Question

Could someone please tell me the answer and providing reasoning as to why?

You perform three different reactions at constant pressure and note the heat associated with the three reactions are equal. Reaction 1 produces gas, reaction 2 consumes it and reaction 3 has no gaseous substances as reactants or products. Which statement below is true? Note: Greatest refers to the value, not the magnitude, so -2 is greater than -5 and 1 is greater than both Select one: a. The internal energy change is greatest for the reaction producing gas and smallest for the reaction consuming gas. b. The internal energy change is greater for the reactions producing and consuming gas than the reaction which does not involve gas. XWould you expect the same result for reactions producing and consuming gas. c. The internal energy change is greatest for the reaction consuming gas and smallest for the reaction producing gas. d. The internal energy change of the three reactions are equal. e. The internal energy change for a reaction is a complicated function and cannot be compared using the information available in this question

Answer 1

For Reaction 1:

Given that this reaction produces gases.

Therefore, change in no.of moles of gaseous reactants and products will be positive.

ie; Ang = +ve

Also, we have,

ΔΗ = ΔU + ΔηφRT

Where, $\Delta U$ is change in internal energy, is universal gas constant and is temperature.

Hence, For the reaction 1:

Η >

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For Reaction 2:

Given that this reaction consume gases.

Therefore, change in no.of moles of gaseous reactants and products will be negative.

ie; Ang = -ve

Also, we have,

ΔΗ = ΔU + ΔηφRT

Hence, For the reaction 2:

RIܨܠ - 18 - Hܠ

AHS AV

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For Reaction 3:

Given that this reaction doesn't involve gases.

Therefore, change in no.of moles of gaseous reactants and products will be zero.

le; Ang = 0

Also, we have,

ΔΗ = ΔU + ΔηφRT

Hence, For the reaction 3:

ΔΗ = ΔU +0

AH = AV

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We know that, At constant pressure heat energy associated with a reaction is known as change in enthalpy.

ΔΗ = gp

Given that the heat associated with all reactions are equal.

That is $\Delta H$ is equal for all three reactions.

Therefore comparing the equations (1), (2) and (3) we get that, Reaction 2 (consuming gas) has the greatest change in internal energy and the smallest for Reaction 1 (producing gas).

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Therefore correct option is option (c) The internal energy change is greatest for the reaction consuming and smallest for the reaction producing gas.

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