Calculate the molarity

  • Thread starter DB
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  • #1
DB
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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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  • #2
dextercioby
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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.
 
  • #3
DB
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~0.357 mol/L?
 
  • #4
dextercioby
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What is the value of "x" that u found...?

Daniel.
 
  • #5
DB
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i got ~0.51 moles by dividing 29.25 by 56.5, the i cross multiplied knowing x.
 
  • #6
dextercioby
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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.
 
  • #7
DB
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O i was so hooked on dilution! is the answer ~0.72 mol/L???
 
  • #8
dextercioby
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Yes,pretty much so.

Daniel.
 

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