4. Based on the following thermochemical equation below, which statement is false? 2 NH 3 (g) N 2 (g) + 3 H 2 (g) H = kj

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1 CHEM 101 WINTER EXAM 3 On the answer sheet (Scantron) write you name, student ID number, and recitation section number. Choose the best (most correct) answer for each question and enter it on your answer sheet. 1. Please choose the letter a as your answer for this question. Avogadro s Number: mol -1 q = m c ΔT Specific Heat of Water = J g -1 C In the reaction below, when 7.6 g of CS 2 reacts with an excess of chlorine gas, 28.3 kj of heat is produced. Calculate ΔH for the reaction. CS 2 (l) + 3 Cl 2 (g) CCl 4 (l) + S 2 Cl 2 (l) a. 76 kj b. 163 kj c. 283 kj d. 215 kj e. 215 kj 3. In the reaction shown in the above question, when 7.6 g of CS 2 reacts with an excess of chlorine gas, 28.3 kj of heat is produced. If this reaction is carried out in a calorimeter with a heat capacity of 626 J/ C and also containing 1750 g of water, what is the value for ΔT? a C b C c C d C e C 4. Based on the following thermochemical equation below, which statement is false? 2 NH 3 (g) N 2 (g) + 3 H 2 (g) H = kj a. For the reverse process, H = kj. b. The value of kj applies to the formation of two moles of NH 3. c. The value of kj applies to the formation of two moles of H 2 and six moles of N 2. d. Per mole of N 2 produced, H = kj. e. Per mole of H 2 produced, H = kj. 5. Determine the heat of reaction for the process PbS(s) + 3/2 O 2 (g) + C(s) Pb(s) + SO 2 (g) + CO(g) using the information given below: PbS(s) + 3/2 O 2 (g) PbO(s) + SO 2 (g) H = kj Pb(s) + CO(g) PbO(s) + C(s) H = kj a kj b kj c kj d kj e kj

2 6. The standard enthalpies of formation for several substances are given below: CO(g) kj/mol CO 2 (g) kj/mol H 2 O(l) kj/mol H 2 O(g) kj/mol H 2 O 2 (l) kj/mol CH 3 OH(g) kj/mol C 2 H 5 OH(l) kj/mol C 2 H 5 OH(g) kj/mol Determine the molar heat of condensation for C 2 H 5 OH. a kj b kj c kj d kj e kj 7. The standard enthalpies of formation for several substances are given below: CO 2 (g) kj/mol H 2 O(g) kj/mol CH 3 OH(g) kj/mol C 2 H 2 (g) kj/mol Calculate the H for the following reaction that takes place when an oxyacetylene welding torch is used. C 2 H 2 (g) + 5/2 O 2 (g) 2 CO 2 (g) + H 2 O(g) a kj b. 802.kJ c kj d kj e kj 8. A best fuel is characterized by a. low fuel value and low energy density b. high fuel value and high energy density c. weak bonds in the fuel and weaker bonds in the combustion products d. strong bonds in the fuel and weak bonds in the combustion products e. fuel and oxidation products having bonds of identical strength 9. Which statement concerning the interaction between two atoms is false? a. If two atoms are widely separated, there is very little attraction between them. b. When two atoms are one bond length apart, the electrons on one atom are attracted to the nucleus of the other atom. c. When two atoms have very little separation between them, electron repulsion occurs. d. A covalent bond occurs when two or more electrons are shared between two atoms. e. As atoms get extremely close to one another, their electrons attract each other. 10. Which statement about covalent bonds is false? a. Covalent bonds allow atoms to achieve a filled outermost electron shell. b. Covalent bonds are very stable and unreactive. c. Covalent bonds occur in molecular compounds. d. Covalent bonds involve the sharing of valence electrons. e. Covalent bonds are found in organic molecules.

3 11. Which element will have five electrons in its Lewis symbol? a. aluminum b. silicon c. sulfur d. phosphorus e. gallium 12. How many electrons will be in the correctly drawn Lewis Structure for chloroform, CHCl 3? a. 32 b. 44 c. 26 d. 24 e Which of the following statements could not describe a covalent bond? a. The sharing of eight electrons between two atoms b. The sharing of four electrons between two atoms c. A single bond between a carbon atom and a phosphorus atom d. The sharing of two or more electrons equally between two atoms e. The sharing of two or more electrons unequally between two atoms 14. Determine the number of electrons that the four elements below require in order to achieve an octet of electrons. carbon nitrogen bromine oxygen a b c d e Which statement about hydrocarbons is false? a. Hydrocarbons can be aliphatic or aromatic. b. Methane, a saturated alkane, is the simplest hydrocarbon. c. Saturated hydrocarbons contain only C H and C C single covalent bonds. d. Hydrocarbons contain mostly carbon and hydrogen, but frequently also contain other elements such as oxygen and sulfur. e. Hydrocarbons can be straight chain, branched chain, or cyclic structures. 16. Which molecule does not contain a multiple bond? a. C 2 H 6 b. HCN c. CCl 2 O d. CO 2 e. N Draw the correct Lewis dot structure for CFBrICl. Which statement correctly describes the structure? a. The structure contains 4 single bonds, 2 double bonds, and 12 lone pairs. b. The structure contains 1 single bond, 2 double bonds, one triple bond and 32 lone pairs. c. The structure contains 2 single bonds, no double bond, and 2 lone pairs. d. The structure contains 2 single bonds, 1 double bond and 8 lone pairs. e. The structure contains 4 single bonds, no multiple bonds, and 12 lone pairs.

4 18. Assume all hydrocarbons shown are linear. Which compound contains a triple bond? a. C 3 H 6 b. C 18 H 38 c. C 3 H 4 d. C 2 H 6 e. C 5 H Which of the following compounds cannot exhibit cis-trans isomerism? a. CBrCl=CFI b. CClH=CHI c. H 2 C=O d. Cl 2 C=CBr 2 e. c and d 20. Which bond is strongest? a. carbon nitrogen triple bond b. carbon nitrogen double bond c. carbon hydrogen bond d. carbon oxygen triple bond e. carbon carbon single bond 21. Which bond is most polar? a. H C b. H N c. H H d. H F e. H O 22. Of the elements shown, which is the most electronegative? a. sulfur b. iodine c. nitrogen d. oxygen e. carbon 23. What is the formal charge on each carbon atom in ethane, H 3 C CH 3? a. 2 b. 1 c. 0 d. +1 e Which of the following species does not have resonance structures? a. CO b. SO 2 c. CH 4 d. NO e. O 3

5 25. Draw the Lewis dot structure for BeCl 2. Which of the following statements best describes this structure? a. It obeys the octet rule on all atoms. b. It has less than an octet on at least one atom. c. It has no lone pairs of electrons on the chlorine atoms. d. It has less than an octet of electrons on all atoms. e. It exceeds the octet rule. 26. A list of non-metals is given below. In which set of elements is each atom capable of exceeding the octet rule? B Si N P O S F Cl a. Si, P, S, Cl b. F, N, O, B c. O, S, F, Cl d. B, Si, N, P e. All eight elements can exceed the octet rule.