1. 7 L of an acid solution was mixed with 3 L of a 15% acid solution to make a 29% acid solution. Find the percent concentration of the first solution.

Question

It's a word problem that I really don't understand at all. 

Answer 1

C₁ = concentration of first solution = ?

V₁ = volume of first solution = 1.7 L

C₂ = concentration of second solution = 15%
V₂ = volume of second solution = 3 L

C = concentration mixture = 29%
V = volume of mixture = V₁ + V₂ = (1.7 + 3) L = 4.7 L

 

Get C₁ from a weighted combination of volumes:

 

C₁V₁ + C₂V₂ = CV

 

C₁ = (CV - C₂V₂) / V₁ = [(29%)(4.7 L) - (15%)(3 L)] / (1.7 L) ≅ 53.7%