### G.5

Posted: **Sun Apr 08, 2018 1:33 pm**

by **Fiona Grant 1I**

I am still a bit confused as to the setup of this problem. How do you find the molarity of the Na2CO3 solution using the mass and volume given? I know that n=m/M and c=n/V, but I don't understand how to find the concentration using these equations.

### Re: G.5 [ENDORSED]

Posted: **Sun Apr 08, 2018 1:35 pm**

by **Natalie Noble 1G**

Molarity = moles/volume

You are given 2.111g Na2Co3 but to put it in the formula above you need to find how many moles there are of Na2Co3

N = m/M or

Moles = mass/molar mass

105.99g/mol is the molar mass of Na2Co3

Moles = (2.111g) / ( 105.99g/mol)

Moles = .0199 mol

Now you have the moles of Na2Co3, and the problem gave you the volume of the solution (250ml) but since molarity is mol/L convert 250ml in L, which becomes .250L

Molarity = moles/volume

Molarity = .0199 mol / .250L

Molarity = .07967M