An unknown compound was found to have a percent composition as follows 47.0% potassium, 14.5% carbon, and 38.5% oxygen. What is its empirical formula?

1 Answer
anor277
Jan 2, 2016

Potassium oxalate?

Explanation:

In 100 g of compound there are 47.0 g potassium, 14.5 g carbon, and 38.5 g oxygen. Why?

We divide thru by the atomic masses:

#K# #=# #(47.0*g)/(39.1*g*mol^(-1))# #=# #1.20#.

#C# #=# #(14.5*g)/(12.0*g*mol^(-1))# #=# #1.21#.

#O# #=# #(38.5*g)/(16.0*g*mol^(-1))# #=# #2.4#.

Now if we divide thru by the lowest ratio, we get #K_nC_mO_o# #=# #KCO_2# as the empirical formula.

You have likely got the dipotassium salt of oxalic acid, #HOC(=O)C(=O)OH#, which has precisely this empirical formula. I take it you are an undergraduate?

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