# Calorimetry: q NH4NO3 Dissolving + Exothermic/Endothermic?

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In summary, the process involves dissolving 20g of NH4NO3 in 125g of water in a coffee-cup colorimeter, resulting in a temperature decrease from 23.5C to 13.4C. To determine q for the dissolving of the compound, the equation q(calorimeter)=C(calorimeter)*[Delta]T is used. The heat capacity of the solution is not given, so the heat capacity of water is used as an approximation. The final answer is +5.28kJ, indicating an endothermic process. The question did not ask for the molar heat of dissolution, so the number of moles is not taken into account. Overall, the calculation is correct.
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## Homework Statement

20g of NH4NO3 (MM=80.05 g/mol) if dissolved in 125g of water in a coffee-cup colorimeter, the temperature falls from 23.5C to 13.4C. Determine 'q' for the dissolving of the compound. Is the process exothermic or endothermic?

## Homework Equations

q(calorimeter)=C(calorimeter)*[Delta]T

## The Attempt at a Solution

[Delta]T= -10.1
C(calorimeter)=~n(water)*C(water) = 125g H2O/18.016g/mol = 6.9382mol H2O
Ccal=~6.9382mol H2O* 75.291 J/mol C = 522.4 J/C
qcal=52.4J/C*-10.1C= -5.28kJ
q(calorimeter)= -q(chemical) = +5.28kJ

This answer makes sense, however, I don't understand why I am not taking into account the amount of moles NH4NO3. A larger amount of moles would make a larger deviation in T, which would change q.
Why are moles NH4NO3 not taken into account? Also, I'm using the heat capacity (C) of water, not of NH4NO3. The question is asking for 'q' for the dissolving compound. Is this correct?

To be precise you should take into account heat capacity of the solution - not water nor amonium nitrate. It is solution that changes temperature (well - this is more complicated - at first it is pure water that changes temperature, later it is solution, but it doesn't matter at the end). You are not given heat capacity of the solution, so you used heat capacity of water, which is the best approximation available to you.

You were asked to determine amount of heat needed for dissolving the compound - and looks like you did OK.

Number of moles will be required if the question asked for molar heat of dissolution - but it didn't.

--

I would like to clarify a few things. Firstly, the formula used for calorimetry is q = mCΔT, where q is the heat transferred, m is the mass of the substance, C is the specific heat capacity, and ΔT is the change in temperature. In this case, we are dealing with a coffee-cup calorimeter, so the heat transferred is equal to the heat absorbed by the water and the calorimeter.

In this experiment, we are dissolving 20g of NH4NO3 in 125g of water. The change in temperature is from 23.5C to 13.4C, which means that the water has lost heat to the surroundings. This indicates that the process is exothermic, as the heat is being released from the system.

To determine the heat transferred, we need to take into account the specific heat capacity of both NH4NO3 and water. The formula for this would be q = mNH4NO3*C(NH4NO3)*ΔT + mH2O*C(H2O)*ΔT. We can assume that the specific heat capacity of NH4NO3 is similar to that of water, so we can simplify the equation to q = (mNH4NO3 + mH2O)*C(H2O)*ΔT.

In this case, the mass of NH4NO3 is 20g and the mass of water is 125g, so the total mass is 145g. Plugging this into the equation, we get q = (20g + 125g)*4.18 J/gK*(-10.1C) = -5.24 kJ.

Therefore, the heat transferred for this process is -5.24 kJ, which means that the dissolving of NH4NO3 is an exothermic process. It is important to take into account the specific heat capacities of all substances involved in the reaction to get an accurate value for the heat transferred.

## 1. What is calorimetry?

Calorimetry is the scientific measurement of heat transfer in a chemical reaction or physical process. It involves using a calorimeter, which is a device that measures the change in temperature of a substance, to determine the amount of heat released or absorbed.

## 2. What is q NH4NO3 Dissolving?

q NH4NO3 Dissolving refers to the amount of heat released or absorbed when ammonium nitrate (NH4NO3) is dissolved in water. This is typically measured using a calorimeter, and the value can indicate whether the dissolution process is exothermic or endothermic.

## 3. Is the dissolution of NH4NO3 exothermic or endothermic?

The dissolution of NH4NO3 can be both exothermic or endothermic, depending on the specific conditions. In general, dissolving salts such as NH4NO3 in water tends to be an exothermic process, meaning that heat is released. However, if the surrounding temperature is lower than the initial temperature of the reactants, the process can be endothermic.

## 4. What factors can affect the q NH4NO3 Dissolving value?

Several factors can influence the q NH4NO3 Dissolving value, including the initial temperature of the reactants, the concentration of the solution, and the amount of NH4NO3 being dissolved. Other factors such as the presence of impurities or the use of a different solvent can also impact the value.

## 5. Why is it important to measure q NH4NO3 Dissolving in a chemical reaction?

Measuring q NH4NO3 Dissolving can provide valuable information about the energy changes that occur during a chemical reaction. It can help determine the direction of the reaction (exothermic or endothermic), as well as the amount of heat released or absorbed. This information is crucial for understanding the thermodynamics of a reaction and can also be used to calculate other important parameters, such as enthalpy and entropy.

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