Calculating ΔE for a Reaction The reaction of nitrogen with hydrogen to make ammonia has ΔH° = -92.2 kJ. What is the value of ΔE in kilojoules if the reaction is carried out at a constant pressure of 40.0 atm and the volume change is -1.12 L? N2(g) + 3 H2(g) → 2 NH3(g) ΔH° = -92.2 kJ

Question

Calculating ΔE for a Reaction

The reaction of nitrogen with hydrogen to make ammonia has ΔH° = -92.2 kJ. What is the value of ΔE in kilojoules if the reaction is carried out at a constant pressure of 40.0 atm and the volume change is -1.12 L?

[latex]N_2[/latex](g) + 3 [latex]H_2[/latex](g) → 2 [latex]NH_3[/latex](g) ΔH° = -92.2 kJ

STRATEGY

We are given an enthalpy change ΔH, a volume change ΔV, and a pressure P and asked to find an energy change ΔE. Rearrange the equation ΔH = ΔE + PΔV to the form ΔE = ΔH - PΔV, and substitute the appropriate values for ΔH, P, and ΔV:

Accepted Answer

[latex]\begin{aligned}& \Delta E=\Delta H-P \Delta V \quad ext { where } \Delta H=-92.2 \mathrm{~kJ} \& \begin{aligned}& P \Delta V=(40.0 \mathrm{~atm})(-1.12 \mathrm{~L})=-44.8 \mathrm{~L} \cdot ext { atm } \&=(-44.8 \mathrm{~L} \cdot ext { atm })\left(101 \frac{\mathrm{J}}{\mathrm{L} \cdot \mathrm{atm}} ight)=-4520 \mathrm{~J}=-4.52 \mathrm{~kJ} \& \Delta E=(-92.2 \mathrm{~kJ})-(-4.52 \mathrm{~kJ})=-87.7 \mathrm{~kJ}\end{aligned}\end{aligned}[/latex]

Note that ΔE is smaller (less negative) than ΔH for this reaction because the volume change is negative. The products have less volume than the reactants, so a contraction occurs and a small amount of PV work is gained by the system.

Question 8.4: Calculating ΔE for a Reaction The reaction of nitrogen with ......

Related Answered Questions

Verified Answer:

Verified Answer:

Predicting the Signs of ΔH, ΔS, and ΔG for a Reaction What are the signs of ΔH, ΔS, and ΔG for the following nonspontaneous transformation? ...

Verified Answer:

Using the Free-Energy Equation to Calculate Equilibrium Temperature Lime (CaO) is produced by heating limestone (CaCO3) to drive off CO2 gas, a reaction used to make Portland cement. Is the reaction spontaneous under standard conditions at 25 °C? Calculate the temperature at which the reaction ...

Verified Answer:

Predicting the Sign of ΔS for a Reaction Predict whether ΔS° is likely to be positive or negative for each of the following reactions: (a) H2C=CH2(g) + Br2(g) → BrCH2CH2Br(l) (b) 2 C2H6(g) + 7 O2(g) → 4 CO2(g) + 6 H2O(g) ...

Verified Answer:

Using Standard Heats of Formation to Calculate ΔH° Oxyacetylene welding torches burn acetylene gas, C2H2(g). Use the information in Table 8.2 to calculate ΔH°in kilojoules for the combustion reaction of acetylene to yield CO2(g) and H2O(g). STRATEGY Write the balanced equation, look up the ...

Verified Answer:

Verified Answer:

Verified Answer:

Calculating the Amount of Heat Released in a Reaction How much heat in kilojoules is evolved when 5.00 g of aluminum reacts with a stoichiometric amount of Fe2O3? 2 Al(s) + Fe2O3(s) → 2 Fe(s) + Al2O3(s) ΔH° = -852 kJ ...

Verified Answer:

Verified Answer: