# Molarity question

1. Jan 4, 2008

### oceanflavored

1. The problem statement, all variables and given/known data
another satII chem question:
Forty grams of sodium hydroxide is dissolved in enough water to make 1 liter of solution. What is the molarity of the solution?
(A) 0.25 M
(B) 0.5 M
(C) 1 M
(D) 1.5 M
(E) 4 M

2. Relevant equations

Molarity = (number of moles of solute) / (1 L of solution)

3. The attempt at a solution
well, i converted 40 g of NaOH to moles so...
40 g NaOH x (1 mol NaOH) / (40 g NaOH)= 1 mol
so...
Molarity = (1 mol) / (1 L) = 1 M

but the book says the answer is (A) & their explanation is...
NaOH is 40 g/mol. 10 g is 10/40 or 0.25 mol in 1 L or 0.25 M

i have no idea, how they're getting the 10.
and would appreciate any help at alll.

thank you so much guys

also; if anyone knows how to insert division signs to make the presentation look ANY better, because right now it looks messy!...i was trying to use the underline thing, but the formatting got all messed up!

2. Jan 4, 2008

3. Jan 4, 2008

### mit

40 gr in 1 liter gives 1 mol NaOH solution, I think the book is wrong because I can't see any reason for using 10 gr that is not given in the question.

4. Jan 4, 2008

### oceanflavored

thanksyou :)

YAY!
thank you so much guys!
i was feeling a little down, as to why i wasn't getting this little molarity problem.
and two physics-forum people agreeing with me makes me feel a whole lot better.
thanks once again!

5. Jan 4, 2008

### chemisttree

Do you think it is possible that someone penciled in the '4' in 40 from what was originally a '1'? If so, that's a pretty dirty trick.