CHEMISTRY Practice Exam #2

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1 CHEMISTRY Practice Exam #2 Section 1 - This section of the exam is multiple choice. Choose the BEST answer from the choices which are given. 1. Which of the following solutions will have the highest concentration of chloride ions? A M NaCl B M MgCl2 C M AlCl3 D M CaCl2 2. How many milliliters of a 9.0 M H2SO4 solution are needed to make 0.35 L of a 3.5 M solution? A ml B ml C. 140 ml D. 900 ml 3. Identify HCl. A) strong electrolyte, weak acid B) weak electrolyte, weak acid C) strong electrolyte, strong acid D) weak electrolyte, strong acid 4. Identify NaCl. A) weak acid B) weak electrolyte C) strong acid D) strong electrolyte 5. Which of the following pairs of aqueous solutions will form a precipitate when mixed? A) NH4NO3 + Li2CO3 B) Hg2(NO3)2 + LiI C) NaCl + Li3PO4 D) AgC2H3O2 + Cu(NO3)2 6. Identify the spectator ions in the following molecular equation. KBr(aq) + AgNO3(aq) AgBr(s) + KNO3(aq) A) Ag+ and Br- B) K+ and NO3 - C) K+ and Br- D) Ag+ and NO3 -

2 7. Give the net ionic equation for the reaction that occurs when aqueous solutions of H2SO4 and KOH are mixed. A) H+(aq) + OH-(aq) H2O(l) B) 2 K+(aq) + SO4 2- (aq) K2SO4(s) C) H+(aq) + OH-(aq) + 2 K+(aq) + SO4 2- (aq) H2O(l) + K2SO4(s) D) H2 2+ (aq) + OH-(aq) H2(OH)2(l) 8. The titration of 25.0 ml of an unknown concentration H2SO4 solution requires 83.6 ml of 0.12 M LiOH solution. What is the concentration of the H2SO4 solution (in M)? A) 0.20 M B) 0.40 M C) 0.10 M D) 0.36 M 9. Which of the following is an acid base reaction? A) C(s) + O2(g) CO2(g) B) 2 HClO4(aq) + Ca(OH)2(aq) 2 H2O(l) + Ca(ClO4)2(aq) C) Fe(s) + 2 AgNO3(aq) 2 Ag(s) + Fe(NO3)2(aq) D) MgSO4(aq) + Ba(NO3)2(aq) Mg(NO3)2(aq) + BaSO4(s) 10. Determine the oxidation state of Sn in Sn(SO4)2. A) +2 B) +4 C) +6 D) What element is undergoing oxidation (if any) in the following reaction? Zn(s) + 2 AgNO3(aq) Zn(NO3)2(aq) + 2 Ag(s) A) Zn B) N C) O D) Ag 12. What is the oxidation number change for the bromine atom in the following unbalanced reduction half reaction: BrO 3 - (aq) + H + (aq) Br - (aq) + I A) -7 B) - 6 C) + 6 D) + 7

3 13. Which of the following signs on q and w represent a system that is doing work on the surroundings, as well as gaining heat from the surroundings? A) q = +, w = - B) q = -, w = + C) q = +, w = + D) q = -, w = Calculate the change internal energy (ΔE) for a system that is giving off 45.0 kj of heat and is performing 855 J of work on the surroundings. A) 44.1 kj B) kj C) kj D) 9.00 x 102 kj 15. A sample of copper absorbs 43.6 kj of heat, resulting in a temperature rise of 75.0 C, determine the mass (in kg) of the copper sample if the specific heat capacity of copper is J/g C. A) 1.51 kg B) 6.62 kg C) 1.26 kg D) 7.94 kg 16. The specific heat capacity of liquid water is 4.18 J/g-K. How many joules of heat are needed to raise the temperature of 5.00 g of water from 25.1 C to 65.3 C? A) 48.1 J B) 840 J C) J D) J 17. Which of the following substances (with specific heat capacity provided) would show the greatest temperature change upon absorbing J of heat? A) 10.0 g Fe, CFe = J/g C B) 10.0 g H2O, CH2O = 4.18 J/g C C) 10.0 g ethanol, Cethanol = 2.42 J/g C D) 10.0 g Au, CAu = J/g C 18. How much energy is evolved during the reaction of 48.7 g of Al, according to the reaction below? Assume that there is excess Fe2O3. Fe2O3(s) + 2 Al(s) Al2O3(s) + 2 Fe(s) ΔH rxn = -852 kj A) 415 kj B) 769 kj C) 241 kj D) 130 kj

4 19. Use the standard reaction enthalpies given below to determine ΔH rxn for the following reaction: 2 NO(g) + O2(g) 2 NO2(g) ΔH rxn =? Given: N2(g) + O2(g) 2 NO(g) ΔH rxn = +183 kj 1/2 N2(g) + O2(g) NO2(g) ΔH rxn = +33 kj A) kj B) -117 kj C) -333 kj D) +115 kj 20. Choose the reaction that illustrates ΔH f for NaHCO3. A) Na(s) + H2(g) + C(s) + O2(g) NaHCO3 (s) B) Na+(aq) + HCO3-1 (aq) NaHCO3 (s) C) Na+(aq) + H2O (l) + CO2 (g) NaHCO3 (s) D) Na(s) + 1/2 H2(g) + C(s) + 3/2 O2(g) NaHCO3 (s) 21. Use the information provided to determine ΔH rxn for the following reaction: ΔH f (kj/mol) CH4(g) + 3 Cl2(g) CHCl3(l) + 3 HCl(g) ΔH rxn =? CH4(g) -75 CHCl3(l) -134 HCl(g) -92 A) -151 kj B) -335 kj C) +662 kj D) +117 kj 22. To what temperature must a balloon, initially at 25 C and 2.00 L, be heated in order to have a volume of 6.00 L? A) 993 K B) 403 K C) 75 K D) 894 K 23. How many moles of CO are contained in a 5.00 L tank at 155 C and 2.80 atm? A) moles B) 1.10 moles C) 2.51 moles D) moles

5 24. What is the volume of 5.60 g of O2 at 7.78 atm and 415K? A) 1.53 L B) 565 L C) 24.5 L D) L 25. Which of the following samples will have the greatest volume at STP? A) 22 g CO B) 22 g He C) 22 g O2 D) 22 g Cl2 26. Place the following gases in order of increasing density at STP. N2 NH3 N2O4 Ar A) N2O4 < Ar < N2 < NH3 B) Ar < N2O4 < N2 < NH3 C) NH3 < Ar < N2 < N2O4 D) NH3 < N2 < Ar < N2O4 27. The density of a gas is 1.43 g/l at STP. What is the gas? A) Cl2 B) S C) O2 D) Ne 28. A g sample of an unknown gas occupies 245 ml at 298 K and 1.22 atm. What is the molar mass of the unknown compound? A) 26.3 g/mol B) 33.9 g/mol C) 12.2 g/mol D) 38.0 g/mol 29. The heat of vaporization of water at 100 C is kj/mol. Calculate the quantity of heat that is absorbed/released when 9.00 g of steam condenses to liquid water at 100 C. A) 20.3 kj of heat are absorbed. B) 20.3 kj of heat are released. C) 81.3 kj of heat are absorbed. D) 81.3 kj of heat are released. 30. Calculate the total quantity of heat required to convert 25.0 g of liquid CCl4(l) from 35.0 C to gaseous CCl4 at 76.8 C (the normal boiling point for CCl4). The specific heat of CCl4(l) is J/(g C), its heat of fusion is 3.27 kj/mol, and its heat of vaporization is kj/mol. A) kj B) 1.43 kj C) 5.74 kj D) 6.28 kj

6 Section 2 - Calculations Involving Chemical Equations Consider the following reaction BaCl 2 (s) + H 2 SO 4 (l) > BaSO 4 (s) + 2 HCl (g) A mixture of 2.65 g of BaCl 2 and 6.78 g of H 2 SO 4 are allowed to react. Molar masses: BaCl 2, H 2 SO 4, BaSO 4, HCl, How many grams of BaSO 4 could theoretically be produced from the 2.65 g of BaCl 2? 2.97 Answer: g 2. How many grams of BaSO 4 could theoretically be produced from 6.78 g of H 2 SO 4? c) Which is the limiting reagent in this reaction? 16.1 Answer: g Answer: d) If 1.25 g of BaSO 4 is actually isolated, what is the percentage yield for the reaction? BaCl2 42.1% Answer:

7 3 - Calculations involving Solutions 1. Calculate the molarity of a solution prepared by dissolving g of LiOH in enough water to give a final volume of 750. ml (Show work.) (1.495 g LiOH) x (1 mol/23.95 g LiOH) = mol LiOH ( mol LiOH)/(0.750 L) = M 2. Describe how you would prepare ml of M NaCl (M = g/mol) from solid NaCl. (.2500 L soln) x (3.000 mol/1.000 L soln) x (58.45 g NaCl/1 mol NaCl) = g NaCl g NaCl is dissolved in enough water to make ml.

8 Section 4 - Follow the directions to solve each problem. 1. An unknown liquid is vaporized in a 273-mL flask by immersion in a water bath at 99 C. The barometric pressure is 753 torr. If the mass of the liquid retained in the flask is g, what is its molar mass? a. Find the number of moles of gas present using the ideal gas law..009 moles b. Using the measured mass of the liquid, find its molar mass. 150 g/mol 2. A small quantity of hydrogen was prepared by the addition of hydrochloric acid to zinc. 195 ml of hydrogen was collected over water at 25 C and 753 torr. from the reaction. (Pwater = 24 torr at 25 C) a. Write the balanced chemical equation for the reaction of zinc metal with hydrochloric acid to yield zinc chloride and hydrogen gas. Zn (s) + 2 HCl (aq)----> ZnCl2 (aq) + H2 (g) b. Correcting for water vapor pressure, what was the pressure of the hydrogen gas collected? 729 torr c. Using the ideal gas equation, calculate the number of moles of hydrogen gas collected? moles d. How many grams of zinc were present in the original reaction?.500 g

CHEMISTRY Practice Exam #2 (KATZ)

CHEMISTRY Practice Exam #2 (KATZ) CHEMISTRY 1710 - Practice Exam #2 (KATZ) Section 1 - This section of the exam is multiple choice. Choose the BEST answer from the choices which are given and write the letter for your choice in the space