Chemistry Exam #2 Version A

Exam #2 version A Name___________________________________ MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) In which species does sulfur have the highest oxidation number? A) S8 (elemental form of sulfur) 1) B) K 2 SO4 C) H2S D) H2SO3 E) SO2 2) The molarity of a solution prepared by diluting 43.72 mL of 5.005 M aqueous K 2 Cr2O7 to 500 mL is __________. A) 0.0879 B) 0.0044 C) 57.2 D) 0.870 2) E) 0.438 3) What is the maximum amount of SO3 in moles that can be produced by the reaction of 1.0 mol of S 3) with 1.0 mol of O2 via the equation below? S (s) + O2 (g) → SO3 (g) (not balanced) A) 1 B) 0.66 C) 2 D) 1.5 E) 3 4) The value of ΔH° for the reaction below is -126 kJ. _________kJ are released when 2.00 mol of NaOH is formed in the reaction? 4) 2Na 2 O2 (s) + 2H2O (l) → 4NaOH (s) + O2 (g) A) 63 B) -126 C) 7.8 D) 252 E) 3.9 5) The balanced net ionic equation for precipitation of CaCO3 when aqueous solutions of Na 2 CO3 and CaCl2 are mixed is __________. A) 2Na + (aq) + CO3 2- (aq) → Na 2 CO3 (aq) B) Na 2 CO3 (aq) + CaCl2 (aq) → 2NaCl (aq) + CaCO3 (s) C) Na + (aq) + Cl- (aq) → NaCl (aq) D) Ca2+ (aq) + CO 3 2- (aq) → CaCO3 (s) E) 2Na + (aq) + 2Cl- (aq) → 2NaCl (aq) 1 5) 6) The value of ΔH° for the reaction below is +128.1 kJ: 6) CH3OH (l) → CO (g) + 2H2 (g) How many kJ of heat are consumed when 4 mol of H2 (g) are formed as shown in the equation? A) 62.0 B) 128.1 C) 256.2 D) 326 E) 653 7) Of the following, which one is a state function? A) heat B) E C) w D) q E) none of the above 7) 8) When aqueous solutions of __________ are mixed, a precipitate forms. A) K 2 SO4 and CrCl3 8) B) KOH and Ba(NO3 )2 C) NaI and KBr D) Li2 CO3 and CsI E) NiBr2 and AgNO3 9) Specific heat is defined as heat transfered per gram per _________: A) unit energy B) degree Celsius C) unit work D) degree Fahreinheit 9) 10) When a system __________, ΔE is always negative. A) gives off heat and does work B) absorbs heat and has work done on it C) absorbs heat and does work D) gives off heat and has work done on it E) none of the above is always negative. 10) 11) Combining aqueous solutions of BaI2 and Na 2 SO4 produces a precipitate of BaSO4 . Which ion(s) 11) is/are spectator ions in the reaction? A) Ba 2+ and SO4 2B) Ba 2+ only C) SO4 2- and ID) Na + and IE) Na + only 2 12) With which of the following will nitrate ion form an insoluble salt? A) potassium ion B) sodium ion C) lead ion D) silver ion E) none of the above 12) 13) Calculate the value of ΔE in joules for a system that loses 50 J of heat and has 150 J of work performed on it by the surroundings. A) -100 B) 50 C) +200 D) 100 E) -200 13) 14) For which one of the following reactions is the value of ΔH°rxn equal to ΔHf° for the product? 14) A) 3Mg (s) + N2 (g) → Mg 3 N2 (s) B) 2C (graphite) + O2 (g) → 2CO (g) C) C2 H2 (g) + H2 (g) → C2H4 (g) D) C (diamond) + O2 (g) → CO2 (g) E) 2Ca (s) + O2 (g) → 2CaO (s) 15) Which one of the following compounds is insoluble in water? A) ZnS B) Na 2 CO3 C) Fe(NO3 )3 15) D) AgNO3 E) K 2 SO4 Answer: A 16) Which of the following are strong electrolytes? HCl C6 H12O6 16) NH3 KCl A) HCl, NH3 , KCl B) HCl, C6H12O6 , KCl C) HCl, C6H12O6 , NH3 , KCl D) HCl, KCl E) C6 H12O6 , KCl 17) Lithium does not occur in nature as Li (s) because __________. A) it is easily replaced by silver in its ores B) it is easily oxidized to Li+ C) it is easily reduced to LiD) it reacts with water with great difficulty E) it undergoes a disproportionation reaction to Li- and Li+ 3 17) 18) Which of the following is a statement of Hess's law? A) The ΔH of a reaction depends on the physical states of the reactants and products. B) The ΔH for a process in the forward direction is equal in magnitude and opposite in sign to the ΔH for the process in the reverse direction. C) The ΔH for a process in the forward direction is equal to the ΔH for the process in the reverse direction. D) If a reaction is carried out in a series of steps, the ΔH for the reaction will equal the product of the enthalpy changes for the individual steps. E) If a reaction is carried out in a series of steps, the ΔH for the reaction will equal the sum of the enthalpy changes for the individual steps. 18) 19) The balanced reaction between aqueous potassium hydroxide and aqueous sulfuric acid is __________. A) 2KOH (aq) + H2 SO4 (aq) → 2H 2 O (l) + K2SO4 ( aq) 19) B) 2KOH (aq) + H2 SO4 (aq) → KH2SO4 (aq) (aq) + O2 (g) C) 2KOH (aq) + H2 SO4 (aq) → K2 SO4 (aq) + 2H 2 (g) D) 2KOH (aq) + H2 SO4 (aq) → 2OH- (l) + HSO4 + (aq) (aq) + K (s) E) KOH (aq) + H2 SO4 (aq) → HOH2SO4 (aq) + K (s) 20) The combustion of ammonia in the presence of excess oxygen yields NO2 and H2 O: 20) 4 NH3 (g) + 7 O2 (g) → 4 NO2 (g) + 6 H2O (g) The combustion of 1.69 moles of ammonia consumes __________ moles of oxygen. A) .966 B) .0966 C) 11.83 D) 6.76 21) Of the species below, only __________ is NOT an electrolyte. A) Rb2 SO4 B) LiOH C) C6H12O6 E) 2.96 21) D) HCl 22) A strong electrolyte is one that __________ completely in solution. A) reacts B) decomposes C) ionizes E) KCl 22) D) disappears 23) How many milliliters of a stock solution of 11.1 M HNO3 would be needed to prepare 0.500 L of 0.500 M HNO3 ? A) 22.5 B) 2.78 C) 0.0444 4 D) 0.0225 E) 44.4 23) 24) The reaction 2Al2 O3 (s) → 4Al (s) + 3O2 (g) 24) ΔH° = 3351 kJ is __________, and therefore heat is __________ by the reaction. A) endothermic, absorbed B) exothermic, released C) exothermic, absorbed D) endothermic, released E) thermoneutral, neither released nor absorbed SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. 25) (3 pts) A base is defined as: 25) Answer: Something that increases the concentration of OH- ions. 5 26) (6 pts) If 294 grams of FeS2 is allowed to react with 176 grams of O2 according to the 26) following equation, how many grams of Fe2O3 are produced? FeS2 + O2 → Fe2 O3 + SO2 (NOT BALANCED) Answer: 160 27) (3 pts) Milk of magnesia (Mg(OH)2) is a cloudy white liquid because Mg(OH)2 is a ___________ in water. Answer: solid / precipitate 6 27) 28) (3 pts) If an equal number of moles of each of the following species were placed in water which would have the highest conductivity? CaCl2 , K2SO4, K3 PO4, C6 H12O6, PbCl2 28) Answer: K3PO4 29) (4 pts) The specific heat capacity of lead is 0.13 J/g-K. How much heat (in J) is required to raise the temperature of 15 g of lead from 22°C to 37°C? 29) Answer: 29 30) (3 pts) The value of ΔH° for the following reaction is -3351 kJ: 2Al (s) + 3O2 (g) → 2Al2O3 (s) The value of ΔHf° for Al2 O3 (s) is __________ kJ. Answer: -1676 7 30) 31) (4 pts) Calculate the oxidation number of P in each of the following : H3PO4 31) K3 PO2 Answer: 5, 1 32) (4 pts) The molarity (M) of an aqueous solution containing 52.5 g of sucrose (C12H22O11) in 35.5 mL of solution is __________. Answer: 4.32 8 32) 33) (6 pts) Using the activity series, which lists which metals get oxidized the easiest, determine if the following reactions will occur or not: A) Cu+2 (aq) + Mg(s) --> Cu(s) + Mg+2 (aq) YES B) Fe+2 (aq) + 2Ag(s) --> Fe(s) + 2Ag+ (aq) 33) NO C) Zn(s) + Ca+2 (aq) --> Zn+2 (aq) + Ca(s) NO 34) (3 pts) During the precipitation reactions demonstrated in class, Cu(OH)2 was a blue solid, Ni(OH)2 was a green solid and this metal preciptiated with I- to form a bright, paint-like yellow. What metal ion was used? Answer: Pb 9 34) 35) (4 pts) Given the following reactions 35) CaCO3 (s) → CaO (s) + CO2 (g) ΔH = 178.1 kJ C (s, graphite) + O2 (g) → CO2 (g) ΔH = -393.5 kJ the enthalpy of the reaction CaCO3 (s) → CaO (s) + C (s, graphite) + O2 (g) is __________ kJ. Answer: 571.6 36) (5 pts) The value of ΔH° for the reaction below is -336 kJ. Calculate the heat (kJ) released to the surroundings when 23.0 g of HCl is formed. CH4 (g) + 3Cl2 (g) → CHCl3 (l) + 3HCl (g) Answer: 70.7 10 36)