System Applications

Question

A chemistry teacher needs to make a 42% sulphuric acid solution. The acid solutions available are 4 liters of 30% sulphuric acid and 50% sulphuric acid, by volume. How many liters of the 50% sulphuric acid solution must be mixed with the 4 liters in order to make the 42% sulphuric acid solution?

 

Let x = 30%

Answer 1

4(.3) + z(.5) = (4+z)(.42)

1.2 + .5z = 1.68 + .42z

.08z = .48

z= 6 liters