`1g` of the carbonate of a metal was dissolved in `25mL` of `N-HCl`. Te resulting liquid `5 mL` of `N-NaOH` for neutralisation. The `Ew` of the metal `Carbonate is

Options

A. 50
B. 30
C. 20
D. None

Explanation

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

### Step 1: Understand the Reaction
When the carbonate of a metal (MCO₃) is dissolved in hydrochloric acid (HCl), it reacts to form a salt, water, and carbon dioxide. The reaction can be represented as:
\[ \text{MCO}_3 + 2 \text{HCl} \rightarrow \text{MCl}_2 + \text{H}_2\text{O} + \text{CO}_2 \]

### Step 2: Calculate the Equivalent of HCl
Given that 25 mL of 1 N HCl is used, we can calculate the equivalents of HCl:
\[ \text{Equivalents of HCl} = \text{Normality} \times \text{Volume (L)} \]
\[ \text{Equivalents of HCl} = 1 \, \text{N} \times 0.025 \, \text{L} = 0.025 \, \text{equivalents} \]

### Step 3: Calculate the Equivalent of NaOH
Next, we know that 5 mL of NaOH is required for neutralization. We can calculate the equivalents of NaOH:
\[ \text{Equivalents of NaOH} = \text{Normality} \times \text{Volume (L)} \]
\[ \text{Equivalents of NaOH} = 1 \, \text{N} \times 0.005 \, \text{L} = 0.005 \, \text{equivalents} \]

### Step 4: Set Up the Equation
From the reaction, we know that the equivalents of the carbonate will be equal to the equivalents of HCl minus the equivalents of NaOH:
\[ \text{Equivalents of MCO}_3 = \text{Equivalents of HCl} - \text{Equivalents of NaOH} \]
\[ \text{Equivalents of MCO}_3 = 0.025 - 0.005 = 0.020 \, \text{equivalents} \]

### Step 5: Calculate the Equivalent Weight
The equivalent weight (Ew) of the metal carbonate can be calculated using the formula:
\[ \text{Ew} = \frac{\text{Weight of the substance}}{\text{Equivalents}} \]
Given that the weight of the carbonate is 1 g:
\[ \text{Ew} = \frac{1 \, \text{g}}{0.020 \, \text{equivalents}} = 50 \, \text{g/equivalent} \]

### Conclusion
Thus, the equivalent weight of the metal carbonate is **50 g/equivalent**.

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