To dissolve 0.9 g metal, 100 mL of 1 N HCl is used. What is the equivalent weight of metal?

Options

A. 7
B. 9
C. 10
D. 6

Answer

To find the equivalent weight of the metal, we can follow these steps:

### Step 1: Understand the concept of Normality
Normality (N) is defined as the number of equivalents of solute per liter of solution. In this case, we have a 1 N solution of HCl.

### Step 2: Calculate the number of equivalents of HCl used
Given that we have 100 mL of 1 N HCl, we can calculate the number of equivalents of HCl used:
\[ \text{Number of equivalents of HCl} = \text{Normality} \times \text{Volume (in L)} \]
\[ \text{Number of equivalents of HCl} = 1 \, \text{N} \times 0.1 \, \text{L} = 0.1 \, \text{equivalents} \]

### Step 3: Relate equivalents of HCl to the metal
Since HCl is a strong acid and fully dissociates, 1 equivalent of HCl will react with 1 equivalent of metal. Therefore, the number of equivalents of the metal will also be 0.1 equivalents.

### Step 4: Calculate the equivalent weight of the metal
The equivalent weight of a substance is defined as the mass of the substance that combines with or displaces 1 mole of hydrogen (or generates 1 gram of H2). The formula to calculate equivalent weight is:
\[ \text{Equivalent weight} = \frac{\text{Mass of metal}}{\text{Number of equivalents}} \]
Substituting the values we have:
\[ \text{Equivalent weight} = \frac{0.9 \, \text{g}}{0.1 \, \text{equivalents}} = 9 \, \text{g/equiv} \]

### Conclusion
The equivalent weight of the metal is 9 grams.

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