You need a 30% alcohol solution. On hand, you have a 270 mL of a 70% alcohol mixture. How much pure water will you need to add to obtain the desired solution?
A) Write an equation using the information as it is given above that can be used to solve this problem. Use x as your variable to represent the amount of pure water you need to use.
Equation:
how much mL of pure water to obtain
how much mL of the desired 30% solution
Let x represent the amount of pure water needed to obtain the desired 30% solution.
The amount of alcohol in the mixture before adding water is 270 mL * 0.70 = 189 mL.
When x mL of pure water is added, the total volume of the solution becomes 270 mL + x mL.
The amount of alcohol in the final solution is (270 mL * 0.70) / (270 mL + x mL).
Since we want a 30% alcohol solution, we can set up the following equation:
(270 mL * 0.70) / (270 mL + x mL) = 0.30
Now we can solve this equation to find the amount of pure water needed.