What is the molar concentration of ethanol in a solution made by mixing 23g of ethanol with 200ml of water?

Question

density of ethanol = .789g/mL

MW ethanol = 46g/mol

Answer 1

I think you have half of a mole of ethanol. Then you divide that by liters of solution which is .2L which gives you 2.5 as the molarity. I'm not sure though.  

Answer 2

molarity = number of moles in TOTAL volume of solution

M = moles/L

moles of Ethanol = mass / molecular weight

= 23 g / 46 g/mol

= 0.5 moles

The volume of the solution = volume of water + volume of ethanol added

The density of ethanol is 0.789 g/ml

So the volume of ethanol added = 23 g x 0.789 g/ml

= 18.147 ml

therefore the total volume of solution = 18.147 + 200 ml

= 218.147 ml

= 0.218 L

Now

Molarity = moles / L

= 0.5 mol / 0.218 L

= 2.29 M

or 2.3 M (2 sig figs)