Would the change in enthalpy (ΔH) for the dissolution of urea in water be positive or negative?Homemade reactor for water coolingHow do I calculate the enthalpy change when a gas is being used to heat water?Calculating amount of ice required for heat lossHow to calculate the heat of dissolution from a calorimeter experiment?Heat given off from an electrochemical cell compared to mixing reactantsHow to determine whether the enthalpy of solution is positive or negative by calorimetry?Calculating heat of combustion via calorimetryCalculating enthalpy of dissolutionheat of fusion in an equationCalculating the heat of reaction for Mg metal and HCl
Find a stone which is not the lightest one
Mistake in years of experience in resume?
Which big number is bigger?
A Note on N!
Who's the random kid standing in the gathering at the end?
Work requires me to come in early to start computer but wont let me clock in to get paid for it
Why didn't the Space Shuttle bounce back into space as many times as possible so as to lose a lot of kinetic energy up there?
Rudin 2.10 (b) Example
Creating a chemical industry from a medieval tech level without petroleum
Can a barbarian keep raging if she shoves an enemy on her turn?
Where was the County of Thurn und Taxis located?
What is the best way to deal with NPC-NPC combat?
Why is the underscore command _ useful?
How do I deal with a coworker that keeps asking to make small superficial changes to a report, and it is seriously triggering my anxiety?
How long after the last departure shall the airport stay open for an emergency return?
How do I reattach a shelf to the wall when it ripped out of the wall?
Multiple options vs single option UI
Partitioning values in a sequence
Injection into a proper class and choice without regularity
All ASCII characters with a given bit count
Should the Product Owner dictate what info the UI needs to display?
Drawing a german abacus as in the books of Adam Ries
Older movie/show about humans on derelict alien warship which refuels by passing through a star
Can a stored procedure reference the database in which it is stored?
Would the change in enthalpy (ΔH) for the dissolution of urea in water be positive or negative?
Homemade reactor for water coolingHow do I calculate the enthalpy change when a gas is being used to heat water?Calculating amount of ice required for heat lossHow to calculate the heat of dissolution from a calorimeter experiment?Heat given off from an electrochemical cell compared to mixing reactantsHow to determine whether the enthalpy of solution is positive or negative by calorimetry?Calculating heat of combustion via calorimetryCalculating enthalpy of dissolutionheat of fusion in an equationCalculating the heat of reaction for Mg metal and HCl
$begingroup$
To test the properties of a fertilizer, $15.0 mathrm g$ of urea, $ceNH2CONH2(s)$, is dissolved in $150 mathrmmL$ of water in a simple calorimeter. A temperature change from $20.6 mathrm^circ C$ to $17.8 mathrm^circ C$ is measured. Calculate the molar enthalpy of solution for the fertilizer urea
I worked through this question by finding $Q = mcDelta T$, and then dividing $Q$ by the moles of urea present. I can tell the process is endothermic because $Delta T$ is negative, however my answer for $Delta H$ comes out as negative, which would only make sense if this was an exothermic reaction. I'm not sure where I am wrong to be honest.
Here is my work:
$$Delta H = (150 mathrmmL times 1 mathrmg/mL times 4.18 mathrmJ/(g ^circ C) times -2.8 mathrm^circ C) / (15 mathrm g / 60.07 mathrm g) = -7030.59 mathrmJ/mol = -7.03 mathrmkJ/mol$$
TL;DR - question asks for $Delta H$ of an endothermic process, not sure if my answer should be positive or negative
thermodynamics water aqueous-solution enthalpy
edited 1 hour ago
Loong♦
34.4k886181
asked 8 hours ago
ZedEmZedEm
184
New contributor
ZedEm is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
add a comment |
$begingroup$
To test the properties of a fertilizer, $15.0 mathrm g$ of urea, $ceNH2CONH2(s)$, is dissolved in $150 mathrmmL$ of water in a simple calorimeter. A temperature change from $20.6 mathrm^circ C$ to $17.8 mathrm^circ C$ is measured. Calculate the molar enthalpy of solution for the fertilizer urea
I worked through this question by finding $Q = mcDelta T$, and then dividing $Q$ by the moles of urea present. I can tell the process is endothermic because $Delta T$ is negative, however my answer for $Delta H$ comes out as negative, which would only make sense if this was an exothermic reaction. I'm not sure where I am wrong to be honest.
Here is my work:
$$Delta H = (150 mathrmmL times 1 mathrmg/mL times 4.18 mathrmJ/(g ^circ C) times -2.8 mathrm^circ C) / (15 mathrm g / 60.07 mathrm g) = -7030.59 mathrmJ/mol = -7.03 mathrmkJ/mol$$
TL;DR - question asks for $Delta H$ of an endothermic process, not sure if my answer should be positive or negative
thermodynamics water aqueous-solution enthalpy
edited 1 hour ago
Loong♦
34.4k886181
asked 8 hours ago
ZedEmZedEm
184
New contributor
ZedEm is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
add a comment |
$begingroup$
To test the properties of a fertilizer, $15.0 mathrm g$ of urea, $ceNH2CONH2(s)$, is dissolved in $150 mathrmmL$ of water in a simple calorimeter. A temperature change from $20.6 mathrm^circ C$ to $17.8 mathrm^circ C$ is measured. Calculate the molar enthalpy of solution for the fertilizer urea
I worked through this question by finding $Q = mcDelta T$, and then dividing $Q$ by the moles of urea present. I can tell the process is endothermic because $Delta T$ is negative, however my answer for $Delta H$ comes out as negative, which would only make sense if this was an exothermic reaction. I'm not sure where I am wrong to be honest.
Here is my work:
$$Delta H = (150 mathrmmL times 1 mathrmg/mL times 4.18 mathrmJ/(g ^circ C) times -2.8 mathrm^circ C) / (15 mathrm g / 60.07 mathrm g) = -7030.59 mathrmJ/mol = -7.03 mathrmkJ/mol$$
TL;DR - question asks for $Delta H$ of an endothermic process, not sure if my answer should be positive or negative
thermodynamics water aqueous-solution enthalpy
edited 1 hour ago
Loong♦
34.4k886181
asked 8 hours ago
ZedEmZedEm
184
New contributor
ZedEm is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
$endgroup$
To test the properties of a fertilizer, $15.0 mathrm g$ of urea, $ceNH2CONH2(s)$, is dissolved in $150 mathrmmL$ of water in a simple calorimeter. A temperature change from $20.6 mathrm^circ C$ to $17.8 mathrm^circ C$ is measured. Calculate the molar enthalpy of solution for the fertilizer urea
I worked through this question by finding $Q = mcDelta T$, and then dividing $Q$ by the moles of urea present. I can tell the process is endothermic because $Delta T$ is negative, however my answer for $Delta H$ comes out as negative, which would only make sense if this was an exothermic reaction. I'm not sure where I am wrong to be honest.
Here is my work:
$$Delta H = (150 mathrmmL times 1 mathrmg/mL times 4.18 mathrmJ/(g ^circ C) times -2.8 mathrm^circ C) / (15 mathrm g / 60.07 mathrm g) = -7030.59 mathrmJ/mol = -7.03 mathrmkJ/mol$$
TL;DR - question asks for $Delta H$ of an endothermic process, not sure if my answer should be positive or negative
thermodynamics water aqueous-solution enthalpy
thermodynamics water aqueous-solution enthalpy
edited 1 hour ago
Loong♦
34.4k886181
asked 8 hours ago
ZedEmZedEm
184
New contributor
ZedEm is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 1 hour ago
Loong♦
34.4k886181
asked 8 hours ago
ZedEmZedEm
184
New contributor
ZedEm is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 1 hour ago
Loong♦
34.4k886181
edited 1 hour ago
Loong♦
34.4k886181
edited 1 hour ago
Loong♦
34.4k886181
34.4k886181
asked 8 hours ago
ZedEmZedEm
184
New contributor
ZedEm is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 8 hours ago
ZedEmZedEm
184
asked 8 hours ago
ZedEmZedEm
184
184
New contributor
ZedEm is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
ZedEm is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
ZedEm is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
$begingroup$
The sign of Q depends on the perspective. The water temperature decreased because it "lost" heat. The process of dissolving urea required energy, it "gained" energy. If I give you a penny, should that be +1 or -1 penny? Well, it depends who you ask.
In your answer, you are missing a negative sign in $Delta H=−Q$ the way you start out with $Q$ from the perspective of the water.
answered 7 hours ago
Karsten TheisKarsten Theis
5,019643
$endgroup$
add a comment |
Your Answer
StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "431"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);
else
createEditor();
);
function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);
);
ZedEm is a new contributor. Be nice, and check out our Code of Conduct.
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fchemistry.stackexchange.com%2fquestions%2f114339%2fwould-the-change-in-enthalpy-%25ce%2594h-for-the-dissolution-of-urea-in-water-be-positi%23new-answer', 'question_page');
);
Post as a guest
Required, but never shown
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
The sign of Q depends on the perspective. The water temperature decreased because it "lost" heat. The process of dissolving urea required energy, it "gained" energy. If I give you a penny, should that be +1 or -1 penny? Well, it depends who you ask.
In your answer, you are missing a negative sign in $Delta H=−Q$ the way you start out with $Q$ from the perspective of the water.
answered 7 hours ago
Karsten TheisKarsten Theis
5,019643
$endgroup$
add a comment |
$begingroup$
The sign of Q depends on the perspective. The water temperature decreased because it "lost" heat. The process of dissolving urea required energy, it "gained" energy. If I give you a penny, should that be +1 or -1 penny? Well, it depends who you ask.
In your answer, you are missing a negative sign in $Delta H=−Q$ the way you start out with $Q$ from the perspective of the water.
answered 7 hours ago
Karsten TheisKarsten Theis
5,019643
$endgroup$
add a comment |
$begingroup$
The sign of Q depends on the perspective. The water temperature decreased because it "lost" heat. The process of dissolving urea required energy, it "gained" energy. If I give you a penny, should that be +1 or -1 penny? Well, it depends who you ask.
In your answer, you are missing a negative sign in $Delta H=−Q$ the way you start out with $Q$ from the perspective of the water.
answered 7 hours ago
Karsten TheisKarsten Theis
5,019643
$endgroup$
The sign of Q depends on the perspective. The water temperature decreased because it "lost" heat. The process of dissolving urea required energy, it "gained" energy. If I give you a penny, should that be +1 or -1 penny? Well, it depends who you ask.
In your answer, you are missing a negative sign in $Delta H=−Q$ the way you start out with $Q$ from the perspective of the water.
answered 7 hours ago
Karsten TheisKarsten Theis
5,019643
answered 7 hours ago
Karsten TheisKarsten Theis
5,019643
answered 7 hours ago
Karsten TheisKarsten Theis
5,019643
answered 7 hours ago
Karsten TheisKarsten Theis
5,019643
5,019643
add a comment |
add a comment |
ZedEm is a new contributor. Be nice, and check out our Code of Conduct.
ZedEm is a new contributor. Be nice, and check out our Code of Conduct.
ZedEm is a new contributor. Be nice, and check out our Code of Conduct.
ZedEm is a new contributor. Be nice, and check out our Code of Conduct.
Thanks for contributing an answer to Chemistry Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
Use MathJax to format equations. MathJax reference.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fchemistry.stackexchange.com%2fquestions%2f114339%2fwould-the-change-in-enthalpy-%25ce%2594h-for-the-dissolution-of-urea-in-water-be-positi%23new-answer', 'question_page');
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
