diluting Solutions

Question

Potassium permanganate tablets are available in one gram tablets. The tablets are used to prepare 400mL of a 1:20 potassium permanganate solution.

How many grams of potassium permanganate are needed?

How many tablets of potassium permanganate are needed?

Answer 1

The expression 1:20 means 1 gram of solute in 20 grams of solvent. If water is the solvent, then 1 gram = 1 milliliter.

 

We can write a proportion which is 1 gram of solute is to 20 grams of solvent as x grams of solute is to 400 grams of solvent.

 

When we solve the proportion, the answer is 20 grams of potassium permanganate (KMnO₄).

 

Since the tablets contain 1 gram of potassium permanganate, we will need 20 tablets.