## Problem F5 (7th Edition)

105085381
Posts: 44
Joined: Fri Sep 28, 2018 12:15 am

### Problem F5 (7th Edition)

Problem F5 asks for the mass percentage composition of L-carnitine, C7H15NO3, a compound taken as a dietary supplement to reduce muscle fatigue.

My first step was to take each element and multiple its' coefficient by its' molar mass:
7C --> 7(12.01) = 84.07
15H --> 15(1.01) = 15.15
1N --> 1(14.007) = 14.007
3O --> 3(15.999) = 47.997

I then added up all of these outcomes to get the total molar mass of the whole compound = 161.224 g

My next step was to divide the molar mass of each element by the molar mass of the whole compound and multiple by 100 to get % composition for each element:
84.07/161.224 * 100% = 52.14% C
15.15/161.224 * 100% = 9.4% H
14.007/161.224 * 100% = 8.69% N
47.997/161.224 * 100% = 29.77% O

These values were my final results for mass percentage composition of each element in L-carnitine ... am I missing a final step or are these percentages my final solution?

Amy Lefley 1J
Posts: 60
Joined: Fri Sep 28, 2018 12:15 am

### Re: Problem F5 (7th Edition)

When finding mass composition of a compound the main steps are to:
1. find the molar mass of the entire compound
2. find the molar mass of each element within the compound
3. divide the molar mass of each element you found in step 2 by the molar mass you found in step 1 and multiply these values by 100 to get your percents

Yejin Ban
Posts: 6
Joined: Thu Jul 25, 2019 12:17 am

### Re: Problem F5 (7th Edition)

At first I wasn't sure if I had my final answer when I got the percentages of each element, but they are they final answer. The formula to finding mass percentage of an element in a compound is (mass of atom/matter weight)x100%. Depending on how many of each element is present, you would multiply that number to the molar mass of the element found on the periodic table and divide by the total matter weight.

JustinHorriat_3b
Posts: 54
Joined: Wed Sep 18, 2019 12:19 am

### Re: Problem F5 (7th Edition)

Yes those numbers look right, and the steps that amy gave were really good too. An extra tip that I would give u is that just to make sure you mass percentages are correct, add all them up and they should add to 100%, if not you did something wrong.