Question

question 9
1 pts
a compound has the following percent composition: carbon 49.48%, hydrogen 5.19%, oxygen 16.48% and nitrogen 28.85%. its molecular weight is 194.19 amu. what is its molecular formula?
c₆h₁₂no₆
c₈h₁₀n₄o₂
c₆h₆n₂o
c₄h₃n₂o

Explanation:

Step1: Calculate moles of each element

Assume 100g of the compound.
Moles of \(C=\frac{49.48g}{12.01g/mol}\approx4.12\)
Moles of \(H=\frac{5.19g}{1.008g/mol}\approx5.15\)
Moles of \(O=\frac{16.48g}{16.00g/mol}\approx1.03\)
Moles of \(N=\frac{28.85g}{14.01g/mol}\approx2.06\)

Step2: Find the ratio of moles

Divide each by the smallest number (1.03)
Ratio \(C=\frac{4.12}{1.03}\approx4\)
Ratio \(H=\frac{5.15}{1.03}\approx5\)
Ratio \(O=\frac{1.03}{1.03} = 1\)
Ratio \(N=\frac{2.06}{1.03}=2\)
Empirical formula is \(C_4H_5N_2O\)

Step3: Calculate empirical formula weight

\(M_{empirical}=(4\times12.01)+(5\times1.008)+(2\times14.01)+(1\times16.00)=97.09g/mol\)

Step4: Find the multiple \(n\)

\(n=\frac{194.19}{97.09}\approx2\)

Step5: Determine molecular formula

Multiply empirical formula by \(n = 2\)
\(C_{4\times2}H_{5\times2}N_{2\times2}O_{1\times2}=C_8H_{10}N_4O_2\)

Answer:

\(C_8H_{10}N_4O_2\) (the second option)