Question

What is the molar mass of a compound that contains 39.98% C, 10.06% H, 26.63% O, and 23.31% N and 2 empirical units? report your answer in grams/mole to two (2) decimal places. Circle final answer.

Answer 1

we have mass of each elements as:

C: 39.98 g

H: 10.06 g

N: 23.31 g

O: 26.63 g

Divide by molar mass to get number of moles of each:

C: 39.98/12.01 = 3.3289

H: 10.06/1.008 = 9.9802

N: 23.31/14.01 = 1.6638

O: 26.63/16.0 = 1.6644

Divide by smallest to get simplest whole number ratio:

C: 3.3289/1.6638 = 2

H: 9.9802/1.6638 = 6

N: 1.6638/1.6638 = 1

O: 1.6644/1.6638 = 1

So empirical formula is:C₂H₆NO

Since there are 2 empirical unit,

molecular formula is:

C4H12N2O2

  

Molar mass of C4H12N2O2 = 4*MM(C) + 12*MM(H) + 2*MM(N) + 2*MM(O)
= 4*12.01 + 12*1.008 + 2*14.01 + 2*16.0
= 120.6 g/mol


Answer: 120.6 g/mol