AnswersChemistry Credit Recovery BEnthalpy of Reaction

Enthalpy of Reaction — Unit test Answers

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A reaction occurs when solid X is placed into solution Y. As a result, the temperature of the new solution increases by 3°C. The temperature rises another 2°C when more of solid X is added to the solution. What does this indicate about the effect of adding more solid?

A
It increased the number of molecular collisions.
B
It decreased the number of molecular collisions.
C
It decreased the space between the molecules and lowered the reaction rate.
D
It increased the space between the molecules and increased the reaction rate.
2
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According to Le Chatelier’s principle, what happens when the concentration of reactants is doubled in a chemical reaction that was in equilibrium?

A
The equilibrium shifts to the right to favor the formation of products.
B
The equilibrium shifts to the left to favor the formation of reactants.
C
The equilibrium is unaffected by the increase in concentration.
D
The equilibrium is lost because the concentrations have been disturbed.
3

Consider the chemical equilibrium of a soap that is present in its aqueous solution. C17H35COONa(aq) C17H35COO–(aq) + Na+(aq)sodium stearate (soap) stearate ion What will happen if a large quantity of NaCl is added to the aqueous solution?

Question illustration
A
The equilibrium will shift to the right, favoring the dissociation of soap in aqueous solution.
B
The equilibrium will shift to the left to such an extent that it leads to the precipitation of solid soap.
C
The equilibrium will not be affected by the addition of NaCl to the solution.
D
The equilibrium will be permanently destroyed by the addition of NaCl.
4

Which statement best applies collision theory to preventing a dangerous reaction from occurring?

A
Store the reactants together at a low pressure.
B
Keep all sparks or flames away from the reactants.
C
Store the reactants together at a low temperature.
D
Keep the reactants in separate containers.
5

Which will not appear in the equilibrium constant expression for the reaction below?

Question illustration
A
[H2O]
B
[C]
C
[H2]
D
[CO]
6

Consider the reaction.When does the given chemical system reach dynamic equilibrium?

Question illustration
A
when the forward and reverse reactions stop
B
when the rate of the forward reaction is higher than the rate of the reverse reaction
C
when the concentration of the reactants is higher than the concentration of the products
D
when the rates of the forward and reverse reactions are equal
7

Consider the equation below.What is the equilibrium constant expression for the given reaction?

Question illustration
A
K subscript e q equals StartFraction bracket upper C a upper O EndBracket over upper C a upper C upper O subscript 3 EndBracket EndFraction.
Option A
B
K subscript e q equals StartFraction StartBracket upper C upper O subscript 2 EndBracket StartBracket upper C a upper O EndBracket over StartBracket upper C a upper C upper O subscript 3 EndBracket EndFraction.
Option B
C
K subscript e q equals StartBracket upper C upper O subscript 2 EndBracket.
Option C
D
K subscript e q equals StartFraction 1 over StartBracket upper C upper O subscript 2 EndBracket EndFraction.
Option D
8

Which energy graph represents the nonspontaneous transition of graphite into diamond?

A
A graph with Reaction progression on the horizontal axis and energy on the vertical axis. A line starts low on the vertical axis, runs briefly parallel to the horizontal axis, slopes up sharply, curves down a short distance, and levels out.
Option A
B
A graph with Reaction progression on the horizontal axis and energy on the vertical axis. A line starts midway up the vertical axis, runs briefly parallel to the horizontal axis, slopes up sharply, curves down sharply, and levels out below the initial starting point.
Option B
C
A graph with Reaction progression on the horizontal axis and energy on the vertical axis. A line starts midway up the vertical axis, runs briefly parallel to the horizontal axis, slopes up a small amount, then curves down to level out below the initial starting point.
Option C
D
A graph with Reaction progression on the horizontal axis and energy on the vertical axis. A line starts midway up the vertical axis, runs briefly parallel to the horizontal axis, slopes up a moderate amount, then curves down sharply to level out below the initial starting point.
Option D
9

Consider the following equation in chemical equilibrium. C2H4(g) + H2(g) C2H6(g) + 137 kJ What happens to the amount of ethane (C2H6) when the temperature of the system is increased?

Question illustration
A
The amount of ethane decreases.
B
The amount of ethane increases initially and then decreases.
C
The amount of ethane increases.
D
The amount of ethane decreases initially and then increases.
10

The dissociation of a weak electrolyte is suppressed when

A
a strong electrolyte with a common ion is added to the weak electrolyte solution.
B
a strong salt is dissolved with the weak electrolyte solution.
C
a strong electrolyte with a different ion than the weak electrolyte is added.
D
the strong electrolyte solidifies in the presence of the weak electrolyte.
11

What happens as the activation energy increases?

A
The pressure of the system decreases.
B
The kinetic energy of colliding molecules changes.
C
The reactant surface area decreases.
D
The reaction begins to slow down.
12

Consider the following reversible reaction.What is the equilibrium constant expression for the given system?

Question illustration
A
K e q equals StartFraction StartBracket upper C upper O EndBracket StartBracket upper H 2 EndBracket superscript 2 over StartBracket upper C upper H subscript 3 upper O upper H EndBracket EndFraction.
Option A
B
K e q equals StartFraction StartBracket upper C upper H subscript 3 upper H upper O EndBracket over StartBracket upper C upper O EndBracket StartBracket upper H 2 EndBracket superscript 2 EndFraction.
Option B
C
K e q equals StartFraction StartBracket upper C upper O EndBracket StartBracket upper H 2 EndBracket over StartBracket upper C upper H subscript 3 upper O upper H EndBracket EndFraction.
Option C
D
K e q equals sart fraction StartBracket upper C upper H subscript 3 upper O StartBracket upper C upper O EndBracket StartBracket upper H 2 EndBracket EndFraction.
Option D
13

Which applies to the collision theory?

A
Particles need to collide in order to react.
B
Particles may obtain successful collisions in any molecular orientation.
C
Temperature increase causes kinetic energy of particles to decrease.
D
Reactions do not have to begin with collision of molecules or particles.
14

A solid reactant is placed into a beaker of a warm water. The liquid vigorously bubbles as the solid dissolves into the solution. What will most likely happen if the temperature of the liquid is slightly reduced?

A
More bubbles will be produced because the solution is becoming more concentrated.
B
Fewer bubbles will be produced because of fewer collisions of reactant molecules.
C
The solid will get smaller at a faster rate because of more collisions of reactant molecules.
D
The solid will get larger at a slower rate because precipitate is coming out of the solution.
15

Which term refers to the speed at which reactants are converted into products?

A
reaction rate
B
activation energy
C
meta stable state
D
spontaneous reaction
16

Consider the following chemical reaction at equilibrium. H2SO4(aq) 2H+(aq) + SO42–(aq) The addition of which compound will cause a shift in equilibrium because of a common ion effect?

Question illustration
A
NaCl
B
KNO3
C
MgSO4
D
FeCl3
17

A change in which factor will affect the rate of reaction only when gases are involved?

A
temperature
B
pressure
C
surface area
D
concentration
18

The production of water proceeds according to the following equation.2H2(g) + O2(g) 2H2O(g)Which describes a way to speed up the collisions between hydrogen and oxygen molecules to produce more water?

Question illustration
A
Use a less-intense source of heat on the reactants.
B
Maintain the same temperature of the reactants.
C
Place the reactants in a smaller container.
D
Reduce the concentration of the reactants.
19

The reaction below is at dynamic equilibrium.Which statement is true for the equilibrium system?

Question illustration
A
The concentration of NH3 is greater than the concentration of N2.
B
The concentration of NH3 equals the concentration of N2.
C
The rate of the forward reaction equals the rate of the reverse reaction.
D
The rate of the forward reaction is greater than the rate of the reverse reaction.
20

Which best explains why sawdust burns more quickly than a block of wood of equal mass under the same conditions?

A
The molecules move more quickly in the sawdust than in the block of wood.
B
The pressure of oxygen is greater on the sawdust.
C
More molecules in the sawdust can collide with oxygen molecules.
D
Oxygen is more concentrated near the sawdust than the block of wood.

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