How Do I Solve This Chemistry Question: How Many Moles Are Contained In 25 G NaOH?Can You Please Explain Step By Step How I Would Solve This?

Question

How Do I Solve This Chemistry Question: How Many Moles Are Contained In 25 G NaOH?Can You Please Explain Step By Step How I Would Solve This?

2 Answers

Answer Question

Answer 1

You solve this by realizing
moles = (grams)/(grams/mole)

The grams/mole value of a substance is its molecular weight. That is found by adding the atomic weights of the constituent atoms. The atomic weights are ...
Na: 22.9898
O: 15.9994
H: 1.0079.
There is one atom of each in NaOH, so the molecular weight is the sum of these numbers: 39.9971.

moles = (25 g)/(39.9971 g/mol) = .625 moles.

Answer 2

Hello I am writing only to illuminate the inaccuracies as I see them, I do not want to step on toes. First I congratulate you the simple fact of coming to the correct answer, but how you have with the the relationships in a simple factor label method problem is this. The relationship is incorrect and the value used in place of their calculated value 39.99gm/mole is 25 gms?.

Using your equation as listed: Moles = (grams)/(grams/mole)
the answers written would yeild the answer moles = (25G)/(25G/mole NaOH)=625 G2/mole, NO Way

Even with the correct MW = 39.99/ 1mole NaOH
mole = (25G)(40G/mole) = 999.75 G2/mole

The PROPER EQUTION can always be obtained by first writing down what you have and where you want to go.

Moles = 25 gms NaOH x (1mole NaOH/39.99 gms) = 0.73 moles of NaOH.
This way the units of grams will cancell out and you are left with the desired units of moles.