In a coffee-cup calorimeter, 1.60 g NH4 NO3 is mixed with 75.0 g water at an initial temperatu

In a coffee-cup calorimeter, 1.60 g NH4 NO3 is mixed with...

In a coffee-cup calorimeter, $1.60 \mathrm{~g} \mathrm{NH}_{4} \mathrm{NO}_{3}$ is mixed with $75.0 \mathrm{~g}$ water at an initial temperature of $25.00^{\circ} \mathrm{C}$. After dissolution of the salt, the final temperature of the calorimeter contents is $23.34^{\circ} \mathrm{C}$. Assuming the solution has a heat capacity of $4.18 \mathrm{~J} /{ }^{\circ} \mathrm{C} \cdot \mathrm{g}$ and assuming no heat loss to the calorimeter, calculate the enthalpy change for the dissolution of $\mathrm{NH}_{4} \mathrm{NO}_{3}$ in units of $\mathrm{kJ} / \mathrm{mol}$.

Key Concepts

Molar Conversion

Molar conversion involves translating the total energy change observed in an experiment to a per-mole basis by using the molecular weight of the substance. This conversion is important for standardizing the enthalpy change so that it can be compared across different reactions and conditions.

Enthalpy Change

Enthalpy change (?H) represents the heat absorbed or released by a system under constant pressure. In calorimetric experiments, the measured energy change is assumed to be equal to the reaction enthalpy, thereby linking the observed temperature change to the overall energy change per mole of reactant involved in the process.

Specific Heat Capacity

Specific heat capacity is a property that describes the amount of heat required to raise the temperature of a unit mass of a substance by one degree Celsius. It is crucial in calorimetric calculations since it relates the measured temperature change to the energy change absorbed or released by the system.

Heat Transfer Calculation

The heat transfer calculation, typically expressed as q = m * c * ?T, involves the mass of the solution, its specific heat capacity, and the observed change in temperature. This equation allows one to quantify the energy involved in the process, which is essential for determining the reaction’s thermal nature (endothermic or exothermic).

Calorimetry

Calorimetry is the experimental measurement of heat exchanged during physical changes or chemical reactions. In this context, a coffee-cup calorimeter, which operates at constant atmospheric pressure, is used to measure the heat change associated with the dissolution process by monitoring temperature variations. This concept is central to studies involving energy changes during reactions.

Transcript

0:00 This problem.

00:01 We're going to determine the changing in therapy and killed jules prum old.

00:06 Now we're given that we are going to dissolve a given amount of ammonium nitrate, and that's the image for a no.

00:14 Three aqua solution.

00:16 Were given an amount of 1.60 grams.

00:19 That's our souls that were dissolving in the coffee cup calorie meter were also given initial temperature and final temperature.

00:28 Now notice that we're starting at a higher temperature and going down to a lower temperature.

00:34 So that tells us this particular reaction or dissolution off the salt is going to be endo thermic.

00:41 It's taking heat from the calorie meter.

00:44 Two, uh, performed the dissolution or basically dissolve ah, their respective ions into the water, the ions being the ammonium ion in the night.

00:55 Right, ayan? so, uh, we have all the information we need.

01:00 Um, we do have the massive water as well.

01:03 It's 75 grams, and then we can use thes specific heat of water.

01:07 And that's going to be the 4.18 grams.

01:11 Per i'm sorry, jules.

01:12 Program degree celsius.

01:15 So i'm gonna go and start a second screen, and i do have some information as far as what we're gonna do for calculations now.

01:23 Ah, the cc is the copy cup calorie meter.

01:26 We know that the water and the calumet er is going to lose heat.

01:32 So i have negative cubes.

01:35 That's heat being emitted from the water.

01:38 And the reaction is going to take that heat and actually performed the reaction.