Question

Practice Questions Exam 2 Fall 2019 9. The reaction profile represents the following chemical equation: AB-CD Calculate the activation energy (Ea) and AH of the reaction at 200 K Page 2 of 5 14. Consider the following reaction at 1700*C. 2CH ) CH.(g) + 3H2(g) Initially, the reaction mixture contains only [CH] -0.320 M. At equilibrium, the mixture contains [C,H,1 -0.070 M. What is the equilibrium constant for this reaction at 1700 °C? 1200 kJ 500 kJ 200 kJ Ea A. 700 kJ B. 700 kJ C. 1200 kJ D 1200 kJ E 300 kJ F. 300 kJ ΔΗ -300 kJ +300 kJ -300 kJ +300 kJ -700 kJ +700 kJ 15. If Ke - 1.70 x 10 for the reaction, N2(g) + O2(g) 2 NO(g) and the initial concentrations are [N2] -0.515 M. [02] -0.175 M, and [NO] -0.135 M, what is required for the reaction to reach equilibrium? A. Nothing, because the reaction is already at equilibrium B. More NO must form. C More 02 must form D. A catalyst must be added. 10. For the hypothetical reaction, 2A(s)+B(g) 3C(8) write the equilibrium constant expression. 16. Consider the following reactionat 100°C. N2048) 2NO2(g) Ke -0.36 A reaction mixture at 100 °C initially contains (NO2) -0.100 M. What is the equilibrium concentration of NO2? 11. If Ke-46.9 at 700 K for the reaction, PCI(g) PC13(g) + Cl (g) what is Kc for the reverse reaction? 12. What is the value of Kp for the reaction shown in Question 12? 17. A decrease in volume will have what effect on the reaction below? C(s) + H2O(g) + CO(g) + H2(g) a. K decreases b. more CO(g) and H2(g) are produced c. no effect d. more H2O(g) produced e. K increases 13. In which of the following situations will Keq change? A when reactant concentrations change B. when temperature is changed c. when product concentrations change D. when a catalyst is added

Answer 1

9)
According to collision theory i Reaclants assumed to be hard spheres and these molecules are in state of random motion " Reaction will take place due to collision of reaclant but all collision are not effective to bring about the reaction Effective collision are those which the Colliding molecule possess minimum energy known as the threshold energy and are properly oriented : rate con levit - ZAR - Ea/RT. E is the minimum a relative kinetic energy the reactant must possess for the Conversion into product Let Initial Energy of Reaclant = Er Thereshold Energy & Eth. of Ex L Eth, some extra energy has to supplied to raise the level of threshold energy of the reaclant that is known as Activation Energy (Ea) cs Scanned with Ea = Eth-Ey:

Eru) . | AB for conversion of A B , readlant have tcross a energy barries °C= Etus. = ATS Hea Reaclánt.directly do not | React Prod. me change into product. some energy is aboarbed Reaction Progress Reaction Progress equal to activation energy which leads to loo- -sening of old bond and formation of new. bonds between them. This state is called bransition Säle (75) All Energy of Reachon = Eproduct. - Ereactant Alt Energy of reaca = Ep - Er З» ки ача алар 1200 Energy VTS_ Eth = 1200 kJ, Ey = gook ] _Ep = 200 kJ sco + AB 200+ Reaction = 700 k a mar man . & Eq = Eth - Er = (1200 – 500) kJ progress AH = Ep -Ex = (200 -500) KJ Scanned with GamScanner = - 300 kJ (exothermie as energy is released).

activation energy E_a is +700 kJ

AH = -300kJ