Question

To prepare 0.1N working standard solution in 250ml distilled water from stock standard solution 20% Na2CO3 in 50ml of distilled water, and knowing that the A.wt of Na=23, O=16, C=12, what volume of the stock solution should be used?

A) 5 ml
B) 8.5 ml
C) 5.8 ml
D) 3 ml

Answer 1

To prepare a 0.1N working standard solution in 250 ml of distilled water from a stock standard solution of 20% Na₂CO₃ in 50 ml of distilled water, approximately 52.9 ml of the stock solution should be used. None of the given choices is correct.

Step-by-step explanation:

To prepare a 0.1N working standard solution in 250 ml of distilled water from a stock standard solution of 20% Na₂CO₃ in 50 ml of distilled water, we can use the dilution formula:

C1V1 = C2V2

Where C1 is the concentration of the stock solution, V1 is the volume of the stock solution used, C2 is the desired concentration of the working standard solution, and V2 is the final volume.

In this problem, the stock solution is 20% Na₂CO₃, which means it contains 20 grams of Na₂CO₃ in 100 ml of water. Using the molar masses of Na, O, and C, we can calculate the molarity of the stock solution:

Molarity = (20 grams/100 ml) * (1 mole/106 grams) = 0.189 M

To prepare a 0.1N working standard solution, we can substitute the given values into the dilution formula:

(0.189 M)(V1) = (0.1 N)(0.25 L)

V1 = (0.1 N)(0.25 L)/(0.189 M)

V1 = 0.0529 L = 52.9 ml

Therefore, approximately 52.9 ml of the stock solution should be used.

Hence, all options are incorrect.