Question

Compound Y has the elements C, H, N and O. It's exact mass is 91.0425. Answer the following questions. Isotope Exact Mass 1H 1.008 12C 12.000 14N 14.003 16O 15.995 How many carbons does compound Y have? Write the numerical symbol for your answer. How many hydrogens does compound Y have? Write the numerical symbol for your answer. How many nitrogens does compound Y have? Write the numerical symbol for your answer. How many oxygenns does compound Y have? Write the numerical symbol for your answer.

Answer 1

Answer:

Six C atoms (C₆); five H atoms (H₅); one N atom (N); no O atoms

Explanation:

The rule of 13 states that the formula of a compound is a multiple n of 13 (the molar mass of CH) plus a remainder r.

MF = CₙHₙ₊ᵣ

Y has a molecular mass of 91 u

91/13 =7r0

The formula can't be C₇H₇ because a hydrocarbon must have an even number of H atoms,

The odd mass and the odd number of H atoms make it reasonable to add an N atom and subtract CH₂ (CH₂ = 14):

C₇H₇ + N - CH₂ = C₆H₅N

Check:

6C = 6 × 12.000 = 72.000 u

5H = 5 ×   1.008 =   5.040

1N =  1 × 14.003 =  14.003    

             TOTAL =   91.043 u

This is excellent agreement with the observed mass of 91.0425 u.

There are six  C atoms (C₆)

There are five H atoms (H₅)

There is    one N atom   (N)

There are no   O atoms.