how manygrams of NaCl should be added to 250 grams of water to make a 0.40 m solution?

Question

What do meters have to do with this problem???

Answer 1

x = 0.4 (250 + x )
x = 100 + 0.40 x
0.60 x = 100
x = 166.666 grams

Answer 2

When talking about the concentration of a solution, M means molarity, or moles of solute per liters of solution. m (not capital) means molality, or moles of solute per kilograms of solvent (water, or whatever you put the solute in). The m doesn't have anything to do with meters.

The equation for molarity is M= mol/L
So the equation here is 0.4 M= x mol/0.25 L. We know that there are 0.25 L because to convert grams of water to milliliters, you multiply by 1 because the density of water is 1 gram/milliliter. So you have 250 milliliters, or 0.25 L.

When you multiply 0.4 by 0.25, you get 0.1 mol NaCl. When you multiply this by the molar mass (58.5 grams/mol), you get 5.85 grams.

Whether the m was capital or not (molarity or molality), you still get the same answer.

Answer 3

M(molarity) refers to concentration, usually in mol/dm^3.
We assume density of H2O to be 1.0g/cm^3.
No of moles of NaCl = 250/1000 x 0.4 = 0.10 moles
mass = n x Mr
= 0.10 x (23.1 + 35.5)
= 5.86g
(n --- no. of moles Mr --- Relative formula mass

Answer 4

a molar solution of Nacl corresponds to 58.5g/L
250g = 0.25L
so molar = 58.5*0.25
and to have 0.4M
you need 58.5*0.25*0.4 =5.85g NaCl

Answer 5

ans = 5.85 grams of NaCl...0.4mol/1.0L = n mol/0.25L,....solving for n we get n = 0.1 mol of NaCl...0.1mol of NaCl * 58.5 gram/mol = 5.85 gram NaCl