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Instant cold packs used to ice athletic injuries on the field contain ammonium nitrate and water separated by a thin plastic divider. When the divider is broken, the ammonium nitrate dissolves according to the endothermic reaction:

In order to measure the enthalpy change for this reaction, 1.25 g of NH4NO3 is dissolved in enough water to make 25.0 mL of solution. The initial temperature is 25.8 C, and the final temperature (after the solid dissolves) is 21.9 C. Calculate the change in enthalpy for the reaction in kJ. (Use 1.0 g/mL as the density of the solution and 4.18 J/g # C as the specific heat capacity.)

$+26.1 \mathrm{~kJ} / \mathrm{m})$

Chemistry 102

Chemistry 101

Chapter 9

Thermochemistry

Thermodynamics

Chemical reactions and Stoichiometry

University of Central Florida

Drexel University

University of Kentucky

University of Toronto

Lectures

00:42

In thermodynamics, the zer…

01:47

A spontaneous process is o…

09:29

Instant cold packs used to…

01:11

03:04

01:31

Adding $5.44 \mathrm{g}$ o…

03:16

A $3.53$ - $\mathrm{g}$ sa…

0:00

(a) When a 4.25 -g sample …

01:14

Ammonium nitrate decompose…

05:44

An ice cube tray contains …

07:00

04:10

An ice cube with a mass of…

05:49

$6.01 \mathrm{kJ} / \mathr…

01:41

A 0.250 -g chunk of sodium…

03:35

A $0.250-g$ chunk of sodiu…

06:32

The molar heat capacity of…

04:38

03:46

The value of $\Delta U$ fo…

03:25

In a coffee-cup calorimete…

A 20.0 -g sample of ice at…

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A $20.0-\mathrm{g}$ sample…

So in this problem, we're given the reaction and h for and all three solid forms an H for plus Aquarius plus an or three minus Aquarius. And we want to find the Delta h of this reaction. And so to do this, we want to take specific heat times mass of water in this case times delta T the change in temperature divided by and the number of moles of the substance, which in this case is an H for in all three. And then multiply that by a thousand in order to convert from Jules per mole into Killa Jules per mall. And so are we have all these values we know that sea is the specific heat of water is four point one grams over Jules degrees Celsius. The mass of water were given that we have twenty five point zero Miller leaders as well as a density of one gram per mil leader. So we have twenty five point zero grams. Our delta T is our final temperature twenty five point eight degrees Celcius minus our initial temperature, twenty one point nine degrees Celsius or a change in temperature is three point nine degrees Celsius and Then we confined our number of moles by taking our mass of N H for N O three and dividing it by its Mueller Mass. Eighty point zero five to grams per mole. And so that gives us zero point zero one five six Smalls. And so now that we have all of this, we can plug it into our delta h of reaction equation. And so we get that Delta H of reaction is equal to the specific heat. Four point one eight grams per jewel degrees Celsius times the mass. Twenty five point zero grams The mass of water that is times the delta T three point nine degrees Celsius, divided by zero point zero one five six moles times a thousand in order to convert to kill a Jules promote from Jules Permal. And that gives us that we have positive twenty six point one killer Jules Permal And we know that our answer is positive since the reaction is Ando thermic and so that is our final answer

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