Achemist needs 90 milliliters of a 72% solution but has only 68% and 77% solutions available. find how many milliliters of the 68% solution should be mixed with the 77% solution to get the desired strength.

Mix 50 mL of the 68% solution with 40 mL of the 77% solution to make 90 mL of the 72% solution.

Explanation:

Let the volume required of the 68% solution be mL. The volume of the 68% solution and the 77% solution shall add up to 90 mL. Thus the volume required of the 77% solution shall be mL.

The amount of solute in the 72% solution will be:

.

The mL of the 68% solution will contribute:

.

The mL of the 77% solution will contribute:

.

The two values shall add up to . That is:

.

.

.

In other words, there need to be

why do the isotopes of a particular element behave differently in nuclear reactions but the same in chemical reactions? chemical reactions involve changes to electrons in an atom; isotopes do not differ in electrons, and so they react the same way during chemical changes.