Answers26-27 - C - RUSD Chemistry in the Earth SystemThe Energy of Chemical Reactions

Practice Test Answers

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1
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Which energy change takes place when gasoline evaporates from a fuel gas can?

A
Energy remains stationary.
B
Energy becomes transformed.
C
Energy is absorbed.
D
Energy is released.
2
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Which is true about reaction rates?

A
Reaction rates are not dependent on high or low activation energies.
B
Low reaction rates occur only in nonspontaneous reactions.
C
Reaction rates are not related to spontaneity.
D
High reaction rates occur only in spontaneous reactions.
3

Which statement defines the enthalpy of hydration?

A
the change in enthalpy as temperature rises in a liquid
B
the change in enthalpy when gas ions condense to form 1 mol of an ionic solid
C
the change in enthalpy as heat is lost or gained in a reaction
D
the change in enthalpy when 1 mol of a gaseous ion becomes fully hydrated
4

Which statement is usually true about the relationship between activation energy and reaction rates?

A
Low activation energy barriers result in no reaction.
B
High activation energy barriers result in low rates.
C
Low activation energy barriers result in low rates.
D
High activation energy barriers result in no reaction.
5

Which statement best describes the use of catalytic converters in automobiles?

A
They combine the larger hydrocarbon molecules with smaller ones.
B
They increase reaction temperature for cleaner burning.
C
They oxidize hydrocarbons to form less toxic gases.
D
They decrease the rate of the reactions that produce harmful gases.
6

What is the triangle cap h sub sol for KF rightarrow cap k raised to the plus plus cap f raised to the negative power power ? The lattice energy is negative 784 kJ/mol , the enthalpy of hydration for cap k raised to the plus power is negative 336 kJ/mol , and the enthalpy of hydration for cap f raised to the negative power is negative 431 kJ/mol Use triangle cap h sub sol is equal to negative triangle cap h sub lat plus triangle cap h sub hydr

A
1 comma 551 kJ/mol
B
17 kJ/mol
C
negative 17 kJ/mol
D
negative 879 kJ/mol
7

The overall change in enthalpy of a reaction depends only on

A
the path that is taken from the reactants to the products.
B
the reactants and the catalysts only.
C
the reactants and the products.
D
the reactants, the products, and the catalysts.
8

Which statement best describes why rate laws are important?

A
to see if a chemical reaction can actually take place
B
to determine what products are formed in a chemical reaction
C
to determine how fast a chemical reaction will take place
D
to see how much heat energy a chemical reaction releases
9

Propane cap c sub 3 cap h sub 8 g , Δ⁢H_f=−103.8kJ/mol reacts with oxygen to produce carbon dioxide CO sub 2 , Δ⁢H_f=−393.5kJ/mol and water cap h sub 2 cap o , Δ⁢H_f=−241.82kJ/mol according to the equation. cap c sub 3 cap h sub 8 g plus 5 cap o sub 2 g rightarrow 3 CO sub 2 g plus 4 cap h sub 2 cap o g What is the enthalpy of combustion (per mole) of cap c sub 3 cap h sub 8 g ? Use Δ⁢H_rxn=∑(Δ⁢H_f_1p⁢r⁢o⁢d⁢u⁢c⁢t⁢s)−∑(Δ⁢H_f_1r⁢e⁢a⁢c⁢tan⁡t⁢s)

A
2 comma 044 point 0 kJ over mol
B
negative 531 point 5 kJ over mol
C
531 point 5 kJ over mol
D
negative 2 comma 044 point 0 kJ over mol
10

Carbon reacts with oxygen to produce carbon dioxide CO sub 2 times g , Δ⁢H_f=−393.5kJ/mol according to the equation. cap c times s plus 2 cap o sub 2 g rightarrow CO sub 2 times g What is the enthalpy change of the reaction? Use Δ⁢H_rxn=∑(Δ⁢H_f_1p⁢r⁢o⁢d⁢u⁢c⁢t⁢s)−∑(Δ⁢H_f_1r⁢e⁢a⁢c⁢tan⁡t⁢s)

A
negative 196 point 8 kJ
B
negative 393 point 5 kJ
C
393 point 5 kJ
D
196 point 8 kJ
11

Which definition describes activation energy?

A
the speed at which reactants form products in a chemical reaction
B
the diagram showing a change in energy between reactants and products
C
the short-lived, high-energy intermediate between reactants and products
D
the minimum energy that a set of reactants must attain before reaction can occur
12

What advantage does a heterogeneous catalyst provide over a homogeneous catalyst in industrial processes?

A
A heterogeneous catalyst provides an alternate reaction pathway.
B
A heterogeneous catalyst can be easily separated from reactants.
C
A heterogeneous catalyst raises the activation energy higher.
D
A heterogeneous catalyst provides a higher reaction rate.
13

Consider the rate law. cap A plus 3 cap b rightarrow 2 cap c plus 2 cap d The rate increases by a factor of 9 when the concentration of cap A triples.The rate triples when the concentration of cap b triples. What is the new rate law for the reaction?

A
cap r is equal to k cap A cubed cap b cubed
B
cap r is equal to k cap A to the 9th power cap b cubed
C
cap r is equal to k cap A squared cap b
D
cap r is equal to k cap A cubed cap b squared
14

The molar heat of fusion of gold is 12 point 5 5 0 kJ mol inverse At its melting point, how much mass of melted gold must solidify to release 235 point 0 kJ of energy? Use q is equal to n triangle cap h

A
2 comma 949 point 3 g
B
18 point 7 3 g
C
3 comma 688 point 3 g
D
222 point 5 g
15

What is the main reason that it takes 2 to 3 minutes for the reaction to occur between sucrose and sulfuric acid in the dehydration of sucrose?

A
The sulfuric acid has to be consumed before the reaction takes place.
B
The sucrose molecules must rearrange to become the catalyst.
C
The activation energy needs to be overcome in the reaction.
D
The activation energy must be removed from the intermediates.
16

According to Hess’s law, if a series of intermediate reactions are combined, the enthalpy change of the overall reaction is

A
the product of the enthalpy changes of the intermediate reactions.
B
the sum of the enthalpy changes of the intermediate reactions.
C
the difference between the enthalpies of the intermediate reactions.
D
the fraction of the individual enthalpies of the intermediate reactions.

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