1. You have 19.7 grams of a material and wonder how many moles were formed. Your friend tells you to multiply the mass by grams/mole. Is your friend correct?
Hint Set in the solution an

No. If you were to set up what the friend said it would look like this:

19.7g × ==>   ×

The above does not look right because the grams do not cancel out. If it's not cancelled, it would be included in your final answer, but you're looking for moles not grams.

When setting up a stoichiometry equation, you have to put the same unit of measurement (ex- grams, cm, mm, etc.) on the numerator of one side and the denominator of the other side.

This would cancel out the unit.

For example: If you wanted to find out how much of 320 cm are in a meter.

*there are 100 cm in 1 meter*

(1. always start with the given number!)

(2. set up the next fraction where you can cancel out cm)

× = 3.2 m

Going back, your friend would have to switch the units from grams/moles to moles/grams. It would cancel out grams, which would leave moles. Therefore, moles will be included in your final answer.

× = _?_ moles

answer; /// i do believe that the correct answer is (a) boiling

the answer is learned