×
Log in to StudySoup
Get Full Access to Chemistry - Textbook Survival Guide
Join StudySoup for FREE
Get Full Access to Chemistry - Textbook Survival Guide

Determining a Molecular Formula Mesitylene, a hydrocarbon

Chemistry: A Molecular Approach | 3rd Edition | ISBN: 9780321809247 | Authors: Nivaldo J. Tro ISBN: 9780321809247 1

Solution for problem 1PE Chapter 3.14SE

Chemistry: A Molecular Approach | 3rd Edition

  • Textbook Solutions
  • 2901 Step-by-step solutions solved by professors and subject experts
  • Get 24/7 help from StudySoup virtual teaching assistants
Chemistry: A Molecular Approach | 3rd Edition | ISBN: 9780321809247 | Authors: Nivaldo J. Tro

Chemistry: A Molecular Approach | 3rd Edition

4 5 0 324 Reviews
27
0
Problem 1PE

Determining a Molecular Formula Mesitylene, a hydrocarbon found in crude oil, has an empirical formula of C3H4 and an experimentally determined molecular weight of 121 amu. What is its molecular formula? Cyclohexane, a commonly used organic solvent, is 85.6% C and 14.4% H by mass with a molar mass of 84.2 g/mol. What is its molecular formula? (a) C6H (b) CH2 (c) C5H24 (d) C6H12 (e) C4H8.

Step-by-Step Solution:

Answer: Step 1 Mesitylene or 1,3,5-trimethylbenzene is a derivative of benzene with three methyl substituents positioned symmetrically around the ring. The other two isomeric trimethylbenzenes are 1,2,4-trimethylbenzene (pseudocumene) and 1,2,3-trimethylbenzene (hemi melitene). All three compounds have the formula C H (CH 6 3whic3 3commonly abbreviated C H Me . Mesityle6 3 3 is a colourless liquid with sweet aromatic odor. It is a component of coal tar, which is its traditional source. It is a precursor to diverse fine chemicals. The mesityl group (Mes) is a substituent with the formula C H Me and is found in various other compounds. 6 2 3 Step 2 To know the molecular formula of a compound we have to know the empirical formula of a compound. We are given an empirical formula and a molecular weight of a compound and asked to determine its molecular formula. Step 3 The subscripts in a compound’s molecular formula are whole-number multiples of the subscripts in its empirical formula. We find the appropriate multiple by using Equation Whole-number multiple = molecular weight/ empirical formula weight. The formula weight of the empirical formula C3H4 is 3112.0 amu 2+411.0 amu2 = 40.0 amu Whole-number multiple = molecular weight/ empirical formula weight = 121 40.0 = 3.03 Step 4 Only whole-number ratios make physical sense because molecules contain whole atoms. The 3.03 in this case could result from a small experimental error in the molecular weight. We therefore multiply each subscript in the empirical formula by 3 to give the molecular formula: C9H12. Check We can have confidence in the result because dividing molecular weight by empirical formula weight yields nearly a whole number. Step 5 Combustion analysis can only determine the empirical formula of a compound; it cannot determine the molecular formula. However, other techniques can determine the molecular weight. Once we know this value, coupled with the empirical formulas, we can easily calculate what the molecular formula is.

Step 6 of 9

Chapter 3.14SE, Problem 1PE is Solved
Step 7 of 9

Textbook: Chemistry: A Molecular Approach
Edition: 3
Author: Nivaldo J. Tro
ISBN: 9780321809247

Unlock Textbook Solution

Enter your email below to unlock your verified solution to:

Determining a Molecular Formula Mesitylene, a hydrocarbon

×
Log in to StudySoup
Get Full Access to Chemistry - Textbook Survival Guide
Join StudySoup for FREE
Get Full Access to Chemistry - Textbook Survival Guide
×
Reset your password