Identify the Given Data**:
- The thermal capacity of the substance is given as \( C = 5 \, \text{cal/°F} \).

3. **Relate Thermal Capacity to Water Equivalent**:
- The water equivalent (W) of a substance is defined as the mass of water that would absorb the same amount of heat for the same temperature change. The water equivalent is numerically equal to the thermal capacity of the substance when expressed in calories.
- Therefore, \( W = C \).

4. **Calculate the Water Equivalent**:
- Since the thermal capacity is \( 5 \, \text{cal/°F} \), the water equivalent is:
\[ W = 5 \, \text{grams} \]

5. **Conclusion**:
- The water equivalent of the substance is \( 5 \, \text{grams} \).

### Final Answer:
The water equivalent of the substance is **5 grams**.