Chemistry 1A Fall 2009 Midterm Exam 2 October 13 2009 90 min closed book Name KEY SID GSI Name The test consists of 6 short answer questions and 20 multiple choice questions Put your written answers in the boxes provided Answers outside the boxes may not be considered in grading Useful Equations and Constants Write your name on every page of the exam pH log H3O pX log X Question Page Points Score X 10 pX Kw 1 10 14 Multiple Choice 1 20 2 5 78 Strong acids and bases Question 21 6 8 HCl LiOH HNO3 NaOH Question 22 23 7 9 KOH H2SO4 HClO4 Question 24 8 10 HBr HI Question 25 9 5 Acid dissociation constants Ka CH3COOH 1 75 10 5 Question 26 10 10 NH4 5 70 10 10 HCN 6 2 10 10 Total 120 CH3NH3 2 3 10 11 H2CO3 4 45 10 7 CH3 3NH 1 58 10 10 Name GSI Multiple choice Circle the BEST answer and bubble the choice on your scantron form How many moles of HCl must be added to 1 liter of water to make OH 10 9 M A 10 9 moles B 10 5 moles C 10 2 moles D there is no OH in HCl aq B 3 points 1 2 What is the pH of a 0 020M HCl solution A 1 0 B 0 020 C 2 0 D 3 points C 2 point 3 D 1 7 What is the pH of a 1 00M formic acid HCOOH solution Ka 1 80 10 4 A 0 013 B 0 00 C 1 9 D 3 7 C 3 points A 2 point What is the solubility of the salt lead chloride PbCl2 Ksp 1 7 10 5 A 4 1 10 3M B 4 3 10 6 M C 1 7 10 5M D 1 6 10 2 M D 3 points A 2 point 4 5 Which solution requires the largest volume of 0 10 M HCl to reach the equivalence point A 50 mL 1 0 M NH3 B 200 mL 2 0 M NaCl C 100 mL 0 25 M NaOH D 100 mL 0 40 M NaOH A 3 points D 2 point 6 Which reaction is an oxidation reduction reaction A 6FeCl2 aq K2Cr2O7 aq 14HCl 6FeCl3 aq 2CrCl3 aq 2KCl aq 7H2O l B AgNO3 aq NaCl aq AgCl s NaNO3 aq C CaCO3 s CaO s CO2 g D SO3 g H2O l H2SO4 aq A 3 points Note There is a small error in B The A is missing for AgCl 7 The solid CaSO4 is dissolved in 1 0 L of water The solution formed establishes an equilibrium with a large amount of solid CaSO4 If you add 10 mL water and examine the solution after 10 minutes A the concentration decreases B the equilibrium constant increases C the solubility remains the same D the solubility decreases C 3 points A 2 point Page 2 of 10 Name GSI The diagrams shown below represent the concentration of reactants and products over time Which of the graphs represent systems that have reached equilibrium Why Represents reactants 0 0 9 0 time A B C D C 3 points 0 C concentration B concentration concentration A Represents products 0 time 0 time D concentration 8 0 0 time Graph A because the concentrations are equal Graph B because the concentrations are constant Graph C because the concentrations are constant Graph D because the concentrations are constant B 2 point What conclusion can you draw from the data in the table Ksp Mg OH 2 pH of saturated solution 13 2 0 x 10 10 4 Ba OH 2 2 6 x 10 13 x A Mg OH 2 is not an electrolyte B Mg OH 2 is more soluble than Ba OH 2 C Both Mg OH 2 and Ba OH 2 are completely dissociated into ions in solution D Molecules of Mg OH 2 in solution are only partially dissociated E Mg OH 2 is a weak base C 4 points E 3 points D 3 points 10 Equal moles of nitric acid HNO3 and sodium hydroxide NaOH are mixed HNO3 aq NaOH aq NaNO3 aq H2O l What happens to the equilibrium concentrations if you add solid sodium nitrate NaNO3 s to the solution A The reaction proceeds to form more products B The pH increases above 7 C The pH remains at 7 D There is less water in the solution E The density of the solution increases C 4 points E 3 points D 3 points 11 Which compound will form a solution with the lowest pH Data is on page 1 B Na2CO3 C N CH3 3 D NaBr E CH3COONa A NH4Cl A 4 points D 2 point Page 3 of 10 Name GSI 12 Which of the substances listed below is the strongest acid A B C D E E 4 points D 3 points C 2 points 13 An aqueous solution of 1 mole of NaOH sodium hydroxide was added to an aqueous solution of 1 mole of CH3COOH acetic acid Which of the following statements is true about the solution A It contains more H3O ions that OH ions B It contains fewer H3O ions than OH ions C It contains as many H3O ions as OH ions D It contains neither H3O ions nor OH ions E It contains as many CH3COO ions as Na ions B 4 points E 3 points C 3 points 14 A 0 10 M solution of congo red indicator changes color from the blue violet HIn molecule to the red In ion at a pH of 4 What is the equilibrium constant for the dissociation of congo red A 0 10 B 0 00010 C 10000 D 4 E 3 16 10 3 B 4 points E 3 points An equilibrium mixture of gases consists of CO 2 5 10 3 M O2 1 6 10 3 M and CO2 3 2 10 2 M Determine the equilibrium constant for the formation of CO2 B 1 0 105 C 1 3 10 7 D 1 3 10 4 E 1 0 x 10 5 A 8 0 103 B 5 points A 4 points 15 16 Equal moles of HCl CH3COOH and NH3 are mixed in water What are the three species in solution present in the highest concentrations A HCl CH3COOH and NH3 B H CH3COO and NH4 C H NH3 and CH3COOH D H Cl and NH4 E Cl NH4 and CH3COOH E 5 points B 4 points Page 4 of 10 Name GSI 17 The illustration shows an equilibrium mixture for the reaction of A2 and B2 A2 g B2 g 2AB g How can you produce this equilibrium mixture A Mix 4 molecules of A2 and 4 molecules of B2 and allow them to react B Mix 6 molecules of A2 and 6 molecules of B2 and allow them to react C Begin with 6 molecules of AB and allow some to decompose D Begin with 8 molecules of AB and allow some …