How many moles of hydroxide ion are there in a 250 mL sample of 5.00 M solution of sodium hydroxide?

n=c/v

n=3M/.25L

n=12 mol

m=Mxn

m=58.443 g/mol x 12 mol

m=701.3 g

n= mol

c=concentration

v=volume

m=mass

M= molar mass

Tylerops:

I don't agree with this answer. Molarity is defined as Moles/Liters. In other Words Molarity is the concentration of a solution. In the above n= Concentration / Liters. That is equal to saying Moles=(Moles/liters)/ Liters. In the above question the concentration is (3 moles/ liter), or 3M.

Plus, how can it be possible to have 12 moles in 250ml when you only have 3 moles in each liter of the original solution?

Correct ANSWER:

3.00 M, or 3 moles per (L) "liter" calls for having 3 moles per liter of the solution. The question asks how many moles must be in 250ml of a solution that has 3 moles per Liter.

You must ask yourself what percent of 1 Liter is 250mls? Since there are a thousand ml in one liter, (1000ml=1L), then 250ml is exactly 25% of a Liter, or .25L.

So, 250ml can only hold 25% of the 3.00 Molarity. Meaning that you multiply 3 x .25 and get .75 moles. 58.443g/molNaCl x .75 moles = FINAL ANSWER 43.83225g NaCl, Sig Fig, 43.83gNaCl