Question

Prepare 0.1N working standard solution in 250ml distilled water from stock standard solution 20% Na2CO3 in 50ml of distilled water. If you know that the A.wt of Na=32, O=16, C=12, what is the way I should follow to get the answer?

a. Dissolve 16g of Na2CO3 in 250ml of distilled water
b. Dissolve 40g of Na2CO3 in 250ml of distilled water
c. Dissolve 8g of Na2CO3 in 250ml of distilled water
d. Dissolve 20g of Na2CO3 in 250ml of distilled water

Answer 1

To prepare a 0.1N sodium carbonate solution, 1.325 grams of Na2CO3 are required for 250 mL of solution, which is not among the provided options.

Step-by-step explanation:

The question relates to preparing a 0.1N sodium carbonate (Na2CO3) solution. Normality (N) is a measure of concentration equivalent to molarity (M) multiplied by the number of equivalents per mole of a substance. Since Na2CO3 can supply two equivalents of Na+ per mole, the equivalent weight of Na2CO3 is half of its molar mass. To calculate the mass of Na2CO3 needed:

Molar mass of Na2CO3 = (2 × 32) + 12 + (3 × 16) = 106 g/mol

Equivalent weight of Na2CO3 = 106 g/mol ÷ 2 = 53 g/eq.

To prepare a 0.1N solution, we need 0.1 eq/L × 53 g/eq = 5.3 g/L.

Since we are preparing 250 mL, we need (5.3 g/L) × (0.250 L) = 1.325 g of Na2CO3.

None of the options provided matches the correct mass required. Therefore, the correct answer is not listed among the options given.