Call Now to Set Up Tutoring:

(888) 888-0446

College Chemistry : Combustion Reactions

Study concepts, example questions & explanations for College Chemistry

Create An Account

All College Chemistry Resources

1 Diagnostic Test 100 Practice Tests Question of the Day Flashcards Learn by Concept

Example Questions

Example Question #1 : Reactions

Suppose that the only elements a compound contains are carbon, hydrogen, and oxygen. If complete combustion of $70.86\:g$ $\displaystyle 70.86\:g$ of this compound produces $103.9\:g$ $\displaystyle 103.9\:g$ of $CO_{2}$ $\displaystyle CO_{2}$ and $42.52\:g$ $\displaystyle 42.52\:g$ of $H_{2}O$ $\displaystyle H_{2}O$, what is this compound's molecular formula?

Note: The molecular weight of this compound is $120.104\:\frac{g}{mol}$ $\displaystyle 120.104\:\frac{g}{mol}$.

Possible Answers:

$C_{5}H_{12}O_{3}$ $\displaystyle C_{5}H_{12}O_{3}$

$C_{3}H_{4}O_{5}$ $\displaystyle C_{3}H_{4}O_{5}$

$C_{4}H_{8}O_{4}$ $\displaystyle C_{4}H_{8}O_{4}$

$C_{7}H_{4}O_{2}$ $\displaystyle C_{7}H_{4}O_{2}$

Correct answer:

$C_{4}H_{8}O_{4}$ $\displaystyle C_{4}H_{8}O_{4}$

Explanation:

To answer this question, it's important to remember the details of combustion reactions. In the presence of oxygen and a sufficient amount of energy to initiate the process, combustion reactions that go to completion will result in the complete oxidation and breakdown of the initial reactant.

The $CO_{2}$ $\displaystyle CO_{2}$ produced from the reaction contains all of the carbon in the original reactant. Likewise, the $H_{2}O$ $\displaystyle H_{2}O$ produced contains all the hydrogen in the original compound. The oxygen content in the original compound is everything left over.

The first step then is to use the mass of each product to find the mass of each element in the original compound. To do this, we'll need to use the molar mass for each of the products as well as the individual elements.

$103.9\:g\:CO_{2}\cdot \frac{12\:\frac{g}{mol}\:C}{44\:\frac{g}{mol}\:CO_{2}}=28.34\:g\:C$ $\displaystyle 103.9\:g\:CO_{2}\cdot \frac{12\:\frac{g}{mol}\:C}{44\:\frac{g}{mol}\:CO_{2}}=28.34\:g\:C$

$42.52\:g\:H_{2}O\cdot \frac{2\:\frac{g}{mol}\:H}{18\:\frac{g}{mol}\:H_{2}O}=4.72\:g\:H$ $\displaystyle 42.52\:g\:H_{2}O\cdot \frac{2\:\frac{g}{mol}\:H}{18\:\frac{g}{mol}\:H_{2}O}=4.72\:g\:H$

The combined mass of carbon and hydrogen in the original compound is $28.34\:g+4.72\:g=33.06\:g$ $\displaystyle 28.34\:g+4.72\:g=33.06\:g$.

The remaining mass will come from oxygen. Thus, the original compound will contain $70.86\:g-33.06\:g=37.8\:g$ $\displaystyle 70.86\:g-33.06\:g=37.8\:g$ of oxygen.

Once we have the mass of each element, we can use that information to calculate the number of moles of each element in the original compound.

$28.34\:g\:C\cdot\frac{1\:mol\:C}{12\:g\:C}=2.36\:mol\:C$ $\displaystyle 28.34\:g\:C\cdot\frac{1\:mol\:C}{12\:g\:C}=2.36\:mol\:C$

$4.72\:g\:H\cdot\frac{1\:mol\:H}{1\:g\:H}=4.72\:mol\:H$ $\displaystyle 4.72\:g\:H\cdot\frac{1\:mol\:H}{1\:g\:H}=4.72\:mol\:H$

$37.8\:g\:O\cdot \frac{1\:mol\:O}{16\:g\:O}=2.36\:mol\:O$ $\displaystyle 37.8\:g\:O\cdot \frac{1\:mol\:O}{16\:g\:O}=2.36\:mol\:O$

Now that we have the relative molar amounts of each element in the original compound, we can find the empirical formula by finding the smallest whole number ratios.

$C_{2.36}H_{4.72}O_{2.36}=CH_{2}O$ $\displaystyle C_{2.36}H_{4.72}O_{2.36}=CH_{2}O$

From this, we can conclude that the empirical mass of the compound is $30\:g$ $\displaystyle 30\:g$.

Finally, since we are given the compound's molecular weight, we can use that information to find the molecular formula for the compound.

$\frac{120.104}{30}\approx4$ $\displaystyle \frac{120.104}{30}\approx4$

$4(CH_{2}O)=C_{4}H_{8}O_{4}$ $\displaystyle 4(CH_{2}O)=C_{4}H_{8}O_{4}$

Report an Error

View Tutors

Mayowa
Certified Tutor

Logan University, Bachelor of Science, Biology, General.

View Tutors

Laura
Certified Tutor

New York University, Bachelor in Arts, Drama and Dance Teacher Education.

View Tutors

Rachel
Certified Tutor

University of Arkansas at Little Rock, Bachelor in Arts, Mathematics.

All College Chemistry Resources

1 Diagnostic Test 100 Practice Tests Question of the Day Flashcards Learn by Concept

Popular Subjects

ACT Tutors in Washington DC, LSAT Tutors in Washington DC, SAT Tutors in Dallas Fort Worth, Biology Tutors in Seattle, LSAT Tutors in San Diego, Statistics Tutors in Miami, Math Tutors in Los Angeles, LSAT Tutors in San Francisco-Bay Area, Reading Tutors in Atlanta, Reading Tutors in Miami

Popular Courses & Classes

LSAT Courses & Classes in Phoenix, SAT Courses & Classes in Miami, SAT Courses & Classes in Denver, ACT Courses & Classes in Phoenix, GRE Courses & Classes in Atlanta, SSAT Courses & Classes in Washington DC, GMAT Courses & Classes in San Diego, SAT Courses & Classes in New York City, GRE Courses & Classes in Phoenix, Spanish Courses & Classes in Seattle

Popular Test Prep

SAT Test Prep in Boston, LSAT Test Prep in Chicago, MCAT Test Prep in Washington DC, GRE Test Prep in Atlanta, GMAT Test Prep in Philadelphia, GMAT Test Prep in San Diego, ACT Test Prep in Miami, ACT Test Prep in Dallas Fort Worth, GRE Test Prep in Seattle, GMAT Test Prep in Boston

DMCA Complaint

If you believe that content available by means of the Website (as defined in our Terms of Service) infringes one or more of your copyrights, please notify us by providing a written notice (“Infringement Notice”) containing the information described below to the designated agent listed below. If Varsity Tutors takes action in response to an Infringement Notice, it will make a good faith attempt to contact the party that made such content available by means of the most recent email address, if any, provided by such party to Varsity Tutors.

Your Infringement Notice may be forwarded to the party that made the content available or to third parties such as ChillingEffects.org.

Please be advised that you will be liable for damages (including costs and attorneys’ fees) if you materially misrepresent that a product or activity is infringing your copyrights. Thus, if you are not sure content located on or linked-to by the Website infringes your copyright, you should consider first contacting an attorney.

Please follow these steps to file a notice:

You must include the following:

A physical or electronic signature of the copyright owner or a person authorized to act on their behalf; An identification of the copyright claimed to have been infringed; A description of the nature and exact location of the content that you claim to infringe your copyright, in \ sufficient detail to permit Varsity Tutors to find and positively identify that content; for example we require a link to the specific question (not just the name of the question) that contains the content and a description of which specific portion of the question – an image, a link, the text, etc – your complaint refers to; Your name, address, telephone number and email address; and A statement by you: (a) that you believe in good faith that the use of the content that you claim to infringe your copyright is not authorized by law, or by the copyright owner or such owner’s agent; (b) that all of the information contained in your Infringement Notice is accurate, and (c) under penalty of perjury, that you are either the copyright owner or a person authorized to act on their behalf.

Send your complaint to our designated agent at:

Charles Cohn Varsity Tutors LLC
101 S. Hanley Rd, Suite 300
St. Louis, MO 63105

Or fill out the form below:

Do not fill in this field

Contact Information

* Full legal name

Company name

* Phone number

* Email address

Address

* Address1

Address2

* City

* State

* Zipcode

* Country

Complaint Details

* URL of copyrighted work (where your original material is located)

* Please describe the copyrighted work so that it may be easily identified

I am the owner, or an agent authorized to act on behalf of the owner of an exclusive right that is allegedly infringed.

I have a good faith belief that the use of the material in the manner complained of is not authorized by the copyright owner, its agent, or the law.

This notification is accurate.

I acknowledge that there may be adverse legal consequences for making false or bad faith allegations of copyright infringement by using this process.

* Signature (your digital signature is legally binding)

HIGH SCHOOL

GRADUATE SCHOOL

K-8

Search 50+ Tests

math tutoring

science tutoring

foreign languages

elementary tutoring

other

Search 350+ Subjects

College Chemistry : Combustion Reactions

Study concepts, example questions & explanations for College Chemistry

All College Chemistry Resources

Example Questions

Example Question #1 : Reactions

All College Chemistry Resources

Report an issue with this question

DMCA Complaint

Contact Information

Address

Complaint Details

Email address:
Your name:
Feedback: