The normality of conc. HCl used in the laboratory is

Options

A. 10 N
B. 8 N
C. 4 N
D. 2 N

Answer

To determine the normality of concentrated HCl used in the laboratory, we can follow these steps:

### Step 1: Understand the Concentration of HCl
Concentrated hydrochloric acid (HCl) is typically available in different concentrations. The most common concentration used in laboratories is 36% HCl by weight.

### Step 2: Know the Density of HCl
The density of concentrated HCl is approximately 1.18 g/mL. This information is crucial for calculating the normality.

### Step 3: Calculate the Mass of HCl in 1 Liter
To find the mass of HCl in 1 liter (1000 mL) of concentrated HCl:
- Use the density to find the mass:
\[ \text{Mass} = \text{Density} \times \text{Volume} = 1.18 \, \text{g/mL} \times 1000 \, \text{mL} = 1180 \, \text{g} \]

### Step 4: Calculate the Mass of HCl in the Solution
Now, calculate the mass of HCl in the 36% solution:
- Since it is 36% by weight:
\[ \text{Mass of HCl} = 36\% \times 1180 \, \text{g} = 0.36 \times 1180 \, \text{g} = 425.28 \, \text{g} \]

### Step 5: Convert Mass of HCl to Moles
Next, convert the mass of HCl to moles using its molar mass (HCl has a molar mass of approximately 36.46 g/mol):
\[ \text{Moles of HCl} = \frac{\text{Mass of HCl}}{\text{Molar Mass of HCl}} = \frac{425.28 \, \text{g}}{36.46 \, \text{g/mol}} \approx 11.65 \, \text{mol} \]

### Step 6: Calculate Normality
Normality (N) is defined as the number of equivalents of solute per liter of solution. For HCl, which is a monoprotic acid, the number of equivalents is equal to the number of moles:
\[ \text{Normality} = \text{Moles of HCl in 1 L} = 11.65 \, \text{N} \]

### Step 7: Conclusion
In the laboratory, the normality of concentrated HCl (36% solution) is approximately 11.65 N. However, it is commonly rounded to 10 N for practical purposes.

### Final Answer
The normality of concentrated HCl used in the laboratory is approximately **10 N**.

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