how many grams of NaCl would you need to prepare 500.0 ml of a 2.5x10^-2 M solution of NaCl

Question

The answer i have gotten is 0.73g I just want to confirm it

thanks

Answer 1

Yes , your answer is correct.

use molarity equation :

M= moles / volume in Liters

 

volume must in L so convert 500 ml to L then switch all the datas in the molarity equation 

2.5 x 10^-2 = moles/ .5 

moles = 1.25x19^-2

convert this to grams using the Molar mass of NaCl by multiply the moles you found above with the molar mass of NaCl

Answer 2

Using the equation for Molarity to find moles:

 

Molarity = mol/Liters

 

mol = Molarity * Liters

 

And then using the molar mass of NaCl to cancel out moles out of our units and to get grams:

 

NaCl = 58.44grams/mol

 

grams = (grams/mol)(mol)

grams = (molar mass of NaCl) *(Molarity * Liters)

 

we get:

 

grams = (58.44 g/mol)* (2.5x10^-2 molarity * 0.500 liters)

grams = 0.7305 grams

 

And applying significant figures we get 0.73 grams of NaCl. So you are correct.