Question

A) Using a stock solution of copper in water (50ug/mL), calculate the volume of the stock solution needed to make a 7.5 ug/mL standard (5 mL total volume).

B) Constrcut 10 mL if a 3.5 ng/mL solution from a stock solution of 125 ug/mL DDT in acetone.

Answer 1

A) The formula is

C1×V1 = C2 × V2

Where,

C1 = initial concentration , 50ug/ml

V1 = initial Volume , ?

C2 = Final concentration,7.5ug/ml

V2 = Final Volume , 5ml

V1 = C2×V2/C1

= 7.5(ug/ml) × 5ml / 50(ug/ml)

= 0.75ml

So, the answer is 0.75ml

B) First convert ng to ug

1ng = 0.001ug

3.5ng = 0.0035ug

Now , Apply the above formula

V1 = C2 × V2/C2

= 0.0035(ug/ml) × 10ml /125(ug/ml)

= 0.00028ml

= 0.28uL

so, take 0.28uL from stock solution and make up it for 10ml using acetone