Vista College, Spring 2003

Spring 2016

Chem 1B Final Exam Review

1.Phosgene is a toxic gas prepared by the reaction of carbon monoxide and chlorine gases:

CO + Cl2  COCl2

The following data were obtained in a kinetic study of its formation:

Expt.#[CO]0, M[Cl2]0, MInitial Rate (mol.L–1.s–1)____

11.000.1001.29 x 10–29

20.1000.1001.33 x 10–30

30.1001.001.30 x 10–29

40.1000.01001.32 x 10–31



(a) Write the rate law for the formation of phosgene.

(b) Calculate the average value for the rate constant (k).

2.The following experimental data were obtained in a study of the reaction: 2HI(g) H2(g) + I2(g).

ExperimentTemperature (K)Initial [HI]Initial Rate (M/s)

17000.10 M1.8 x 10–5

27000.30 M1.6 x 10–4

38000.20 M3.9 x 10–3

48000.10 M ?

______

(a) Determine the rate law for the decomposition of HI and calculate the rate constant at 700 K and 800 K, respectively. (b) What is the initial rate at 800 K when [HI] = 0.10M. (c) Calculate the activation energy (Ea) for this reaction at 700 K.

3.The following reaction can be used to make H2 gas from methane and CO2 gas:

CH4(g) + CO2(g) ⇌ 2CO(g) + 2H2(g);

This reaction has Kp = 3.548 x 106 and 1200.K and Kp = 2.626 x 107 at 1300.K

(a) Calculate Kc for this reaction at 1200.K and 1300.K, respectively. (b) What is the percent yield of H2 when an equimolar mixture of CH4 and CO2 with a total pressure of 20.0 atm reaches equilibrium at 1200. K? (c) What is the percent yield of H2for this system at 1300. K? (d) Calculate H for this reaction.

4.An aqueous solution containing 1.105 g of potassium hydrogen phthalate (KHP = KHC8H4O4; molar mass = 204.22 g/mol) dissolved in 50.00 mL of solution is found to have pH = 3.20. (a) Determine the molar concentration of KHP and the pKa of phthalate ion (HC8H4O4–). (b) A 25.0-mL sample of this solution is titrated with NaOH of unknown concentration. If 20.40 mL of NaOH were required to reach equivalent point, what is the molar concentration of NaOH? (c) What is the molar concentration of the conjugate base, C8H4O42–, at equivalent-point? (d) Calculate the pH of the solution at equivalent-point?

5.A 50.0-mL solution of lactic acid, HC3H5O3, is titrated with 0.1965M NaOH, which requires 30.0mL of the base to reach the equivalent point. At equivalent point the solution is found to have pH = 8.36.

(a) Determine the molar concentration of lactic acid in the original solution and the concentration of lactate ions in the solution at equivalent point. (b) Calculate Kb for the lactate ion, C3H5O3-, and the Ka of lactic acid.

6. A phosphate buffer solution is prepared by dissolving 7.15 g of KH2PO4 and 17.85 g of K2HPO4 in 250.0 mL of solution. (a) Calculate the molar concentration of H2PO4– and HPO42–, respectively.

(b) Determine the pH of the solution. (H2PO4– has Ka = 6.3 x 10–8)

(c) If 0.010 mole of HCl is added to this buffer, what is the pH of the resulting solution? (Assume the solution volume remains the same.)

7.Predict whether solutions of the following salts are acidic, basic, or neutral.

(a) Sodium phosphate, Na3PO4.

(b) Sodium hydrogen sulfate, NaHSO4.

(d) Aluminum nitrate, Al(NO3)3.

(e) Ammonium sulfate, (NH4)2SO4 [Ka(NH4+) = 5.6 x 10-10; Kb(SO4-2) = 8.3 x 10-13]

8.Given the following reactions:

2 NO2(g)  2 NO(g) + O2(g);Ho = 112 kJ; So = 147 J/K

2 SO3(g)  2 SO2(g) + O2(g); Ho = 198 kJ; So = 187 J/K

(a) Calculate Ho, So and Go at 500.K for the reaction: SO2(g) + NO2(g)  SO3(g) + NO(g)

(b) What is the equilibrium constant, Kp, for this reaction at 500.K?

9.For the reaction: N2(g) + 3H2(g)  2NH3(g), Ho = -92 kJ and So = -199 J/K.

(a) Calculate Go at 25oC. (b) Determine whether the reaction, when carried out under standard conditions (partial pressure of each component in the mixture is 1 atm), is spontaneous at 227oC.

PH2 = 75 atm, PN2 = 25 atm, and PNH3 = 10. atm?

10.Draw Lewis structures for the following molecules; determine the hybridization on the central atom in each molecule; predict their molecular shapes, and indicate whether the molecule is polar or nonpolar.

(a) PF5(b) SF4 (c) ClF3(d) BrF5(e) XeF4

11.Write the Lewis structures for the following acids and predict their molecular shapes around the central atoms. (Note: all acidic hydrogen are bonded to the oxygen.)

(a) HClO2 (b) HClO3(c) HClO4 (d) H3PO4(e) H2SO4

12.Balance the following equations for the production of nitric acid in the Oswald process:

(i) __NH3(g) + __O2(g)  __NO(g) + __H2O(g)

(ii) __NO(g) + __O2(g)  __NO2(g);

(iii) __NO2(g) + __H2O(l)  __HNO3(g) + __NO(g);

(a) Use the balanced equation to determine the amount of nitric acid HNO3 that could be produced from 1.00 metric ton (1.00 x 103 kg) of ammonia. (Assume the reaction has 100% yields.) (b) If concentrated nitric acid contains 70.0% by mass of HNO3 and has density of 1.48 g/mL, how many gallons of concentrated nitric acid are produced from 1.00 metric ton of NH3 at 90.0% reaction yield?

(1 gall = 3.7854 L; 1 gallon of concentrated HNO3 weighs 5.60 kg)

13.The commercial bleach solution is prepared by the reaction of chlorine gas with dilute sodium hydroxide according to the following equation.

Cl2(g) + 2NaOH(aq)  NaOCl(aq) + NaCl(aq) + H2O(l)

If commercial bleach solution contains 5.25% (by mass) of NaOCl and the density of bleach solution is 1.06 g/mL, how many gallons of bleach can be produced from: (a) 1.00 m3 of Cl2, measured at STP; (b) 1.00 metric ton of Cl2. (Assume that NaOH is in excess.) (1 metric ton = 1000 kg)

14.Write the electron configuration and the orbital “box” diagram for each of the following ions using appropriate noble gas symbol to represent the inner-shell electrons. Indicate whether each ion is diamagnetic or paramagnetic.

(a) Cr3+:

(b) Mn2+:

(d) Ni2+:

(e) Zn2+ :

15.Name the following coordination compounds. Determine the oxidation state/number of the transition metal in each compound.

(a) [Ni(NH3)2Cl2)]

(b) K[Au(CN)4]

16.(i) Write Werner’s formula of each of the following coordination compounds. (ii) Draw the cis- and trans- structures of each compound.

(a) tetraamminediaquachromium(III) chloride

(b) Sodium tetrahydroxozincate(II)

17.A coordination compound is composed of 23.53% Co, 34.00% NH3 and 42.46% Cl, by mass.

(a) Determine the empirical formula of the compound in the form of Cox(NH3)yClz and calculate its molar mass. (b) When 2.15 g of this compound is dissolved in water and the solution is reacted with excess AgNO3, it yields 2.45 g of AgCl precipitate. Determine the mole ratio of AgCl to the compound and the number of moles of chloride ions that are counter ions. (c) Write the Werner’s formula of the compound and give the systematic nomenclature. (d) Write a balanced equation for the reaction of the compound with AgNO3 in aqueous solution.

18.Draw the structures of ALL possible isomers of complex ions with the molecular formula [Co(en)2(NO2)2]+. Indicate the pair of structures that are calssified as; (a) linkage isomers; (b) geometric isomers, and (c) optical isomers.

19.(a) Write the electron configuration and the orbital “box” diagram for Co3+ ion in its free form.

(b) Draw the crystal field energy diagram for the 3d-orbitals of Co3+: (i) in a weak-field, high spin octahedral complex ion [Co(H2O)6]3+; (ii) in a strong-field, low spin octahedral complex ion [Co(NH3)6]3+. Indicate whether each complex ion is diamagnetic or paramagnetic.

20.Explain the following observations using appropriate crystal field diagrams of d-orbitals.

(a) The complex ion tetrahydroxozincate(II), [Zn(OH)4]2–, is diamagnetic and the solution is colorless, whereas tetrahydroxochromate(III), [Cr(OH)4]–, is paramagnetic and its solution is green.

(b) The complex ion hexaaquacobalt(III), [Co(H2O)6]3+, is paramagnetic, while tris(ethylenediamine)cobalt(III) ion, [Co(en)3]3+, is diamagnetic.

(c) The compound sodium tetrachloronickelate(II), Na2[NiCl4], is paramagnetic, while potassium tetracyanonickelate(II), K2[Ni(CN)4], is diamagnetic.

21.A solution containing the complex ion [Co(H2O)6]2+ has a maximum absorption at 512 nm. Calculate the octahedral crystal field-splitting energy, (in kJ/mol), in [Co(H2O)6]2+. What is the color of solution containing this complex ion? Would you expect the complex ion [Co(NH3)6]2+ to absorb at longer or shorter wavelength region than [Co(H2O)6]2+? Explain your reasoning.

22.Draw structural formulas for all possible isomers of alkanes with molecular formula C6H14 and give their systematic names.

23.Name the following organic compounds:

(a) CH3CH2CH2CH2CHC≡CCH3

CH3

(b) CH3CH2CH2CH2CHCH2CH3

CH2Br

CH3C═CHCH3

(d) CH3CH2CHCHO

(e) CH3CH2CH2COOH

(f) (CH2)5C═O (a cyclic ketone)

(g) CH3–O–CH2CH3

(h) (CH3CH2)3N

O OH

║ │

(i) CH3C–OCH2CH2CH2CH2CH3(j) CH3CH2CHCH2CH3

(k) CH3(CH2)6CH2OH(l) CH3CONHCH3

24.Draw structural formula (in condensed or skeletal form) for each of the following organic compounds.

(a) 2,4-dinitrotoluene (b) cis-2,3-dichloro-2-butene

25.Write the structure of the organic products formed in each of the following reactions:

(a) CH3CH2CH3 + Cl2/uv  ?

(b) CH3CH═CH2 + HBr  ?

(d) C6H6 (benzene) + HNO3/H2SO4  ?

(e) C6H6 (benzene) + CH3Cl/AlCl3  ?

(f) CH3CH2CH2CH2OH + K2Cr2O7/H2SO4  ?

(g) CH3CH2CH-CH2OH + K2Cr2O7/H2SO4 

(h) CH3CH2CH2OH + conc. H2SO4/reflux 

Answers

1.(a) Rate = k[CO][Cl2]; (b) k = 1.31 x 10–28 L.mol–1.s–1.

2.(a) Rate = k[HI]2; k = 1.8 x 10–3 L.mol–1.s–1 at 700 K and = 9.8 x 10–2L.mol–1.s–1 L.mol–1.s–1 at 800 K;

(b) Rate = 9.8 x 10–4M/s; (c) Ea = 1.9 x 105 J/mol.

3.(a) Kp = 365.5 at 1200; Kp = 2305 at 1300; (b) 98.0%; (c) 99.0%; (d) 260. kJ/mol

4.(a) [HC8H4O4–] = 0.1082 M; pKa = 5.43; (b) [NaOH] = 0.1326 M; (c) [C8H4O42–] = 0.05958 M; (d) Kb = 2.7 x 10-9; pH at equivalent point = 9.10.

5.(a) [HC3H5O3] = 0.1179 M; [C3H5O3-] = 0.07369 M;

(b) Kb = 7.1 x 10–11; Ka = 1.4 x 10–4;

6.(a) [H2PO4–] = 0.210 M; [HPO42–] = 0.4099 M; (b) pH = 7.49; (c) pH = 7.37

7.(a) basic;(b) acidic;(c) neutral;(d) acidic;(e) acidic;

8.(a) H = -43 kJ;S = -20 J/K; G = -33 kJ;(b) Kp = 2.8 x 103

9.(a) Go = -33 kJ; (b) Go = +7.5 kJ  NOT spontaneous; (c) G = -41 kJ  spontaneous

12.(i) 4NH3(g) + 5 O2(g)  4NO(g) + 6 H2O(g)

(ii) 2 NO(g) + O2(g)  2 NO2(g);

(iii) 3 NO2(g) + H2O(l)  2HNO3(g) + NO(g);

(a) 2.47 x 106 g (2.47 x 103 kg); (b) 566 gallons;

13.(a) 15.8 gallons; (b) 4980 gallons

15.(a) Diamminedichloronickel(II)(b) Potassium tetracyanoaurate(III)

16.(a) [Cr(NH3)4(H2O)2]Cl3(b) Na2[Zn(OH)4](c) [Cu(H2O)2(en)2]SO4

17.(a) Empirical formula: Co(NH3)5Cl3; molar mass = 250.4 g/mol;

(b) 2 mol AgCl/mol Co(NH3)5Cl3;(c) [Co(NH3)5Cl]Cl2;

(d) [Co(NH3)5Cl]Cl2(aq) + 2AgNO3(aq)  2AgCl(s) + [Co(NH3)5Cl](NO3)2(aq)

21.Octahedral splitting energy, O = 234 kJ/mol

23.(a) 4-methyloctyne(b) 3-bromomethylheptane(c) 4-Ethyl-3-methylheptene

(d) Butanal(e) Butanoic acid(f) Cyclohexanone

(g) Ethylmethyl ether(h) Triethylamine(i) pentylacetate (or pentylethanoate)

(j) 3-Pentanol(k) 1-Octanol(l) N-methylacetamide (or N-methylethanamide)

25.(a) CH3CH2CH2Cl + CH3CHClCH3;(b) CH3CHBrCH3

(f) CH3CH2CH2COOH(g) CH3CH2COCOOH(h) CH3CH═CH2