Question

1a) How many ml of 20% sucrose should be used to make 2 ml of 5% sucrose?

1b) How is 640 ml of 0.5x buffer prepared from an 8x stock?

Please show all work! Thank you and I will mark it thumbs up if everything is correct.

Answer 1

1a)

concentration of sucrose C1 = 20 %

final concentration C2 = 5 %

final volume V2 = 2 mL

initial volume V1 = ??

C1 V1 = C2 V2

20 x V1 = 5 x 2

V1 = 0.5 mL

volume of 20% sucrose should be used = 0.50 mL

1b)

concentration of stock C1 = 8x

C2 = 0.5 x

V2 = 640 mL

0.50 x 640 = 8x x V1

V = 40 mL

volume of 8x stock should used = 40 mL

40 mL of 8x stock is used to prepare 640 mL of 0.5 x buffer