Question

PLEASE HELP!!

Empirical and Molecular Formulas
Phencyclidine (“angel dust”) is C17H25N. A sample suspected of being this dangerous drug was found to have a percentage composition of 83.71% C, 10.42% H, and 5.61% N. Do these data acceptably match the theoretical data for phencyclidine? (Calculate percentages to four significant figures.)

Answer 1

To determine whether the given percentage composition matches the theoretical composition of phencyclidine, we need to calculate the theoretical percentage composition of C, H, and N in phencyclidine and compare it with the given values.

The molar mass of phencyclidine (C17H25N) can be calculated as:

Molar mass = (17 x atomic mass of C) + (25 x atomic mass of H) + (1 x atomic mass of N)

= (17 x 12.011) + (25 x 1.008) + (1 x 14.007)

= 243.349 g/mol

The theoretical percentage composition of C, H, and N in phencyclidine can be calculated as follows:

Percentage of C = (17 x atomic mass of C x 100) / molar mass

= (17 x 12.011 x 100) / 243.349

= 83.54%

Percentage of H = (25 x atomic mass of H x 100) / molar mass

= (25 x 1.008 x 100) / 243.349

= 10.36%

Percentage of N = (1 x atomic mass of N x 100) / molar mass

= (1 x 14.007 x 100) / 243.349

= 5.10%

Therefore, the theoretical percentage composition of C, H, and N in phencyclidine is 83.54%, 10.36%, and 5.10%, respectively.

Comparing the theoretical and given percentage compositions, we can see that the values are very close. The given percentage composition of 83.71% C, 10.42% H, and 5.61% N are within acceptable limits of the theoretical values. Therefore, we can conclude that the sample is consistent with phencyclidine.

Note: small differences between the theoretical and experimental values can occur due to experimental errors and uncertainties.