Question

To reduce 16 ounces of a 25% solution of antiseptic to a 10% solution, how much distilled water should a nurse add?

Answer 1

Answer:

24 ounces

Step-by-step explanation:

Here's a more intuitive approach to use here.

You know that your initial solution has a percent concentration, presumably volume by volume, of  

25

%

. This means that any volume of this solution contains  

1

part solute and  

3

parts solvent.

The target solution must have a concentration of  

10

%

, which means that any volume of this solution will contain  

1

part of solute and  

9

parts solvent.

Your starting solution has a volume of  

16

ounces, or  

4

parts, each with a volume of  

4

ounces.

In order to get to a solution that has a total of  

10

parts, you must add  

6

parts of solvent to the initial solution. Since we know that

1 part  

=

4 ounces

it follows that you must add

6

parts

⋅

4 ounces

1

part solvent

=

24 ounces

of distilled water, which is your solvent, to the initial solution.

The target solution will contain  

1

part solute and  

9

parts distilled water for a total of  

10

parts of solution, and hence have a percent concentration of  

10

%

.