# Calculate the molarity

Havin a little trouble:
Calculate the molarity of 29.25 g of NaCl dissolved in 700ml of total solution in moles per litre.

I know that 1 mol of salt is 57 g so 29.25 g of salt is ~0.51 mol...
But then what?
Is the answer ~0.35 mol/700L ? I cross multiplied.

Thanks

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dextercioby
Homework Helper
No.The molar mass of NaCl is 56.5.You'll have to figure out how many moles that means and then apply the simple rule:
x moles------------>700mL
y moles------------>1000mL

Daniel.

P.S."y" is the one you're interested in.

~0.357 mol/L?

dextercioby
Homework Helper
What is the value of "x" that u found...?

Daniel.

i got ~0.51 moles by dividing 29.25 by 56.5, the i cross multiplied knowing x.

dextercioby
Homework Helper
And u wound up with ~0.36,huh...?You didn't do it (the cross multiplication) correctly,after all,at constant concentration,the more sollution u have (1000mL cf.700mL),the more dilluted substance u must have,right??

Daniel.

O i was so hooked on dilution! is the answer ~0.72 mol/L???

dextercioby