Third Exam Form A Key 1 B 2 D 3 A 4 B 5 C 6 C 7 D 8 B 9 D 10 C 11 E 12 A 13 A 14 C 15 D 16 C 17 B 18 C 19 D 20 8 mol 21 Mg NO3 2 s Mg2 aq 2 NO31 aq 1 mol 119 0 g 0 275 L 6 50 g x 22 M 23 not graded 24 2000 kJ a Br2 g Cl2 g 2 BrCl g BrCl 2 K Br2 Cl2 b 2 KClO3 s 2 KCl s 3 O2 g K O2 3 Copyright North Carolina State University 1 Select the true statement regarding cubic unit cells A The face centered cubic has the largest number of atoms and the least packing efficiency B The face centered cubic has the largest number of atoms and the greatest packing efficiency C The simple cubic has the smallest number of atoms and the greatest packing efficiency D The simple cubic has the largest number of atoms and the greatest packing efficiency E The body centered cubic has the smallest number of atoms and the least packing efficiency 2 The unit cell shown at the right is of the mineral Chromatite which is made of chromium ions white spheres and oxide ions black spheres Note there is a black sphere on each face and white spheres at the corners and in the body of the cell What is the chemical formula of this compound A CrO B CrO2 C Cr2O D Cr2O3 E Cr3O2 3 In the diagram at the right identify the insulator 4 Note the following melting points all of these elements are considered to be non metals SiC 2700 oC AsI3 146 oC SeO2 118 oC Ge 1137 oC In their solid state how many of these materials would be covalent solids A 1 B 2 C 3 D 4 E 0 5 Select the best statement regarding bonding between molecules or ions in solids A The bonding in ionic solids is much weaker than in covalent or molecular solids B The bonding in covalent and molecular solids is much weaker than in ionic solids C The bonding in molecular solids is much weaker than in covalent or ionic solids D The bonding in covalent and ionic solids is much weaker than in molecular solids E The bonding in covalent solids is much weaker than in molecular or ionic solids For the next two questions consider the following materials A CH3OH B Br2 C KCl D C2H6 E NH3 6 Select the material with the highest melting point 7 Select the material with the lowest melting point Copyright North Carolina State University 8 When water freezes A the value of H is negative and the value of S is positive B the value of H is negative and the value of S is negative C the value of H is positive and the value of S is positive D the value of H is positive and the value of S is negative 9 Select the FALSE statement concerning a system and its surroundings A When the system absorbs heat E of the system is positive B When work is done by the system E of the surroundings is positive C When the system releases heat E of the surroundings is positive D When work is done on the system E of the system is negative 10 Consider the following reaction PCl5 g PCl3 g Cl2 g If this reaction is endothermic what can you say about the spontaneity A The reaction is spontaneous at both low and high temperature B The reaction is spontaneous at low temperature but non spontaneous at high temperature C The reaction is non spontaneous at low temperature but spontaneous at high temperature D The reaction is non spontaneous at both low and high temperature 11 What is the difference between G and Go A G includes entropy Go does not B Go is specifically for 0 oC G is for unspecified temperature C for a given reaction they will be of opposite signs D G gives the spontaneity of a reaction Go does not E Go is for specific amounts of reactant and product G is for unspecified amounts 12 Given this reaction A g B g If starting with equal concentrations of A and B the rate of the forward reaction is greater than the rate of the reverse reaction then when the system reaches equilibrium A K 1 B K 1 C K 1 13 Given this reaction C g D g o If G is positive for this reaction then A The activation energy for the forward reaction is larger than for the reverse reaction B The activation energy for the forward reaction is smaller than for the reverse reaction C The activation energy for the forward reaction is equal to that for the reverse reaction Copyright North Carolina State University 14 Given this reaction E g F g If the value of K is 100 for this reaction then A The value of Go will be positive B The value of Go will be zero C The value of Go will be negative 15 Given the reaction energy diagram shown at the right you can conclude that A the reaction is endothermic and increasing the temperature will increase the amount of product B the reaction is endothermic and increasing the temperature will increase the amount of reactant C the reaction is exothermic and increasing the temperature will increase the amount of product D the reaction is exothermic and increasing the temperature will increase the amount of reactant 16 Given the following reaction CS2 4 H2 CH4 2 H2S If CS2 is removed from the system you should expect A the amount of H2 to decrease and the amount of CH4 to increase B the amount of H2 to increase and the amount of CH4 to increase C the amount of H2 to increase and the amount of CH4 to decrease D the amount of H2 to decrease and the amount of CH4 to decrease 17 During a reaction a weaker bond breaks and a stronger bond forms This reaction is most likely A endothermic B exothermic Use the phase diagram of material X shown at the right to answer the following two questions P atm 18 At 100 oC and 0 4 atm pressure X is a A solid B liquid C gas D supercritical fluid 1 0 4 19 At 60 oC if the pressure is raised from 0 8 atm to 1 2 atm X will A melt B sublime C condense 50 60 D freeze GO ON TO THE NEXT PAGE PLACE YOUR ANSWERS FOR 20 24 DIRECTLY ON THIS EXAM Copyright North Carolina State University 180 E boil T oC 20 8 Consider the following balanced equation 2 C2H2 5 O2 4 CO2 2 H2O If 6 moles of C2H2 react with 10 moles of O2 how many moles of CO2 can be formed Answer 21 10 Write a balanced equation for dissolving magnesium nitrate in water Include states of matter 22 10 SET UP this problem 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