A sample of a compound contains 7.89 g potassium, 2.42 g carbon, and 9.69 g oxygen. What is the empirical and molecular formulas of this compound, which has a molar mass of 198.22 g/mol?

Question

17556 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2017-12-22T11:04:55

The empirical formula is $KCO_3$ . The molecular formula is $K_2C_2O_6$

Let the molecular formula be $K_mC_nO_p$

The weight of the sample is

$m=7.89+2.42+9.69=20g$

The number of moles of each element is

Potassium $=7.89/39.1=0.2$

Carbon $=2.42/12=0.2$

Oxygen $=9.69/16=0.6$

Divide by $0.2$

Potassium $=0.2/0.2=1$

Carbon $=0.2/0.2=1$

Oxygen $=0.6/0.2=3$

Therefore,

The empirial formula is $KCO_3$

Since the molar mass is $=198.22$

and

$M_K+M_C+M_O=39+12+3*16=99$

The molecular formula is $K_2C_2O_6$

And the name of this compound is probably

Potassium peroxydicarbonate