Question

The low-resolution mass spectrum of an unknown analgesic X had a molecular ion of 151. Possible molecular formulas include C7H5NO3, C8H9NO2, and C10H17N. High-resolution mass spectrometry gave an exact mass of 151.0640. What is the molecular formula of X?

Answer 1

Answer:

The molecular formula of X is C8H9NO2

Explanation:

Step 1: Data given

exact mass of 151.0640

Molar mass of C = 12 g/mol

Molar mass of H = 1.00783 g/mol

Molar mass of O = 15.9949 g/mol

Molar mass of N = 14.0031 g/mol

Step 2: Calculate molar mass of C7H5NO3

7*12 + 5*1.00783 + 14.0031 + 3*15.9949 = 151.02695 g/mol

Step 3: Calculate molar mass of C8H9NO2

8*12 + 9*1.00783 + 14.0031 + 2*15.9949 = 151.06337 g/mol

Step 4: Calculate molar mass of C10H17N

10*12 + 17*1.00783 + 14.0031 = 151.13621 g/mol

The molecular formula of X is C8H9NO2