Question

How much water must be evaporated from 32 ounces of a 7% salt solution to make a 8% salt​ solution? (Answer is in ounces)

Answer 1

.07*32 =ounces of salt = 2.24
so we have 29.76 ounces of water
so
2.24 = .08(water + salt)
2.24 = .08 (water + 2.24)
2.24 = .08 water + .18
2.06 = .08*water
water = 25.75
so
water removed = 29.76-25.75
about 4 oz

Answer 2

V = Volume of 7% salt solution = 32 ounces

s = Volume of salt in 7% salt solution

w = Volume of wather 7% salt solution


s = 7 % of 32 = ( 7 / 100 ) ∙ 32 =

0.07 ∙ 32 = 2.24 ounces

Volume of water in 7% salt solution:

w = 93 % of V =

93 % of 32 = ( 93 / 100 ) ∙ 32 =

0.93 ∙ 32 = 29.76 ounces


V1 = Volume of 8% salt solution

s1 = Volume of salt in 8% salt solution

w1 = Volume of wather 8% salt


In 8% salt​ solution 2.24 ounces of salt represent 8 % of volume

s1 = 2.24 ounces

s1 = 0.08 V1

2.24 = 0.08 V1

V1 = 2.24 / 0.08 = 28 ounces

92 % of this volume is wather.

w1 = 0.92 ∙ 28 = 25.76 ounces


∆w = w - w1 = 29.76 ounces - 25.76 ounces = 4 ounces

OR

∆V = V - V1 = 32 - 28 = 4 ounces

Answer 3

s / v = .07

s / (v - x) = .08

dividing ... (v - x) / v = 7 / 8

1 - x/v = 7/8 ... 1/8 = x/v ... x = v/8