Call Now to Set Up Tutoring:

(888) 888-0446

High School Chemistry : Help with Enthalpy

Study concepts, example questions & explanations for High School Chemistry

Create An Account

All High School Chemistry Resources

6 Diagnostic Tests 143 Practice Tests Question of the Day Flashcards Learn by Concept

Example Questions

Example Question #2 : Thermochemistry And Energetics

Consider the following balanced reaction:

$2C_{(s)} + 3H_{2}_{(g)} \rightarrow C_{2}H_{6}_{(g)}$

$\Delta H = -84kJ$

What is the change in enthalpy if $\small 10g$ of solid carbon is used in the above reaction?

Possible Answers:

-35kJ

35kJ

-420kJ

-70kJ

Correct answer:

-35kJ

Explanation:

The enthalpy of -84kJ describes the amount of heat when the amount of carbon in the balanced reaction (two moles) is used. Since only $\small 10g$ of carbon are used, we can find how much heat is released.

When two moles of carbon are used, -84kJ are released. Two moles of carbon is equal to $\small 24g$ of carbon, based on carbon's atomic mass.

$2mol\ C*\frac{12g\ C}{1mol\ C}=24g\ C$

Knowing this, we can set up proportions in order to determine how much heat is released by $\small 10g$ of carbon.

$10g\ C*\frac{-84kJ}{24g\ C}=-35kJ$

So $\small 10g$ of carbon results in -35kJ of heat being released to the surroundings.

Report an Error

Example Question #11 : Thermochemistry And Energetics

Consider these two half reactions:

Step 1. $CH_{4}_{(g)} + 2O_{2}_{(g)} \rightarrow CO_{2}_{(g)} + 2H_{2}O_{(l)}$ $\Delta H = -890kJ$

Step 2. $H_{2}O_{(l)} \rightarrow H_{2}O_{(g)}$ $\Delta H = 44kJ$

Based on these half reactions, find the enthalpy for the following reaction:

$CH_{4}_{(g)} + 2O_{2}_{(g)} \rightarrow CO_{2}_{(g)} + 2H_{2}O_{(g)}$

Possible Answers:

-934kJ

-846kJ

-978kJ

-802kJ

Correct answer:

-802kJ

Explanation:

Hess's law states that the enthalpy of the total reaction is equal to the enthalpy of the steps required to get to the total reaction, regardless of the path that is chosen. This means that we can combine the two half steps with known enthalpies in order to solve for the enthalpy of the main reaction.

Step 1. $CH_{4}_{(g)} + 2O_{2}_{(g)} \rightarrow CO_{2}_{(g)} + 2H_{2}O_{(l)}$ $\Delta H = -890kJ$

Step 2. $H_{2}O_{(l)} \rightarrow H_{2}O_{(g)}$ $\Delta H = 44kJ$

Total: $CH_{4}_{(g)} + 2O_{2}_{(g)} \rightarrow CO_{2}_{(g)} + 2H_{2}O_{(g)}$

Since step 1 results in two moles of liquid water, we need to use the second step twice in order to replace them with two moles of water vapor.

Combined: $CH_{4(g)}+2O_{2(g)}+2H_2O_{(l)} \rightarrow CO_{2(g)}+2H_2O_{(l)}+2H_2O_{(g)}$

Since the total reaction is created by step 1 occurring once and step 2 occurring twice, we can write the enthalpy as:

$\Delta H_{total } = \Delta H_{1} + 2\Delta H_{2}$

Use the given enthalpies of the steps to calculate the total change in enthalpy.

$\Delta H_{total} = -890kJ + 2(44kJ)$

$\Delta H_{total} = -802kJ$

Report an Error

Example Question #2 : Help With Enthalpy

How much energy is required to heat 35g of H_2O from $35^\circ C$ to $85^\circ C$ ?

Possible Answers:

5.5kJ

7.3kJ

7300kJ

11.2kJ

50J

Correct answer:

7.3kJ

Explanation:

Use the following formula:

$\Delta H =mc \Delta T$

Plug in values:

$\Delta H =35*4.18(85-35)$

$\Delta H =7.3kJ$

Report an Error

View Tutors

Justin
Certified Tutor

University of Toledo, Bachelors, Environmental Science. University of Michigan, Masters, Natural Resource Management.

View Tutors

Andrew
Certified Tutor

The University of Kansas, Bachelor of Science, Biochemistry.

View Tutors

Mr. Henderson
Certified Tutor

Swarthmore College, Bachelor of Science, Engineering. MBU, Master of Science, Education.

All High School Chemistry Resources

6 Diagnostic Tests 143 Practice Tests Question of the Day Flashcards Learn by Concept

Popular Subjects

SSAT Tutors in Seattle, SSAT Tutors in San Francisco-Bay Area, Spanish Tutors in Houston, Reading Tutors in Philadelphia, Chemistry Tutors in Houston, Computer Science Tutors in Washington DC, LSAT Tutors in Washington DC, MCAT Tutors in Seattle, Chemistry Tutors in San Diego, Math Tutors in Dallas Fort Worth

Popular Courses & Classes

SAT Courses & Classes in Dallas Fort Worth, SAT Courses & Classes in Chicago, GRE Courses & Classes in Philadelphia, GMAT Courses & Classes in San Francisco-Bay Area, LSAT Courses & Classes in Philadelphia, ACT Courses & Classes in New York City, MCAT Courses & Classes in Washington DC, SSAT Courses & Classes in Dallas Fort Worth, LSAT Courses & Classes in Atlanta, Spanish Courses & Classes in Miami

Popular Test Prep

ACT Test Prep in New York City, SSAT Test Prep in Boston, LSAT Test Prep in Denver, SAT Test Prep in San Francisco-Bay Area, GMAT Test Prep in Houston, ISEE Test Prep in Miami, GRE Test Prep in Seattle, SAT Test Prep in Washington DC, ACT Test Prep in Los Angeles, GMAT Test Prep in Phoenix

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

High School Chemistry : Help with Enthalpy

Study concepts, example questions & explanations for High School Chemistry

All High School Chemistry Resources

Example Questions

Example Question #2 : Thermochemistry And Energetics

Example Question #11 : Thermochemistry And Energetics

Example Question #2 : Help With Enthalpy

All High School Chemistry Resources

Report an issue with this question

DMCA Complaint

Contact Information

Address

Complaint Details

Email address:
Your name:
Feedback: