Question

Find the percent composition of a compound containing sodium and chlorine if 24.34g of the compound contains 13.45g of sodium.

My work:
Molar mass of NaCl: MNa +MCl
= 22.99 g/mol + 35.45 g/mol
= 58.44 g/mol

Percent composition of Na:
22.99 g/mol / 58.44 g/mol x 100
= 39.34% Na

Percent composition of Cl:
35.45 g/mol / 58.44 x 100
= 60.66% Cl

This is where I get stuck. How do the 24.34g and 13.45g come into play?

Answer 1

you are on a goose chase.

percent Na=13.45/24.34= 55 percent
percent Cl=10.89/24.34=44.7 percent

Answer 2

I'm glad you asked that question. All of the work you have done is exactly right BUT you haven't worked the problem. You worked a similar problem but not the one stated.
% Na FROM THE DATA IN THE PROBLEM is
(g Na/total g)*100 = (13.45/24.34)*100 = 55.26%
Then % Cl = 100%-55.25 = ?

You assumed the formula is NaCl with your work; the problem doesn't tell you the formula but gives the data to calculate percent.
In fact I took the data given and it gives a formula very close to Na2Cl. Read the problem again and notice it says a compound containing Na and Cl but it never gives the formula. Your prof just made up a problem.

Answer 3

Thank you guys so much for helping me! I see my steps were really unnecessary.