How many liters of water must be added to 8 liter of a 40%acid solution to obian a 10% acid solution

Question

How to I set this up 

Answer 1

The equation you need to use for this kind of problems is V1 XS1 = V2 x S2

V1= 8 Lit S1 = 40%. S2 = 10%  you need to calculate V2

 

V2= (V1x S1)/S2 =( 8 x 40)/10 = 32 

 

Thus you need to dilute 8 lit 40% acid with water to make up the volume to 32 lit (you need to add 32-8 =24 lit Water)

Answer 2

The equation must be in only acid or water, not both.

Since water is being added, the equation shall be for water.

40% acid = 60% water, 10% acid = 90% water

 

0.6(8) + 1.0x = 0.9(8 + x)

 

Can you solve for x?