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?

1 Answer
Dec 22, 2017

Answer:

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

Explanation:

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