Question

.84 g of metal carbonate react's exactly with 40 ml of N/2 H2SO4. the equivalent weight of metal is

Answer 1

Answer: Equivalent weight of metal is 42 grams

Explanation: We are given Normality of $H_SO_4$ as 0.5M.

Molarity of $H_SO_4$ is calculated by:

$Normality=Molarity\times (\text{Valence factor})$

Valence factor of sulfuric acid = 2

$\text{Molarity of }H_2SO_4=\frac{0.5}{2}=0.25$

Formula for molarity is:

$Molarity=\frac{Moles}{\text{Volume (in mL)}}\times 1000$

$\text{Moles of }H_2SO_4=\frac{0.25\times 4}{1000}=0.01moles$

Moles can be written as:

$Moles=\frac{\text{Given mass}}{\text{Molar mass}}$

$\text{Molar mass of }H_2SO_4=98g/mol$

$\text{Mass of }H_2SO_4=0.01mol\times 98g/mol=0.98g$

As, equivalence of metal carbonate = equivalence of sulfuric acid

Equivalence can be calculated as:

$Equivalence=\frac{\text{Mass of substance}}{\text{Equivalent weight of that substance}}$

Equivalent weight of $H_2SO_4=\frac{98}{2}=49$

Mass of sulfuric acid = 0.98 g

Equivalent weight of metal carbonate = x grams

Mass of metal carbonate = 0.84 g

Putting the values in above equation, we get

$\frac{0.98}{49}=\frac{0.84}{x}$

x = 42 grams

Answer 2

Answer : The equivalent weight of metal is, 420 grams

Explanation :

As we are given that,

Normality of $H_2SO_4$ as 0.5 M.

Now we have to calculate the molarity of $H_2SO_4$

$Normality=Molarity\times (\text{Valence factor})$

Valence factor of sulfuric acid = 2

$\text{Molarity of }H_2SO_4=\frac{0.5}{2}=0.25$

Now we have to calculate the moles of $H_2SO_4$

$Molarity=\frac{Moles}{\text{Volume (in mL)}}\times 1000$

$\text{Moles of }H_2SO_4=\frac{0.25\times 4}{1000}=0.001moles$

Now we have to calculate the mass of $H_2SO_4$

$Moles=\frac{\text{Given mass}}{\text{Molar mass}}$

$\text{Molar mass of }H_2SO_4=98g/mol$

$\text{Mass of }H_2SO_4=0.001mol\times 98g/mol=0.098g$

As, equivalence of metal carbonate = equivalence of sulfuric acid

Equivalence can be calculated as :

$Equivalence=\frac{\text{Mass of substance}}{\text{Equivalent weight of that substance}}$

Equivalent weight of $H_2SO_4=\frac{98}{2}=49$

Mass of sulfuric acid = 0.098 g

Equivalence of $H_2SO_4$ = $\frac{0.098}{49}$     .........(1)

Equivalent weight of metal carbonate = x grams

Mass of metal carbonate = 0.84 g

Equivalence of metal carbonate = $\frac{0.84}{x}$   ........(2)

Now equating 1 and 2, we get:

$\frac{0.098}{49}=\frac{0.84}{x}$

x = 420 grams

Therefore, the equivalent weight of metal is, 420 grams