Question

Remember units and how much water is added to make the final volume. Show your work (c1v1=c2v2)

A	You have a 100% ETOH solution. Make 50mL of 70% ETOH (ETOH=ethanol)
B	You have 70% ETOH solution. Please make a 100mL solution of 30% ETOH.
C	You have a 1:10 solution of PBS. Can you make a 1L solution of 2X PBS? Why or why not?
D	Make a 1000uL 1/5 solution of red dye from a ½ solution.
E	I isolated DNA from some cells and got 342ng/uL. Make a 50 uL solution of 50ng/uL. How much DNA total is in your 50uL solution.

Answer 1

A) C1 *V1 =C2 *V2

100*X= 70*50 where X is the volume of 100% ethanol to be taken

X=3500/100 =35 ml of 100 % ethanol

Amount of water to be added to make 50ml of 70% ethanol =50-35=15ml

B) C1* V1= C2*V2

70*X=30*100 where X is the volume of 70% ethanol to be taken

X =3000/70 =42.8 ml of 70% ethanol

Amount of water to be added to make 100ml of 30% ethanol =100-42.8 =57.2 ml

C) 1: 10 PBS solution is a 10 times diluted solution of 1X PBS. As 2X PBS is more concentrated than 1:10 PBS,1:10 PBS cannot serve as a stock solution to make 2X PBS. In order to make the 1:10 PBS into 2X PBS salts have to be added.

D) C1* V1= C2*V2

1/2 *X= 1/5* 1000 where X is the volume of 1/2 dye to be taken

X=2*1000/5 =400 ul

Amount of water to be added to make 1000ul of 1/5 dye =1000-400= 600ul

E) C1* V1= C2*V2

342* X =50* 50 where X is the volume of 342ng/ul DNA to be taken

X = 2500/342 = 7.3 ul

Amount of water to be added to make 50ul of 50ng\ul DNA =50-7.3099 = 42.7 ul

1 ul contains 50 ng DNA

Amount of DNA in 50ul of 50ng\ul DNA = 50*50=2500 ng DNA