Answer:
8 liters of 15% NaCl solution should be mixed with 2 L of a 20% NaCl solution to obtain a 16% NaCl solution
Step-by-step explanation:
The method employed here is known as alligation technique.
Alligation is a method used to calculate the proportion of any two solutions to be mixed to prepare final solution of required concentration.
Let the number of liters of the 15% NaCl solution be X
A mixture of X liters of 15% NaCl + 2 liters of 20% NaCl gives X + 2 liters of a solution whose concentration is 16%
X * 15% + 2 * 20% = 16% * X + 2
0.15X + 2 * 0.2 = 0.16 X + 0.16 * 2
0.15X + 0.4 = 0.16X + 0.32
0.16X - 0.15X = 0.4 - 0.32
0.01X = 0.08
X = 0.08/0.01
X = 8 liters
Therefore, 8 liters of 15% NaCl solution should be mixed with 2 L of a 20% NaCl solution to obtain a 16% NaCl solution