please help solve this i dont know how

Question

how many ounces of water should a chemist remove from 20 ounces of a 20% sulfuric acid solution to increase it to 40% sulfuric acid solution?water is removed by boiling.

Answer 1

Since the information requested is about water, the concentrations must be in terms of water.

 

Starting 20 oz of 80% water

Subtract x oz of 100% water

Result 20 - x oz of 60% water

 

0.8(20) - 1x = 0.6(20 - x)        distribute

16 - x = 12 - 0.6x                  add x to both sides

16 = 12 + 0.4x                      subtract 1.2 from both sides

4 = 0.4x                                divide both sides by 0.4

10 = x

 

Remove 10 ounces of water.

 

Check:

 

0.8(20) - 10 = 0.6(20 - 10)

16 - 10 = 0.6(10)

 6 = 6

 

Answer 2

If you want to double the concentration, half the solute, so boil off half of it. (boil off 10 ounces).