chemistry Preparation of Solutions: Calculate the volume of stock solution neede
ID: 892770 • Letter: C
Question
chemistry Preparation of Solutions: Calculate the volume of stock solution needed in each ease to make the assigned standard solution: A standard solution with a concentration of 4 mg/L caffeine standard in a 10-mL volumetric flask using a stock solution of 100 ppm caffeine. A standard solution with a concentration of 8 mg L benzoic acid in a 10-mL volumetric flask using a stock solution of 100 ppm benzoic acid. A standard solution containing 12 mg/L caffeine and 6 mg/L benzoic acid in a 10-mL volumetric flask using the primary stock solutions of 1000 ppm caffeine and 1000 ppm benzoic acid.Explanation / Answer
2. preparation of solutions,
using C1V1 = C1V2
where,
C1 = 4 mg/L = 4ppm
V1 = 10 mL
C2 = 100 ppm
V2 = unknown
Feed values,
4 x 10 = 100 x V2
V2 = 0.4 mL
So we would required 0.4 ml of 100 ppm stock solution to prepare a 10 ml of 4 mg/L solution.
b. again, C1V1 = C2V2
where,
C1 = 8 mg/L = 8 ppm
V1 = 10 ml
C2 = 100 ppm
V2 = unknown
Feed values,
V2 = 8 x 10/100 = 0.8 ml
So we would need 0.8 ml of 100 ppm stock solution to prepare a 10 ml of 8 mg/L solution.
c. Using C1V1 = C2V2
First, caffeine
C1 = 12 mg/L = 12 ppm
V1 = 10 ml
C2 = 1000 ppm
V2 = unknown
Feed values,
V2 = 12 x 10/1000 = 0.12 ml
Then for benzoic acid,
C1 = 6 mg/L = 6 ppm
V1 = 10 ml
C2 = 1000 ppm
V2 = unknown
Feed values,
V2 = 6 x 10/1000 = 0.06 ml
So we would need 0.12 ml of 1000 ppm caffeine stock solution and 0.06 ml of 1000 ppm benzoic acid stock solution to prepare a 10 ml of 12 mg/L caffeine and 6 mg/L benzoic acid final solution.
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