Question

find the empirical formula.
an addictive substance being analyzed in the lab has a molar mass of is 162.23 g/mol. a 100 gram sample contains 74.0% carbon, 8.7% hydrogen, and 17.3% nitrogen. what would this substances empirical formula be?
composition by % mass
empirical formula
weight = ? amu
c h n

Explanation:

Step1: Calculate moles of each element

Assume 100g sample.
Moles of \(C=\frac{74.0g}{12.01g/mol}\approx6.16mol\)
Moles of \(H=\frac{8.7g}{1.008g/mol}\approx8.63mol\)
Moles of \(N=\frac{17.3g}{14.01g/mol}\approx1.23mol\)

Step2: Divide by the smallest mole value

Divide moles of \(C\), \(H\), \(N\) by \(1.23\)
\(C:\frac{6.16}{1.23}\approx5\)
\(H:\frac{8.63}{1.23}\approx7\)
\(N:\frac{1.23}{1.23} = 1\)

Answer:

\(C_5H_7N\)