The student should use 1.0 × 10³ µL of clarified yeast extract.
The first question is, How much 100 % ethanol is needed to make 1.3 mL of 26 % ethanol?
This is a standard dilution calculation.
So you need to add enough clarified extract to make a total of 1.3 mL of solution.
How much extract is needed?
If there is no change of volume on mixing,
Note: The answer can have only 2 significant figures, because that is all you gave for the volume of the sample. If you need more precision, you will have to recalculate.
You would need
Here's how you'd go about solving this problem. You know that you must mix ethanol and clarified yeast extract together to get a
Now, I'm assuming you're dealing with a
If ethanol is your solute, a
This means that the volume of clarified yeast extract must be
Rounded to two sig figs, the answer should be