MCT 1 Junior Freshman 2000/01

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UNIVERSITY OF DUBLIN

TRINITY COLLEGE

FACULTY OF SCIENCE

Department of Chemistry

Junior Freshman Annual Trinity Term, 2004

Multiple Choice Test

Wednesday 19 May RDS 14.00 - 16.00

Chemistry Paper II

Answer All questions

The use of Log Tables is permitted.

A Periodic Table giving Atomic Weights etc., and a Table of fundamental constants is attached.

INSTRUCTIONS

1. Using a soft pencil (grade B or softer) complete sections A, B, C and D on the Computer Answer Form. Write your student number in Section D as well as marking the number on the form by filling in the box with a clear thick horizontal line (not a Ö, X or 0).

GOOD BAD BAD BAD BAD

2. Answer each question by first marking on the question paper the answer that you think is appropriate. Do not mark more than one answer to each question. In questions with numerical answers, mark the answer closest to yours, if you do not get exactly any of those given.

3. Carefully transfer your answers to the Computer Answer Form. If you make a mistake, rub it out with a CLEAN eraser and enter the correct answer. Use only a soft pencil and mark your answers with a clear thick horizontal line. Failure to do this could result in the misreading of your form. Do not write comments on the form.

4. When you have finished, make sure your name, student number and seat number are on the Computer Answer Form and hand it up to the invigilator. Do not in any way tear, crumple or deface the form. This form is the only record of your answers.

5. There will be no negative marking for this exam.

1. The mass (in grams) of FeSO4 ·7H2O required for preparation of 125 mL of 0.90 M solution is:

(a) 16 g

(b) 25 g

(d) 13 g

(e) 43 g

Correct Answer (c)

2. Which assignment of oxidation number is incorrect for the underlined element?

(a) K2Cr2O7; +6

(b) SeO32-; +4

(d) NH3; +3

(e) Cu(NO3)2; +2

Correct Answer (d)

3. What is the standard enthalpy change for the reaction:

2NOCl (g) ® N2 (g) + O2 (g) + Cl2 (g).

Given that:

½ N2 (g) + ½ O2 (g) ® NO (g) DH = +90 kJ

NO (g) + ½ Cl2 ® NOCl (g) DH = -40kJ

(a) -100 kJ

(b) -130 kJ

(d) +1005 kJ

(e) +170 kJ

Correct Answer (a)

4. Consider two identical flasks containing equal masses of gas: the first contains pure Ar, the second pure He. Unless otherwise indicated assume the temperature is the same for both. Identify which of the following statements are incorrect.

(i) There are equal numbers of molecules in each flask.

(ii) The molecules in the Ar flask have a lower average kinetic energy.

(iii) The molecular mean free path is larger in the Ar flask.

(iv) The pressure is higher in the Ar flask.

(v) The pressure in both flasks can be made equal by heating the Ar flask.

(a) (i) and (ii)

(b) (i), (ii) and (iii)

(d) (i), (iii) and (v)

(e) (ii), (iii) and (v)

Correct Answer (c)

5. Consider a thermodynamic process in which a drop of water evaporates to form water vapour. Identify which of the following statements are correct.

(i) The entropy of the system has increased.

(ii) The entropy of the surroundings has increased.

(iii) The entropy on the universe has increased.

(iv) Heat was transferred from the surroundings to the system.

(v) The free energy of the system has increased.

(a) (i) and (iii)

(b) (ii) and (iii)

(d) (i), (iii) and (iv)

(e) (ii), (iii) and (v)

Correct Answer (d)

6. Deuterons (a deuteron is a nucleus consisting of a proton-neutron pair) in a beam are travelling with a uniform velocity of 990.4 m s-1.

They have a wavelength of:

(a) 2.00 ´ 10-10 m

(b) 4.00 ´ 10-12 m

(d) 4.00 ´ 10-8 m

(e) 2.00 ´ 10-6 m

Correct Answer (a)

7. Which combination of answers is correct?

The Mn3+ ion:

(i) has a greater number of unpaired electrons than Cr2+

(ii) has the same number of unpaired electrons as Cr2+

(iii) has the same number of unpaired electrons as neutral Mn

(iv) can lose an electron to create an ion with a greater spin

(v) can lose an electron to create an ion with the same spin as Co2+.

(a) (i) and (iv)

(b) (ii) and (v)

(d) (iii) only

(e) (ii) and (iii)

Correct Answer (b)

8. Which one of the following statements about the carbon dioxide molecule is true?

(a) the electron pair lobes on the central atom are tetrahedral, resulting in a bond angle of about 109°

(b) the electron pair lobes on the central atom are trigonal, resulting in a bond angle of about 120°

(d) the molecular structure is linear

(e) the central atom has an expanded octet.

Correct Answer (d)

9. The molecular orbital description of F2+ shows that the molecular ion:

(i) is paramagnetic

(ii) could lose an electron to produce a half-filled molecular orbital

(iii) could lose an electron to produce an ion whose total spin is the same as that of a N2 molecule

(iv) has a bond order which is greater than that of F2

(v) has a bond order which is less than that of O2.

(a) (i) only

(b) (i) and (ii)

(d) (v) only

(e) (i), (ii), (iv) and (v)

Correct Answer (e)

10. For the salt AgCl the lattice enthalpy is -916 kJ mol-1 and the sum of the hydration enthalpies of the ions is -832 kJ mol-1. Which of the following statements are correct.

(i) DH for solution = + 84 kJ mol-1
(ii) DH for solution = –1748 kJ mol-1
(iii) the solubility of AgCl in water decreases with temperature
(iv) AgCl is only sparingly soluble.

(a) all
(b) (i) and (iv) only
(c) (ii) and (iv) only
(d) (ii) and (iii) only
(e) None

Correct Answer (b)

11. For the reaction

2NO + 2H2 → N2 + 2H2O

the following data was obtained:

[NO] [H2] Rate

(mol dm-3) (mol dm-3) (mol dm-3 s-1)

5 x 10-3 2 x 10-3 2.4 x 10-5

10 x 10-3 2 x 10-3 9.6 x 10-5

5 x 10-3 4 x 10-3 4.8 x 10-5

10 x 10-3 4 x 10-3 19.2 x 10-5

The rate (mol dm-3 s-1) of reaction is:

(a) 24 [NO][H2]

(b) 480 [NO]2[H2]

(d) 48 [NO]2[H2]2

(e) 2400 [NO]

Correct Answer (b)

12. The rate of the reaction:

A+B2 → AB + B

is directly proportional to the concentration of B2 but independent of A.

Which of the following statements is correct?

(a) The reaction obeys second order kinetics

(b) The mechanism involves a single bimolecular reaction step

B2 → 2B slow

B + A → AB fast

(d) The mechanism may be

A + B2 → AB2 slow

AB2 → AB + B fast

Correct Answer (c)

13. Which of the following statement(s) is /are incorrect?

(i) If two liquids A and B undergo ideal mixing ∆H mixing = 0

(ii) In the above case, ∆G mixing = - T∆S mixing

(iii) The vapour pressure above an ideal solution of two liquids A and B will be equal to xAPAo + xBPBo, where xA and xB are the mole fractions of A and B and PAo and PBo are their standard vapour pressures

(iv) All solutions exhibit ideal behaviour if sufficiently dilute

(a) all

(b) (i) and (iii) only

(d) (ii) only

(e) (iv) only

Error in question

14. Electrophilic addition of bromine to cyclohexene yields:

(a) cis-1,2-dibromocyclohexane

(b) cis-1,1-dibromocyclohexane

(d) trans-1,1-dibromocyclohexane

(e) trans-1,3-dibromocyclohexane

Correct Answer (c)

15. The reaction of 2-chloropropane with cyanide ion is:

(a) first order

(b) second order

(d) a free-radical reaction

(e) none of the above

Correct Answer (b)

16. Which of the following is the strongest acid?

(a) ethanoic acid

(b) 4-methylbenzoic acid

(d) 2,2-dichloroethanoic acid

(e) carbonic acid

Correct Answer (d)
17. Alkoxide ions react with alkyl halides to give:

(a) ethers

(b) esters

(d) alcohols

(e) alkanes

Correct Answer (a)

18. The reaction of but-1-yne with aqueous acid in the presence of Hg2+ ions gives:

(a) but-1-ene

(b) butan-2-ol

(d) butan-2-one

(e) butanal

Correct Answer (d)

19. A nucleophile should possess:

(a) an overall positive charge

(b) an unpaired electron and a positive charge

(d) a lone pair of electrons

(e) no charge

Correct Answer (d)

20. Which one of the following compounds contains the greatest number of sp2 hybridised carbon atoms?

(a) phenylethene

(b) phenylethyne

(d) cyclohexanol

(e) ethane

Correct Answer (a)

21. The correct IUPAC name for the following compound is:

(a) 4,5,5-trimethylpent-1-ene

(b) 4-methyl-4-isopropylbut-1-ene

(d) 2,4-dimethylhex-5-ene

(e) 4-isopropyl-4-methylbut-1-ene

Correct Answer (d)

22. The dominant product from the reaction between propene and HCl is:

(a) 1-chloropropane

(b) 2-chloropropane

(d) 1-chloropropane and 2-chloropropane are formed in equal amounts

(e) propyne

Correct Answer (b)

23. Hydrolysis of a carboxylic ester using aqueous sodium hydroxide gives:

(a) a sodium carboxylate and an alcohol

(b) a carboxylic acid and a sodium alkoxide

(d) a carboxylic ether

(e) a carbocyclic triol

Correct Answer (a)

24. Reaction of a primary aliphatic amine with aqueous nitrous acid gives:

(a) an amide

(b) a nitro compound

(d) an alcohol

(e) a nitrile

Correct Answer (d)

25. For a solution labelled 0.2 M barium hydroxide, which of the following is correct?

(a) [OH- ] = 0.4 M ; [Ba2+] = 0.2 M

(b) [OH- ] = 0.2 M ; [Ba2+] = 0.1 M

(d) [OH- ] = 0.4 M ; [Ba2+] = 0.4 M

(e) [OH- ] = 0.2 M ; [Ba2+] = 0.2 M.

Correct Answer (a)
26. A buffer solution contains 0.5 M acetic acid (Ka = 1.8 x 10–5) and 0.5 M sodium acetate. The pH of the solution is :

(a) 4.74

(b) 1.00

(d) 3.74

(e) There is not enough information provided to solve the problem.

Correct Answer (a)

27. The standard potential of the cell is 0.35 V at 298 K. If the standard potential of the Pb, Pb2+ couple is – 0.13 V, calculate the standard potential of the Ag/AgCl, Cl– couple.

(a) – 0.22 V

(b) 0.48 V

(d) 0.22 V

(e) – 0.35 V.

Correct Answer (d)

28. Given :

Which is the strongest reducing agent ?

(a) Cu

(b) Fe2+

(d) Ag

(e) Cu2+.

Correct Answer (e)

29. From the description below, what is the most probable identity of E?

‘The element E is a monoatomic gas which reacts with O2 and F2 only. The formation of EF2 (linear), EF4 (square planar) and EF6 occurs on reaction of F2 with E under different conditions.’

E is :

(a) Hydrogen

(b) Helium

(d) Sulfur

(e) Xenon

Correct Answer (e)

30. The mineral corundum is aluminium oxide Al2O3. Corundum gemstones can have different colours because of:

(a) the presence of organic impurities

(b) the presence of silicate ions

(d) the presence of water of crystallization

(e) particulate matter trapped in the oxide

Correct Answer (c)

31. These two elements have a diagonal relationship. They exhibit the electrical properties of semiconductors. The elements and their oxoanions occur in extended covalent networks. Both elements form acidic hydroxides. These elements are:

(a) silicon and boron

(b) lithium and magnesium

(d) iron and copper

(e) carbon and sulfur

Correct Answer (a)

32. Salts of this metal element are present in seawater and have an important biological role. The metal ion is involved in phosphate metabolism and is present in chlorophyll. Salts of this metal are used in the treatment of indigestion and constipation.

The identity of the metal element is:

(a) copper

(b) magnesium

(d) lithium

(e) barium

Correct Answer (b)

Department of Chemistry

Use the following values for fundamental constants, conversion factors, atomic masses and other data for examination purposes:

Constants

Gas Constant / R = 8.314 J K-1 mol-1
(R = 8.206 ´ 10-2 L atm K-1 mol-1)
Boltzmann’s Constant / kB = 1.381 ´ 10-23 J K-1
Planck’s Constant / h = 6.626 ´ 10-34 J s
 = h/2p = 1.055 ´ 10-34 J s
Velocity of light / c = 2.998 ´ 108 m s-1
Charge of electron / e = -1.602 ´ 10-19 C
Rest mass of electron / me = 9.109 ´ 10-31 kg
Rest mass of proton / mp = 1.673 ´ 10-27 kg
Vacuum permittivity / eo = 8.854 ´ 10-12 J-1 C2 m-1
Vacuum permeability / mo = 4p ´ 10-7 J s2 C-2 m-1
Bohr magneton / b = 9.274 ´ 10-24 J T-1
Nuclear magneton / bn = 5.051 ´ 10-27 J T-1
Rydberg constant / R¥ = 2.178 ´ 10-18 J = 1.097 ´ 105 cm-1
Avogadro’s constant / NA = 6.022 ´ 1023 mol-1
Faraday constant / F = NAe = 9.648 ´ 104 C mol-1
Bohr radius / ao = 5.292 ´ 10-11 m
Molar volume at S.T.P. / Mv = 22.414 dm3 mol-1
Conversion factors etc.
1 eV = 1.602 ´ 10-19 J = 9.648 ´ 104 J mol-1
1 cm-1 = 1.986 ´ 10-23 J = 11.96 J mol-1 = 1.240 ´ 10-4 eV
1 Å = 0.1 nm = 10-10 m
1 standard atmosphere = 1.013 ´ 105 N m-2 (Pa) = 760 torr = 1013 mbar
1 L = 1 dm3 = 10-3 m3
1 Debye (D) = 3.336 ´ 10-30 C m
1 calorie = 4.184 J
1 L atm = 101.34 J

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