Thermochemistry
Level 2
Serial Multiple Choice
The next 2 questions
relate to the information below:
I. C(s) + O2(g) à CO2(g) +
393.3 kJ; II.
CO(g) + 1/2 O2(g) à CO2
+ 282.8 kJ.
309. On the basis of the
information given in equation II and assuming no change in
temperature or pressure, one can correctly conclude that
1)
The rate of the reaction is rapid.
2) The total number of moles of product is
the same as the total number of moles
of reactants.
3) The reaction is exothermic.
4) The masses of the product is greater
than those of the reactants.
5) There will be an increase
in volume of reactants and products taken together as
the reaction proceeds.
ANS: 3
310. When 112 grams of CO are
used, which of the following occurs?
1) 1.0 mole of CO2 is produced.
2) 282.8 kJ of heat are generated. 4)
0.25 mole of CO2 is produced.
3) 2.0
moles of O2 are consumed. 5) 0.5 mole of O2 is
consumed.
ANS: 3
The next 2 questions deal with the following reactions:
I. Se(s)
+ O2(g) à SeO2(g); DH = -397.9 kJ
II.
Se(s) + 1.5 O2(g) à SeO3(g); DH = -297.1 kJ
III.
SeO2(g) + 1/2 O2(g) à SeO3(g).
311.
The heat of reaction, DH, for reaction III is:
1) –100.8 kJ; 2) +100.8 kJ; 3) –195.4 kJ; 4) +267.4 kJ; 5) –199.0 kJ.
ANS: 2
ANS: 2
312. Which statement about
these three reactions is false?
1) In each case, the heat content of the
reactants is greater than that of the products.
2) The first two reactions are exothermic,
the third is endothermic.
3) The potential energy of the reactants of
the third reaction is less than the product’s
potential energy.
4) The potential energy in
the product of the 1st reaction is less than the potential
energy in the
reactants of that reaction.
5) The kinetic energy in the reactants of
the 3rd reaction is greater than the product’s
kinetic energy.
ANS: 1
The next 3 questions
use the equations below:
I. C6H6(l) + __ O2(g) à ___ CO2(g) + __
H2O(l)
II. 6 C(s) + 3 H2(g) + 82.8
kJ à C6H6(l)
III. C(s) + O2(g) à CO2(g) +
393.3 kJ
IV. H2(g) + ½ O2(g) à H2O(l) +
285.8 kJ.
313. The heat of formation,
DH,
of 1 mole of C6H6(1) is:
1) –13.8 kJ; 2) –82.8 kJ; 3) +82.8 kJ; 4) –679.1 kJ; 5) +679.1 kJ.
ANS: 3
314. The coefficient for O2
in the combustion of 1 mole of C6H6(1) is
1) 5; 2) 7; 3) 7.5; 4) 15; 5) 9.
ANS: 3
315. The heat of combustion of one mole C6H6(l)
in equation I is obtained by combining
equations in which of the of
ways?
1) 6 III + 3 IV + II 3) 6 III - 3 IV + II
2) –6 IV + 3 IV + II 4) 6 III + 3 IV – II 5) 6 III + 6 IV + II
ANS: 4
The next 2 questions
relate to the following reactions
I. C(s) + O2(g) à CO2(g) + 393.3
kJ; II. CO(g) + 1/2
O2(g) à CO2(g) + 282.8
kJ.
316. On the basis of the information given in equation II and assuming no
change in
temperature or pressure, one
can correctly conclude that
1) the rate of the reaction is rapid.
2) the total number of moles of product is
the same as the total number of moles
of reactants.
3) the reaction is endothermic.
4) the mass of the product is greater than
those of the reactants.
5) none of these.
ANS: 5
317. When 224 grams of CO are consumed, which of the following occurs?
1) 1.0 mole of CO2 is produced.
2) 282.8 kJ of heat are
generated. 4) 4.0 moles of O2 are consumed.
3) 0.25 mole of CO2 is produced. 5) 16.0
grams of O2 are consumed.
ANS: 4
The next 2 questions relate to these balance equations:
I. N2 + O2 à 2 NO; DH = +180.7 kJ
I. N2 + O2 à 2 NO; DH = +180.7 kJ
II. N2 + 1/2 O2 à N2O; DH = +81.6 kJ
III. 2 N2O + O2 à 4 NO.
318. What is the value of DH for reaction III?
1) +17.6 kJ 2) +81.6
kJ 3) +198.3 kJ 4) +180.7 kJ 5) +120.1 kJ
ANS: 3
319. Which of these statements is incorrect?
1) The direct reaction of elements to form
N2O liberates heat.
2) The potential energy of NO is greater
than that of the elements from which it
was formed.
3) 90.4 kJ of heat would be needed if 16.0
grams of oxygen react according to
reaction I.
4) Some energy possessed by the NO is
associated with rotation of the molecules.
5) Use of a catalyst would not change the DH
values given in the equations.
ANS: 1
The next 3 questions refer to the following reactions:
I.
K(s) + 1/2 Br2(1) à KBr(s);
DH
= -393.3 kJ
II. K(s) + 1/2 Br2(g) à KBr(s); DH = -415.1 kJ.
II. K(s) + 1/2 Br2(g) à KBr(s); DH = -415.1 kJ.
320. Which of the following statements about reaction I is wrong?
1) Heat content of product is less than
that of reactants.
2) For each mole of KBr(s) formed, 393.3 kJ
of heat is lost.
3) The reaction is exothermic.
4) Potential energy of reactants is less
than that of products.
5) none of these.
ANS: 4
321. The difference between the two heats of
reaction, +21.8 kJ, is
1) the heat required to melt one mole of
KBr.
2) the heat released when two moles of
KBr(s) form.
3) the heat required to vaporize 1/2 mole
of liquid Br2.
4) the heat released in the overall
reaction.
5) probably due to errors in measurement.
ANS: 3
322. The formation of 71.4 grams of KBr(s) in reaction II is accompanied
by the release
of 1) 21.8 kJ; 2) 124.7 kJ; 3) 249.4 kJ; 4) 1380.7 kJ; 5) 3,550.0 kJ.
ANS: 3
ANS: 3
The next 3 questions deal with potential energy diagrams
below. These graphs
present two reaction paths for the same overall reaction A à D.
323. The total heat of reaction, DH,
for reaction A à D By Reaction Path I is
1) -10 kJ; 2) +10 kJ; 3) +40 kJ; 4) +50 kJ; 5) -70 kJ.
ANS: 2
324. The
activation energy, DH‡, in reaction step B à C for the reaction on Path I
is
1) -15 kJ; 2) +20 kJ; 3) +40 kJ; 4) +50 kJ; 5) none of these.
ANS: 2
325.
Concerning Reaction Path I, which of the following is false?
1) At equilibrium both products C and D
will be present.
2) B is considered to be an intermediate
product.
3) The total reaction A à D is
exothermic.
4) X, Y and Z are points where activated
complexes are formed.
5) The slowest step in the reaction A à D is
probably A à B.
ANS: 3
The next 3 questions
refer to the diagram below.
Substance A reacts to form D by two reaction paths.
326. The overall heat of reaction for Reaction Path II, A à D is:
1) 70 kJ; 2) 45 kJ; 3) 10 kJ; 4) –5 kJ; 5) –20 kJ.
ANS: 4
327. The activation energy for the reaction step X à D is:
1) 45 kJ; 2) 35 kJ; 3) 15 kJ; 4) 0 kJ; 5) –15 kJ.
ANS: 2
328. Select the statement that is wrong concerning Reaction
Path II:
1) Removing heat from the reacting system
would favor the formation of D.
2) Product X has a higher heat content than
product D.
3) Reaction
A à X is
endothermic.
4) The overall reaction A à .D is exothermic.
5) Activated complexes are represented by
points W, X, V and D.
ANS: 5
The next
2 questions refer to the
following reactions:
I. S(s) + O2(g) à SO2(g); DH = -297.1 kJ.
II. S(s) + 1.5 O2(g) à SO3(g); DH = -397.9 kJ.
SO2(g) may
be oxidized to SO3(g) as shown in the following equation:
III. SO2(g) + 0.5
O2(g ) à SO3(g).
329. The heat of reaction, ΔH, for reaction III is
1) –100.8 kJ; 2) +100.8 kJ; 3) –195.4 kJ; 4) +267.4 kJ; 5) 328.9 kJ.
ANS: 1
330. Which statement about these three reactions is wrong?
1) In each
case, the heat content of reactants is greater than that of products.
2) All
three reactions are exothermic.
3) The
potential energy of the reactants in the third reaction is less than the P.E.
of the
products.
4) The P.E.
in the product of the 1st
reaction is less than the P.E. in the reactants.
5) The
kinetic energy in the reactants of the 3rd reaction is less than the K.E. in
the
products.
ANS: 3
The next 2 questions are concerned with factors influencing the
rate of reaction.
331. Raising the temperature of a reacting system
increases the rate of the reaction,
but does not
increase the:
1)
activation energy.
2) average
velocity of the reacting particles.
3)
vibrational motions within the molecules.
4) number
of collisions.
5) fraction of reacting particles which
possess energies greater than the activation energy.
ANS: 1
332. Reaction rates are also affected by
concentration, collision geometry, and the
presence of
a catalyst. Which is false
concerning these factors?
1) A
catalyst lowers the activation energy requirement.
2) A
reaction occurs each time particles of the reactants collide.
3)
Increasing the concentration of reacting particles increases the collision
chances.
4) The
slowest reaction involved in a reaction mechanism determines the rate
of the
overall reaction.
5) none of
these.
ANS: 2
The next 3 questions are
concerned with the following reactions:
A. H2(g) + Cl2(g) à 2 HC1(g)
+ energy C. 92U238 à 2He4 + 90Th234 +
energy
B. C12(g)
à C12(l) +
energy D.
Li+(g) + Cl-(g) à LiCl(s)
+ energy
E. none of these equations
333. Of the above reactions, the one involving the smallest
amount of energy per mole
is reaction 1) A; 2) B; 3) C; 4) D; 5) E.
ANS: 2
334. Which one of the following statements is wrong?
1)
Reaction B is a phase change.
2) In all the reactions above, the product
has less enthalpy than the reactant.
3) All of the reactions are exothermic.
4) All of the reactions move toward lower
potential energy as the reactions occur.
5) Atoms are conserved in all of the
reactions.
ANS: 5
335. The amount of energy
stored as nuclear energy changes during the course of
reaction(s) 1) C only; 2) A & C; 3) B & D; 4) A, C & D; 5) E.
ANS: 1
ANS: 1
The next 2 questions
involve the two potential energy diagrams. The graphs
present two reaction paths for the same overall reaction A à D.
336. Comparing Reaction Paths I
and II, which one of the following statements is wrong?
1) Path I could indicate the operation of a
catalyst.
2)
Reaction II would probably be a slower reaction.
3) In both I and II, the forward reaction
proceeds simultaneously with the reverse one.
4) Reaction Path II does not involve the
formation of an activated complex.
5) none of these.
ANS: 4
337. Concerning Reaction Path I, which one of the following statements is
false?
1) At equilibrium both products C and D
will be present.
2) X, Y and Z represent points at
which activated complexes are formed.
3) B is considered to be an intermediate
product.
4) The slowest step in the reaction A à D is probably
A à B.
5) The total reaction A à D is exothermic.
ANS: 5
The next 3 questions
refer to the evaporation of water.
Water evaporates spontaneous,
and has been found by experiment to absorb 2.26 kJ/gram in
the process.
338. DH
for the reaction H2O(l) à H2O(g), as calculated from the above data, is:
1) 2.26 kJ/mole. 3) 40.6 kJ/mole.
2) 12.6 kJ/mole. 4) 75.3 kJ/mole. 5) 225.9 kJ/mole.
2) 12.6 kJ/mole. 4) 75.3 kJ/mole. 5) 225.9 kJ/mole.
ANS: 3
339. A potential energy diagram that could represent
the reaction H2O(l) à H2O(g)
is
1) 1; 2) 2; 3) 3; 4) 4; 5) 5.
ANS: 5
340. A potential energy diagram that could represent the reaction H2O(g) à H2O(l)
is
1) 1; 2) 2; 3) 3; 4) 4; 5) 5.
ANS: 4
For the next 3 questions: The following graph illustrates a Potential
Energy
diagram for the reaction Br + H2 à
.HBr +
H.
341. Which interval on the graph corresponds to the heat
of reaction for the above
reactions? 1) A 2) B 3) C 4) D 5) B minus A
ANS: 4
342. The activation energy for
HBr + H à Br + H2 is given by
1) A; 2) B; 3) C; 4) D; 5) B plus C.
ANS: 1
343. Raising the temperature of the system would
1) decrease only rate of forward
reaction.
2) decrease only rate of reverse
reaction. 4) decrease rates of both
reverse reactions.
3) increase only rate of forward
reaction. 5) increase rates of both
reverse reactions.
ANS: 5
The next 3 questions
relate to the graph which represents two possible
reaction paths for the reaction:
Heat + 2 NH3(g) à N2(g) + 3 H2(g).
344. The smal1est activation energy shown for the decomposition
of NH3 corresponds
to the interval labeled
1) A; 2) B; 3) C; 4) D; 5) E.
ANS: 2
345. One can correctly conclude from the above graph that the heat of
the reaction
corresponds to the interval
labeled
1) A; 2) B; 3) C; 4) D; 5) E.
ANS: 1
346. The largest activation energy shown for the production
of NH3 corresponds
to the interval labeled
1) A; 2) B; 3) C; 4) D; 5) E.
ANS: 4
The next 2 questions refer to the following curve:
347. Point A on the kinetic energy distribution curve represents the
minimum energy
requirement
for the formation of an activated complex.
If the temperature of
the system is reduced,
1) point A moves to the left. 3) point A does not
move.
2) point A moves to the right. 4) no prediction can be made.
5) point A moves only slightly to left.
2) point A moves to the right. 4) no prediction can be made.
5) point A moves only slightly to left.
ANS: 3
348. If a catalyst is introduced into the system
1) point A moves to the left. 3) point A does not move.
2) point A moves to the right. 4) no prediction can be made.
5) point A moves only slightly to right.
ANS: 1
For the next 4 questions: The potential energy path made by a complex
chemical
reaction is illustrated in the diagram below.
349. Which step illustrates a spontaneous endothermic reaction?
1) 1 2) 2 3) 3 4) 4 5) 5 6) 6 7) 7
ANS: 7
350. Which step does not belong in the reaction mechanism?
1) 1 2) 2 3) 3 4) 4 5) 5 6) 6 7) 7
ANS: 2
351. Which step will be the rate determining step?
1) 1 2) 2 3) 3 4) 4 5) 5 6) 6 7) 7
ANS: 5
352. Which step is an exothermic reaction with medium speed?
1) 1 2) 2 3) 3 4) 4 5) 5 6) 6 7) 7
ANS: 4
For the next 4 questions: The diagram illustrates the potential energy
path made by
a complex chemical reaction. The
reaction mechanism is shown below.
353. Which step illustrates a spontaneous exothermic reaction?
1) 1 2) 2 3) 3 4) 4 5) 5 6) 6 7) 7
ANS: 1
354. Which step will be the rate determining step?
1) 1 2) 2 3) 3 4) 4 5) 5 6) 6 7) 7
ANS: 6
355. Which step does not belong in the reaction mechanism?
1) 1 2) 2 3) 3 4) 4 5) 5 6) 6 7) 7
ANS: 4
356. Which step is an endothermic reaction with medium speed?
1) 1 2) 2 3) 3 4) 4 5) 5 6) 6 7) 7
ANS: 3
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