How many grams of NaCl should be added to 250 grams of water to make 0.40 msolution?

Hello.

This is very similar to problem #9 in a homework assignment hosted by
uchsc.edu:
"9.
Molarity is defined as (number of moles of solute)/(number of liters
of solvent) and is expressed using the symbol M.
NaCl... MW= 23 + 35.45 = 58.45 Daltons
58.45g per mole"
source: BIO 5099 Homework, hosted by uchsc.edu, cached by Google:
http://216.239.53.104/search?q=cache:eviA9v1Fm5AJ:compbio.uchsc.edu/Hunter/bio5099/homework/hw4sol.pdf+&hl=en&ie=UTF-8

First we convert grams of water to liters.  1 liter of water is
equivalent to 1000 grams, so:
250 grams of water is 0.250 liters 


X moles NaCl 
------------ = 0.40 molarity solution
0.250 litres

Using algebra, we determine that X = 0.10 moles NaCl


Thus, since the molar mass of NaCl = 58.45 g....

Y grams NaCl (1 mole NaCl) 
-------------------------- = 0.10 moles NaCl
    58.45 grams


Using algebra, we determine that Y = 5.845 grams NaCl.

Thus, that the answer is 5.845 grams NaCl.

search strategy: nacl, water, moles, solute  

I hope this helps.