Chemical Equilibrium Pre and P
Chemical Equilibrium Pre and Post Lab Questions 1. Which is truefor the following reaction? N2 (g) + 3H2 (g) —–> 2NH3 (g) +heat a. For the reverse reaction, ΔH is negative. b. For thereverse reaction, ΔH is negative. c. All of the above. d. None ofthe above. Consider the following equilibrium when answeringquestions 2 to 6. N2O4 (g) ——> 2 NO2 (g) ΔH = 56.9 kJ 2 .Which of the following is true about reaction when an amount of NO2(g) is added to the equilibrium reaction? a. Equilibrium will shiftto consume N2O4 (g). b. Equilibrium will shift to produce more NO2(g). c. Equilibrium will shift to consume the NO2 (g). d. No effecton the equilibrium. 3. Which of the following is true aboutreaction when the pressure is lowered by increasing the volume ofthe reaction container. a. Equilibrium will produce more N2O4 (g)to offset the pressure drop. b. Equilibrium will shift to the rightto produce more NO2 (g). c . Equilibrium will shift to consume moreNO2 (g). d. No effect on the equilibrium. 4. Which of the followingis true about reaction when the temperature is raised? a.Equilibrium will shift to the left. b. Equilibrium will shift tothe right. c. Equilibrium will shift to produce more heat. d. Noeffect on the equilibrium. 5. Which of the following is true aboutreaction when a catalyst is added to the system? a. Equilibriumwill shift to the left. b. Equilibrium will shift to the right. c.Equilibrium will shift to lower the heat. d. No effect on theequilibrium. 6. Which of the following will increase the Keq of theequilibrium in reaction ? a. Add NO2 (g). b. Heat the reactioncontainer. c. Put the reaction container in ice. d. Add a catalyst.Consider the following equilibrium when answering questions 7 and8. CO (g) + 3 H2 (g) ———> CH4 (g) + H2O (g) 7. Which ofthe following is true about reaction when the concentration of COis increased? a. Equilibrium will shift to the left. b. Equilibriumwill shift to the right. c. No effect on the equilibrium. DEquilibrium constant will increase. 8. Which of the following istrue about reaction when the concentration of CH4 (g) is increased?a. Equilibrium will shift to the left. b. Equilibrium will shift tothe right. c. No effect on the equilibrium. d. Equilibrium constantwill decrease. Consider the following equilibrium when answeringquestions 9 and 11. 2C2H2 (g) + 5 O2 (g) ———> 4 CO2 (g) +2 H2O (g) + heat 9. Which of the following is true about reactionwhen the concentration of O2 (g) is decreased? a. Equilibrium willshift to the left. b. Equilibrium will shift to the right. c. Noeffect on the equilibrium. d. Equilibrium constant will decrease.10. Which of the following is true about reaction when thetemperature is increased? a. Equilibrium will shift to the left. b.Equilibrium will shift to the right. c. No effect on theequilibrium. d. No effect on the equilibrium constant. 11. Which ofthe following is true about reaction when the pressure is increasedby decreasing the volume of the reaction container? a. Equilibriumwill shift to the left. b. Equilibrium will shift to the right. c.No effect on the equilibrium. d. No effect on the heat produced.Consider the following equilibrium when answering questions 12 and17. 2 H2O (g) + 2 Cl2 (g) + heat ———-> 4 HCl (g) + O2 (g)12. Which of the following is true about reaction when the reactionmixture is heated. a. Equilibrium will shift to the left. b.Equilibrium will shift to the right. c. No effect on theequilibrium. d. No effect on the equilibrium constant. 13. Which ofthe following is true about reaction when O2 (g) is added to themixture. a. Equilibrium will shift to the left. b. Equilibrium willshift to the right. c. No effect on the equilibrium. d. Equilibriumconstant will decrease. 14. Which of the following is true aboutreaction when the pressure is increased by the addition of an inertgas? a. Equilibrium will shift to the left. b. Equilibrium willshift to the right. c. No effect on the equilibrium. d. Equilibriumconstant will decrease. 15. Which of the following is true aboutreaction when the size of the reaction container is increased? a.Equilibrium will shift to the left. b. Equilibrium will shift tothe right. c. No effect on the equilibrium. d. Equilibrium constantwill increase. 16. Consider the reaction N2 (g) + O2 (g)———> 2 NO (g) + heat The product is favored a. When thereaction temperature is increased. b. When the volume of thereaction container is reduced. c. When He (g) is added to thereaction. d. When the reaction temperature is lowered. 17. When thetemperature of an equilibrium system for the following reaction isincreased, CO (g) + H2O (g) ——–> CO2 (g) + H2 (g) thereaction shifts to the left. Which of the following is true? a.Equilibrium is exothermic. b. Equilibrium is endothermic. c. Noneof the above. d. All of the above
Answer:
1) The given reaction is
N2 + 3 H2 ——-> 2 NH3 +heat
Heat is a product of the reaction, i.e, the reaction releasesheat into the surroundings. Hence, ΔH for the forward reaction(formation of NH3 from N2 and H2)has negative value and consequently, the reverse reaction(decomposition of NH3 to form N2 andH2) has positive ΔH (ans).
I explained the answer; however choices (a) and (b) are bothsame. Kindly check the question and choose the correct option.
2) The equilibrium reaction is
N2O4<======> 2 NO2 ; ΔH =56.9 kJ
The equilibrium constant is
K =[NO2]2/[N2O4]
K remains constant at a particular temperature.
When excess NO2 is added, [NO2] increasesand hence [N2O4] must increase to keep Kconstant. This is possible only when the equilibrium shifts in thereverse direction, producing more N2O4.
Therefore, (c) is the correct statement.
3) Assume ideal behavior of the gases. The pressure of an idealgas is inversely proportional to the volume. Again, as per the gaslaw, the volume of an ideal gas is directly proportional to thenumber of moles of the gas. Therefore, the higher the number ofmoles of gases, the higher is the volume and consequently, thelower is the pressure.
When the pressure is lowered, the equilibrium will shift in thedirection where the number of moles of gases is more. Since theforward reaction proceeds with an increase in the number of molesof gaseous products, hence the equilibrium shifts to the right.Therefore, statement (b) is correct.
4) The enthalpy change for the reaction is positive. Hence thereaction is endothermic. Endothermic reactions are favored by hightemperatures, hence the equilibrium shifts to the right, producingmore NO2. Thus, statement (b) is correct.
5) A catalyst alters the rate of both the forward and thereverse reactions, but keeps the position of the equilibriumunchanged. Hence, a reaction at equilibrium is unaffected by theaddition of a catalyst. Statement (d) captures the correctessence.
6) The equilibrium constant, Keq depends only on thetemperature of the system. Any effect that aims to change thetemperature of the system will alter the value of Keq.Since statements (b) and (c) both describe a change in temperature(b increases the temperature while c reduces the temperature).Hence, both the processes will change the value of Keq.Therefore, both (b) and (c) are correct.
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