Question

(Please help!) One way to describe the concentration of an acid is as a percent by volume. For example, in 40 mL of a 30% acid solution, the volume of pure acid is 40 x 30/100 or 12 mL, and the volume of water is 40-12 or 28 mL. If 5 mL of pure acid is mixed with 20 mL of water to give 25 mL of acid solution, the concentration of the solution is given by 5/25 x 100% = 20 %. If water is mixed with 50 mL of 40% acid solution, write an equation that describe the acid concentration, C(x), as a function of the volume of water added, x.

Answer 1

The answer is C(x) = (20/50 + x)*100%, but why?

Answer 2

C(x) = [20/(x+50)] *100

Answer 3

yup but why though?

Answer 4

50 mL of 40% acid solution contains 20mL of acid and 30mL of water, so if you add xmL of water the solution will be : (amount of acid)/(total solution)*100
amount of acid is 20mL. Total mLof solution is x+ 50mL

Answer 5

got it?

Answer 6

How did you know that the acid solution containes 20 mL of acid and 30 mL of water?

Answer 7

it says that is 40%. And you have 50mL. So 50*40/100 =20

Answer 8

what is left is water

Answer 9

got it?

Answer 10

ohh, i see.

Answer 11

thank you!

Answer 12

yw

Answer 13

Myko, sorry to ask you again: but how is the total mL of solution x + 50 mL? D:

Answer 14

x is the new water, 50 mL is 40% acid solution