' General Chemistry ( j i . ) Final Exam (6.25.15)

1-30 : 3 points; 29-32 : as indicated.

1. The balaneed equation for the reaction of bromate ion with bromide in acidic solution is given by;

BrO . + 5Br- + 6H+ 3Br2 + 3H2O

At a particular instant in time, the value o f - A [ B r - ] / A / is 2.0 x IQ-^ mol/L • s. What is the value of A[Br2]/A/ in the same units?

(a)6.0x 10-3, (b) 3.3 ^ 10-3, (c) 2.0 x i o - 3 , ( d ) 1.2 x 10-3, (e) 3.3 x IQ-^.

A 2. The reaction o f (CH3)3CBr with hydroxide ion proceeds with the formation o f (CH3)3COH.

^ (CH3)3CBr(aq) + OH-(aq) ^ (CH3)3COH(aq) + Br-(aq)

The following data were obtained at 55°C.

[(CH3)3CBr]o [ O H - ] o Initial Rate Exp. (mol/L) (mol/L) (mol/L s)

1 0.10 0.10 1.0 X 10-3 2 0.20 0.10 2.0 X 10-3 3 0.10 0.20 1.0 X 10-3 4 0.30 0.20 ?

What will the initial rate (in mol/L • s) be in Experiment 4?

(a) 3.0 X 10-3, (b) 6.0 x 10-3, (c) 9.0 x 10-3, (d) 18 x 10-3, (g) none of these.

3. Tabulated below are initial rate data for the reaction

2Fe(CN)63- + 2 | - -> 2Fc(CN)64- + I2

Initial

Run [Fe(CN)63-]Q [I-JQ [Fe(CN)64-]o l i2]0 Rate (M/s) 1 0.01 0.01 0.01 0.01 1 X 10-5 2 0.01 0.02 0.01 0.01 2 x 10-5 3 0.02 0.02 0.01 0.01 8 x 10-5 4 0.02 0.02 0.02 0.01 8 x 10-5 5 0.02 0.02 0.02 0.02 8 X 10-5

The experimental rate law is;

(a) d[l2]/dt = ^[Fe(CN)63-]2[i-]2[Fe(CN)64-]2[l2]

(b) d[l2]/dt - A[Fe(CN)63-]2[I-][Fe(CN)64-][i2]

(c) d[l2]/dt = /:[Fe(CN)63-)j2[i-]

(d) d[ l2 ] /d t - / : [Fe(CN)63-][ I - ]2

(c) d[l2]/dt = A[Fe(CN)63-][l-][Fe(CN)64-]

4. The reaction

2A + B ^ C

has the following proposed mechanism:

S t e p l : A + B D (fast equilibrium)

Step2:D + B ^ E

Step3:E + A - ^ C + B

I f step 2 is the rate-determining step, then the rate of formation of C should equal:

(a) A[A], (b) A[A]2[B], (c) A[A]2[B]2, (d) A[A][B], (e) k[A][B]2.

_ — : 5. The reaction 2 N 0 ^ N2 + O2 has the following rate law: - d [ N O ] / d t - 2 A [ N O ] 2 .

After a period of 2.0 x 10^ s, the concentration of NO falls from an initial value of 2.8 x I0~3 mol/L to 2.0 x 10-3 mol/L. What is the rate constant, k?

(a)7.2x ] 0 - 2 M - V s , ( b ) 1.7x 10"^ M- ' /s , (c)4.0x l O ^ M - ^ / s , (d) 4.0 x I Q - ^ M - V s , (e)3.6x 10-2M-1/S.

6. The following data were collected for the decay of HO2 radicals:

Time [HO2] Time [HO2I Os l .Ox l O l l molec/cm3 14 s 1.25 x 10^0 molec/cm3 2 s 5.0 X lOlO moiec/cm3 30 s 6.225 xlO^ molec/cm3 6 s 2.5 X 10 * molec/cm3

Which of the following statements is true?

(a) The decay of HO2 occurs by a first-order process. (b) The half-life of the reaction is 2 ms. (c) A plot of In [HO2] versus time is linear with a slope of-k. (d) The rate o f the reaction increases with time. (e) A plot of 1/[H02] versus time gives a straight line.

7-8. The reaction

2N0Br -> 2N0 + Br2 exhibits the rate law

Rate = /:[N0Br]2 - - d[NOBr]/dt

where k= 1.0 x 10-5 . g- l 25°C. This reaction is run where the initial concentration of NOBr ([NOBrJo) is TOO x I Q - l M .

7. What is one half-life for this experiment?

(a) 5.0 X 10-' s, (b) 6.9 X 10^ s, (c) l .Ox 10-5 s, (d) l.Ox 10^ s, (e) none of these.

_ / A _ 8. The [NO] after 1.00 hour has passed is

(a) 3.5 X 10-^ M, (b) 9.9 x 10-3 M, (c) 9.7 x 10-3 M, (d) 1.0 x 10-3 M , (e) none ofthese.

9. The reaction 2 N 0 + O2 —> 2NO2 obeys the rate law

-d[02]/dt = Aobsd[NO]2[02].

Which of the following mechanisms is consistent with the experimental rate law?

(a) N O + N O N2O2 (slow) N2O2 + O2 2NO2 (fast)

( b ) N 0 + 02 NO3 (fast equilibrium) NO3 + NO ^ 2NO2 (slow)

2

(c) 2N0 =5=^ N2O2 (fast equilibrium) N2O2 NO2 + O (slow) NO + O -> NO2 (fast)

(d) O2 + O2 -> O2 + O2* (slow) O2 + NO ^ NO2 + O (fast) 0 + N 0 - » N 0 2 (fast)

(e) none o f these

CA 10. The reaction 2NO2 2N0 + O2 obeys the rate law

d[O2 ] /dt - .1 .40x 10-2 [N02]2 at 500. K.

I f lhe initial concentration o f NO2 is TOO M , how long w i l l it take for the [NO2] to decrease to 25.0% of its initial value?

(a) 49.5 s, (b) 71.4 s, (c) 214 s, (d) 1.40 x 10-2 s, (g) cannot be determined from this data.

11. The elementary chemical reaction

0 + C I 0 ^ C l + 02

is made pseudo-first order in oxygen atoms by using a large excess o f CIO radicals. The rate constant for the reaction is 3.5 x \0~^ I cm^/molecule • s. I f the initial concentration o f CIO is 1.0 x 10^ I molecules/cm^, how long wi l l it take for the oxygen atoms to decrease to 10.% of their initial concentration?

(a) 2.4 s, (b) 0.017 s, (c) 3.2 x 10^3 s, (d) 0.66 s, (e) 23 s.

*) 12. Which of the following would you expect to have the highest boiling point?

(a) F2, (b) CI2, (c) Br2, (d) I2, (e) A l l of these have the same boiling point.

13. Which o f the following is the correct order of boiling points for KNO3, CH3OH, C2H6, Ne?

(a)~Ne < CH3OH < C2H6 < 1<:N03 (b) KNO3 < CH3OH < C2H6 < Ne

(c) Ne < C2H6 < KNO3 < CH3OH

(d) Ne < C2H6 < CH3OH < KNO3

(e) C2H6 < Ne < CH3OH < KNO3.

14. In which o f the following groups of substances would dispersion forces be the only significant factors in determining boiling points?

I . CI2 I I . HF I I I . Ne IV. KNO2 V. CCI4

(a) I , in, V, (b) I , I I , I I I , (c) I I , IV, (d) I I , V, (e) HI, IV, V.

15. Which one o f the following statements about solid Cu (face-centered cubic unit cell) is incQirfect?

(a) It wil l conduct electricity. (b) There are two atoms per unit cell. (c) The number of atoms surrounding each Cu atom is 12. (d) The solid has a cubic closest-packed structure. (e) The length o f a face diagonal is four times the Cu radius.

3

> !6. Sodium oxide (Na20) crystallizes in a structure in which the O-^" ions are in a face-centered cubic lattice and the Na"*" ions arc in tctrahcdral holes. The number of Na"*" ions in the unit cell is:

(a) 2, (b) 4, (c) 6, (d) 8, (e) none ofthese.

7. Aluminum metal crystallizes in a face-centered cubic structure. The relationship between the radius of an A l atom (r) and the length of an edge of the unit cell (£) is:

(a) r = Ell, (b) r = (y/2/4) E, (c) /• = (^3/4) E, (d) r = 2 £ , (e) r = 4 £ .

0 18. A metal crystallizes in a body-centered unit cell with an edge length of 2.00 x 10^ pm. Assume the atoms in the cell touch along the cube diagonal. The percentage of empty volume in the unit cell wi l l be:

(a) 0%, (b) 26.0%, (c) 32.0%, (d) 68.0%, (e) none ofthese. i

11 9. I f equal, rigid spheres are arranged in a simple cubic lattice in the usual way, i.e., in such a way that they touch each other, what fraction of the corresponding solid wi l l be empty space? [The volume of a sphere is (4/3)7rr3, with TT = 3.14.]

(a) 0.52, (b) 0.32, (c) 0.68, (d) 0.48, (e) none ofthese.

C\, 20. Doping Se with As would produce a{n) semiconductor with conductivity compared to pure Se.

(a) /7-typc, increased, (b) rt-type, decreased, (c) /?-type, increased, (d) /?-type, decreased, (e) intrinsic, identical.

CA 31 • Which metal ion has a electron configuration?

(a) Pd2+, (b) Ag+, (c) Fe3+ (d) Os2+, (e) Co2+.

22. A coordination compound of Cu2+ can be described as Cu(NM3);,.S04 and is known to contain 29.9% NH3 (Cu = 63.5). The value of x is:

(a) 2, (b) 3, (c) 4, (d) 6, (e) none ofthese.

0 23. Which of the following complexes shows geometric isomerism?

(a) [Co(NH3)5CI]S04, (b) [Co(NH3)6]Cl3, (c) [Co(NH3)5Cl]Cl2, (d) K[Co(NH3)2Cl4], (e) none ofthese.

ex hibits? 24. What IS the sum of the geometric and optical isomers that the complex ion Co(en)2Cl2'

(a) 0, (b) l , ( c ) 2 , (d)3, (e)4.

25. For the process Co(NH3)5Cl2+ + C I " Co(NH3)4Cl2"^ NI-I3 what would be the ratio of cA to trans isomer in the product?

(a) 1 : l , ( b ) l :2 , (c) 1 : 4, (d) 4 : 1, (e) 2 : I .

A_ 26. Which of the following is paramagnetic?

(a) Zn(H20)62+, (b) Co(NH3)63+ (strong field), (c) Cu(CN)32- (d) Mn(CN)62- (strong field), (e) none of these.

27. Which of the following complexes can exhibit optical isomerism? (en = H 2 N — C H 2 — C H 2 — N H 2 and is bidentale)

(a) c/.v-Co(NH3)4Cl2, (b) lrans-Co{QX\)2Bt2, (c) cf9-Co(en)2Cl2, (d) Co(NH3)3Cl3, (e) none ofthese.

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28. For which o f the following metal ions would there be no low-spin versus high-spin distinction in octahedral complexes?

(a) Cr2+ (b) V2+, (c) Fc3+, (d) Mn2+, (c) Co3+.

29-30. Consider the following complexes:

I . Pt(NH3)2Cl2 (square planar)

I I . Rh (en)32+ (en - H 2 N — C I I 2 — C H 2 — N H 2 and is bidentate)

I I I . CoCl42-(tetrahedrai)

f~\ 29. The complex(es) having geometrical {cis-trans) isomers, but not optical isomers is (are);

(a) I , (b) I I , (c) HI, (d) I , I I , (e) I , I I , i l l . ^ ^ ^ ^ A ^^^fhe complex(es) having optical isomers, but not^^l^a! isomers is (are):

(a) I , (b) I I , (c) I I I , (d) I , I I , (e) I , I I , I i r ~ ~ ~ "

31. The unit cell for a pure xenon fluoride compound is shown in the following QFQ-— diagram. •

(a) What is the formula of the compound?

(b) The unit cell of the xenon fluoride compound has a height of 702 pm, and the edge of the square base has a length o f 432 pm. Calculate the density o f the xenon fluoride compound. (Xe = 131.3, F - 19.0).^(6£oints)

*

1 -ludriiii;

1 T

=^^A.( A *A? cfbm (fHb) tllbn does O2. / ^ ^ ^

A A - ^ 3 x K ; ^

33. Carbon monoxide is toxic because it binds more slilpngly to iron in he;rlog Consider the following reactions and approximate standard free energy changes: /c'^-i ^

Hb + O2 Hb02 AG^' - -70 kJ A • Hb + C O - ^ H b C O A G ° - - 8 0 k J

Using these data, estimate the equilibrium constant value at 25°C for the following reaction:. (8 points)

Hb02 + CO <=> HbCO + O.

I 4 k 0 ^ — 7 h U % ^A-dAop)

z f —{AT^PO T

33. Consider the following data: Co^^ + e ^ C o ' ^ 1.82 V

CoCen)3^^ K f = 1.5 x lO'^

Co(en)3- ' K f = 2 . 0 x lO'*^

where en = ethylenediamine.

(a) Calculate E° for the half-reaction Co(en)3^^ + e' ^ Co(en)3"^

(b) Based on your answer to part (a), which is the stronger oxidizing agent, Co^^ or Co(en)3-'''?

(c) Use the crystal field mode! tojationalize the result in part (b). (8 points)

CcA , - ^ ( ^ \ ^ _ A=u3A Co(A—^ZV4 fC "? (X?S_)

A Ac (X2v

QAJ -^y JMl U^vi, J / ^ - 2.0 5(10 '

CA:( \A. > eiA3^5 U^ = (x ' 3

U) -1>

2,

/ u-

^ 1 3

34. Consider the reaction 3A + B-KC D + E

where the rate law is defined as -d[A]/dr = k[AJ'[B][C].

An experiment is carried out whe.e [B],) = [C]o = 1.00 M and [A]o = t .OO x 10"* M

(a) I f after 3.00 minutes, [A] - 3.26 x 10 ' M , calculate the value of k.

(b) Calculate the half-life for this experiment.

(c) Calculate the concentration of B and the concentration of A after 10.0 minutes. (8 points)

^A[>i<A3a%Cc), xA--AftAj(c)-AA' ' ' ^ ^ '3-

% b ^ > f T 1 S^ ' VXiC-WT , >

r^^^(c) A A - .F^FzAf! A^

_ ^ ^ , • \ , V Uvwt'V ( j27n:#3 ^ ^

CA) ^ i ' i t Ay -wr Lv^V'y-^^P t ^

1 ^ A ^ ^ ^ y A M - l > n v x M^yfe^^^yz^ .1 $.3 AF AA = V1 3TXX