Approximately 0.6 ml of 78% acid solution has to be mixed with 12ml of a 10% acid solution to make 30% solution
Solution:
First, set up a table. Fill in the unknowns with variable "x"
"x" ml of 78% acid solution must be mixed with 12 ml of 10 % acid solution to make 30% acid solution
Let us solve for "x"
The table is attached below
From the table below, we can set up two equations
Sum of values of two salts = Value of mixture
Sum of values of two salts = 0.78x + 1.2
Value of mixture = 0.3(x + 12)
Sum of values of two salts = Value of mixture
Then, 0.78x + 1.2 = 0.3(x + 12)
0.78x + 1.2 = 0.3x + 3.6
0.78x – 0.36x = 3.6 – 1.2
4.2x = 2.4
x = 0.5714 ≈ 0.6
Hence, approximately 0.6 ml of 78% acid solution has to be mixed