The amount of water to be added to 100 c.c. of 1 normal HCl solution to make it decinormal is -

Options

A. 900 c.c.
B. 850 c.c.
C. 400 c.c.
D. 600 c.c.

Answer

To solve the problem of how much water to add to 100 c.c. of 1 normal HCl solution to make it decinormal (0.1 normal), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Initial Conditions**:
- We have 100 c.c. (or 100 ml) of 1 normal HCl solution.
- The goal is to dilute this solution to a decinormal (0.1 normal) concentration.

2. **Calculate the Initial Milli-equivalents**:
- The formula for milli-equivalents is given by:
\[ \text{Milli-equivalents} = \text{Normality} \times \text{Volume (in liters)} \]
- For the initial solution:
\[ \text{Milli-equivalents} = 1 \, \text{N} \times 0.1 \, \text{L} = 0.1 \, \text{equivalents} = 100 \, \text{milli-equivalents} \]

3. **Set Up the Equation for the Final Conditions**:
- After dilution, we want the normality to be 0.1 N. Let \( V_2 \) be the final volume in liters after dilution.
- The milli-equivalents after dilution will also be:
\[ \text{Milli-equivalents} = 0.1 \, \text{N} \times V_2 \]
- Since the milli-equivalents must remain constant before and after dilution:
\[ 100 \, \text{milli-equivalents} = 0.1 \, \text{N} \times V_2 \]

4. **Solve for the Final Volume \( V_2 \)**:
- Rearranging the equation gives:
\[ V_2 = \frac{100 \, \text{milli-equivalents}}{0.1 \, \text{N}} = 1000 \, \text{ml} \]

5. **Calculate the Amount of Water to Add**:
- The amount of water to be added is the final volume minus the initial volume:
\[ \text{Water to add} = V_2 - \text{Initial Volume} = 1000 \, \text{ml} - 100 \, \text{ml} = 900 \, \text{ml} \]

### Final Answer:
The amount of water to be added to 100 c.c. of 1 normal HCl solution to make it decinormal is **900 ml**.