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PSC: Chemistry > Chemical Reactions: Energy, Rates and Equilibrium > Flashcards

Chemical Reactions: Energy, Rates and Equilibrium Flashcards

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1
Q

Does the following describe kinetic or potential energy?

Water at the top of a waterfall.

A

Potential.

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2
Q

Does the following describe kinetic or potential energy?

Kicking a ball.

A

Kinetic.

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3
Q

Does the following describe potential or kinetic energy?

The energy in a Cliff energy bar.

A

Potential.

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4
Q

Does the following describe kinetic or potential energy?

A skier at the top of a hill.

A

Potential.

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5
Q

When looking at energy transfer, which 2 parts of the universe are we studying?

A

System and surroundings.

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6
Q

What is the mathematical definition of internal energy?

A

Sum of kinetic energy and potential energy.

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7
Q

True or False:
An exothermic reaction causes heat to flow out of the SYSTEM while an endothermic reaction causes heat to flow into the system.

A

True.

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8
Q

Is the following reaction exothermic or endothermic?

a reaction releases 550 kJ of heat.

A

Exothermic.

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9
Q

Is the following reaction exothermic or endothermic?

The energy of the products is greater than the energy of the reactants.

A

Endothermic.

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10
Q

Is the following reaction exothermic or endothermic?

The metabolism of glucose provides energy to the body.

A

Exothermic.

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11
Q

Is the following chemical reaction exothermic or endothermic?

CH4 + 2O2 → CO2 + 2H2O + 802 kJ

A

Exothermic.

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12
Q

Is the following chemical reaction exothermic or endothermic?

Ca(OH)2 + 65.3 kJ → CaO + H2O

A

Endothermic.

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13
Q

Consider the reaction shown:

C3H8 + 5 O2 → 3 CO2 + 4 H2O + 488 kcal

We can say that this reaction is ________ and that the sign of ΔH is ________.

A

Exothermic; Negative.

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14
Q

To simplify comparisons, the energy value of fuels is expressed in units of…

A

kcal/g.

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15
Q

Is the following reaction exothermic or endothermic?

The energy of the products is greater than the energy of the reactants.

A

Endothermic.

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16
Q

Consider the reaction shown:

304.0 kcal + 4 PCl3(l) → P4(s) + 6 Cl2(g)

When 50.00 g of PCl3 react, ________ kcal will be ________.

A

27.67; consumed.

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17
Q

How many kJ will be released if it requires 3.5 mol of oxygen to combust a certain amount of methane?

CH4 + 2O2 → CO2 + 2H2O + 802 kJ

A

1404 KJ

1) Divide 3.5/2 = 1.75
2) Multiply the heat amount by that #

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18
Q

Consider the reaction shown:

N2 + O2 → 2 NO ΔH = 43.2 kcal

When 50.0g of N2 react, ________ kcal will be ________.

A

77.1 kcal; consumed.

(Go from g -> mol -> kcal)

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19
Q

For the following chemical reaction, how much energy would be released 2.54 g of aluminum reacted with excess iron(III) oxide?

2Al + Fe2O3 → Al2O3 + 2Fe + 850 kJ

A

40 KJ.

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20
Q

How much heat is released during
the combustion of methane using the given bond dissociation energies:

        CH4 + 2 O2 → CO2 + 2H2O

Number and types of bonds in each molecule:

CH4 (4 C-H bonds); O2 (1 O=O); CO2 (2 C=O bonds); H2O (2 O-H bonds).

Bond dissociation energies:

C-C (347 kJ/mol); C-H (413 kJ/mol);
O=O (498 kJ/mol; C=O (799 kJ/mol); O-H (467 kJ/mol)

A
  • 818 KJ.
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21
Q

True or False: All exothermic reactions are spontaneous.

A

False.

Exothermic reactions are more likely to be spontaneous, but not all are.

22
Q

What states of enthalpy and entropy favors spontaneity as it relates to a chemical reaction?

A

-ΔH, +ΔS.

23
Q

True or False:
A positive value for ΔG correlates to a spontaneous reaction.

A

False, a negative value of ΔG correlates with a spontaneous reaction.

ΔG = free energy change.

24
Q

True or False:
To obtain the value of ΔG for a reverse reaction, multiply the forward reaction by -1.

A

True.

25
Q

For a reaction occurring at 25°C, the value of ΔH is determined to be 10.5 kJ and the ΔS is 30 J/K. What is the value of ΔG in joules? Is this reaction spontaneous at this
temperature?

A

1560 J; Non-spontaneous.

26
Q

For a reaction occurring at 25°C, the value of ΔH is determined to be 1.8 kJ and the ΔS is 113 J/K. What is the value of ΔG in joules? Is this reaction spontaneous at this temperature?

A

–31891 J; Spontaneous.

27
Q

True or False: A negative ΔG corresponds to an exergonic reaction.

A

True.

28
Q

“The minimum energy required for a reaction to occur” is the definition of:

A

Activation energy.

29
Q

In order for a reaction to occur, particle must do these 2 things…

A

(1) Collide and (2) be in the correct orientation.

30
Q

True or false:
Reaction rates are not determined by
a speed up or increase in energy.

A

True.

Reaction rates are determined by the orientation, and activation energy.

31
Q

A rapid reaction is distinguished by…

A

Having a small value of activation energy.

32
Q

For a chemical reaction to occur, all of the following must happen except:

A) a large enough number of collisions must occur.

B) reactant particles must collide with the correct orientation.

C) reactant particles must collide with enough energy for change to occur.

D) chemical bonds in the reactants must break.

A

A) a large enough number of collisions must occur.

33
Q

How would adding more SO2 change the rate of the following reaction:

2SO2 + O2 → 2SO3

A

Increase; speed up.

34
Q

How would increasing the temperature change the rate of the following reaction:

2SO2 + O2 → 2SO3

A

Increase; speed up.

35
Q

How would adding a catalyst change the rate of the following reaction:

2SO2 + O2 → 2SO3

A

Increase; speed up.

36
Q

How would removing some of the O2 change the rate of the following reaction:

2SO2 + O2 → 2SO3

A

Decrease; slow it down.

37
Q

How would adding SO3 change the rate of the following reaction:

2SO2 + O2 → 2SO3

A

Decrease; slow it down.

38
Q

In a chemical equilibrium what can be said about both directions of the reaction?

A

The forward and reverse reactions are occurring at the same rate.

39
Q

In order to determine if a reaction
is at equilibrium what must be true about the products and reactants?

A

The rate at which the forward and reverse reactions are proceeding are equal.

40
Q

Calculate the equilibrium constant for the reaction below if a tank was found to contain 0.106 M O2, 0.00652 M SO3, and 0.00129 M SO2.

2 SO3(g) <–>2 SO2(g) + O2(g)

A

4.14 × 10^-3

41
Q

Calculate the equilibrium constant for the reaction below if a tank was found to contain 0.205 M O2, 0.0552 M SO3, and 0.0829 M SO2.

        2 SO3(g) <-->2 SO2(g) + O2(g)
A

0.462

42
Q

Calculate the equilibrium constant for the reaction below if a tank was found to contain 1.15 M O2, 0.750 M SO3, and 0.980 M SO2.

        2 SO3(g) <-->2 SO2(g) + O2(g)
A

1.96

43
Q

The position of the equilibrium for a system where K = 4.6 × 10-15 can be described as being favored to ________; the concentration of products is relatively ________.

A

The left; small.

44
Q

The position of the equilibrium for
a system where K = 1.6 × 1014 can be described as being favored to ________; the concentration of products is relatively ________.

A

The right; large.

45
Q

True or False:
When the rate of the forward reaction is twice as fast as rate of the reverse reaction, the system is at equilibrium.

A

False.

46
Q

True or False: When the concentration of the reactants and products does not change, the system is at equilibrium.

A

True.

47
Q

Use Le Chatelier’s principle to predict whether adding CHO2– to the following system at equilibrium will cause the system to move in the direction of the reactants or products.

HCHO2 + H2O ↔ CHO2– + H3O+

A

Equilibrium shifts toward the reactants.

48
Q

Use Le Chatelier’s principle to predict whether removing some HCHO2 in the following system at equilibrium will cause the system to move in the direction of the reactants or products.

HCHO2 + H2O ↔ CHO2– + H3O+

A

Equilibrium shifts towards the reactants.

49
Q

Use Le Chatelier’s principle to predict whether removing some H3O+ in the following system at equilibrium will cause the system to move in the direction of the reactants or products.

HCHO2 + H2O ↔ CHO2– + H3O+

A

Equilibrium shifts towards the products.

50
Q

A given forward reaction is exothermic. Use Le Chatelier’s principle to predict whether adding heat will cause the system to move in the direction of the reactants or products.

A

Equilibrium shifts towards the reactants.

51
Q

A given forward reaction is endothermic. Use Le Chatelier’s principle to predict whether cooling the system will cause the system to move in the direction of the reactants or products.

A

Equilibrium shifts towards the reactants.

PSC: Chemistry (9 decks)

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