EXAM PRACTICE QUESTIONS Chapter 17 1 Write the equilibrium constant expression for the following reaction 4 NH3 g 5 O2 g 4 NO g 6 H2O g Answer K c NO 4 H2O 6 NH3 4 O2 5 Some nitrogen and hydrogen gases are pumped into an empty 5 00 L vessel at 500 cid 113 C When equilibrium was established 3 00 moles of N2 2 10 moles of H2 and 0 298 moles of NH3 were present Evaluate Kc at 500 cid 113 C 3 H2 g N2 g 2 NH3 g Answer Kc 0 080 3 The equilibrium constant Kc for the following reaction is 0 0154 at a high temperature A mixture in a container at this temperature has the concentrations H2 1 11 M I2 1 30 M and HI 0 181 M Will more product or more reactant be formed or is the reaction at equilibrium H2 g I2 g 2 HI g Answer Q 0 227 Kc shifts left reactants are produced 4 Kc 0 040 for the system below at 450 cid 113 C If a reaction is initiated with 0 20 mole of Cl2 and 0 20 mole of PCl3 in a 1 0 L container what concentration of PCl5 will be present at equilibrium PCl5 g PCl3 g Cl2 g Answer 0 13 M 2 5 Consider the equilibrium system below 2 Cl2 g 2 H2O g heat 4 HCl g O 2 g B lower the temperature C decreasing volume at constant temperature A adding Cl2 Predict the affect on the equilibrium due to the application of each of the following stresses Answer right left left right 6 A system at equilibrium in a 1 0 L container was found to contain 0 20 mol of A 0 20 mol B 0 40 mol C and 0 40 mol of D If 0 15 mol of A and 0 15 mold of B are added to this system what will be the new equilibrium concentration of A D decreasing O2 A g B g C g D g Answer 0 25 M 7 Consider the equilibrium system below PCl5 g PCl3 g Cl2 g At 250 cid 113 C a sample of PCl5 was placed in a 24 L evacuated reaction vessel and allowed to come to equilibrium Analysis showed that at equilibrium 0 42 mole of PCl5 0 64 mole of PCl3 and 0 64 mole of Cl2 were present in the vessel Calculate Kp for the reaction at 250 cid 113 C Answer 1 8 8 A sample of only solid ammonium chloride was heated in a 1 00 L container at 500 cid 113 C NH4Cl g NH3 g HCl g At equilibrium the pressure of NH3 g was found to be 1 75 atm What is the equilibrium constant Kc for the decomposition at this temperature Answer 7 62 cid 117 10 4 9 Consider the following reaction at 25 cid 113 C for which cid 39 H cid 113 is 26 9 kJ and cid 39 S cid 113 is 11 4 J K Evaluate the equilibrium constant Kp for the reaction at 25 cid 113 C R 8 314 J mol cid 152 K Answer 2 05 cid 117 105 Cl2 g I2 g 2 ICl g 10 The following picture represents a mixture that contains A atoms B atoms and AB and B2 molecules for the hypothetical reaction given below Calculate the equilibrium constant Kc for the reaction Answer 1