Answers25-26 KCS18 Chemistry ICHeat

Thermochemical Equations Answers

0 verified answers2 views
1
Free Preview

The enthalpy of formation for C6 H6 (I) is 49.0 kJ/mol. Consider the following reaction.Is the reaction endothermic or exothermic, and what is the enthalpy of reaction? Use .

Question illustration
A
exothermic; Hrxn = 49.0 kJ
Option A
B
exothermic; Hrxn = –49.0 kJ
Option B
C
endothermic; Hrxn = 49.0 kJ
Option C
D
endothermic; Hrxn = –49.0 kJ
Option D
2
Free Preview

Hydrogen reacts with chlorine to form hydrogen chloride (HCl (g), Hf = –92.3 kJ/mol) according to the reaction below.Which statement is correct? Use .

Question illustration
A
The enthalpy of the reaction is –184.6 kJ, and the reaction is exothermic.
B
The enthalpy of the reaction is –184.6 kJ, and the reaction is endothermic.
C
The enthalpy of the reaction is 184.6 kJ, and the reaction is endothermic.
D
The enthalpy of the reaction is 184.6 kJ, and the reaction is exothermic.
3

Which statement is true for most chemical reactions?

A
An energy change occurs during the breaking and forming of bonds.
B
The internal energy of the system increases during a reaction.
C
Energy is released during the formation of reactants.
D
The enthalpy of the products is higher than the enthalpy of the reactants.
4

How is enthalpy used to predict whether a reaction is endothermic or exothermic?

A
When the enthalpy of the reactants is higher than the enthalpy of the products, the reaction is endothermic.
B
When the enthalpy of the products is higher than the enthalpy of the reactants, the reaction is exothermic.
C
When the enthalpy change of the reaction is positive, the reaction is exothermic.
D
When the enthalpy change of the reaction is positive, the reaction is endothermic.
5

Consider the reaction.Standard Enthalpies of FormationSubstanceDHf (kJ/mol)C2 H2 (g)226.73CaCO3 (s)–1206.92CaO (s)–635.09CO (g)–110.525CO2 (g)–393.509H 2 O (I)–285.8H 2 O (g)–241.818C (s), diamond1.895C (s), graphite0.0Based on the equation and the information in the table, what is the enthalpy of the reaction? Use .

Question illustration
A
–453.46 kJ
B
–226.73 kJ
C
226.73 kJ
D
453.46 kJ
6

Which statement about Hf is true?

Question illustration
A
It is positive when the bonds of the product store more energy than those of the reactants.
B
It is zero for any pure substance in its standard state.
C
It is negative when a compound forms from elements in their standard states.
D
It is zero for any compound that is in the liquid state.
7

Which graph represents an exothermic reaction?

A
A graph has Reaction progression on the horizontal axis and energy on the vertical axis. A line starts about halfway up the vertical axis and travels a short distance parallel to the horizontal axis; this segment is A plus B. The line then curves up sharply, peaks, and falls sharply to run parallel to and near the horizontal axis; the final segment is C. A double-headed arrow extends from A plus B to C.
Option A
B
A graph has Reaction progression on the horizontal axis and energy on the vertical axis. A line segment labeled A plus B starts low and runs parallel to the horizontal axis. The line then curves up sharply, peaks, and falls a short distance to run parallel to the horizontal axis; the final segment is labeled C. A double-headed arrow extends from A plus B to C.
Option B
C
A graph has Reaction progression on the horizontal axis and energy on the vertical axis. A line segment labeled A plus B starts halfway up the vertical axis and runs parallel to the horizontal axis for a short distance. The line then peaks and returns to the same level as A plus B and continues parallel to the horizontal axis; this segment is labeled C.
Option C
D
A graph has Reaction progression on the horizontal axis and energy on the vertical axis. A line segment labeled A plus B starts low on the vertical axis and runs parallel to the horizontal axis for a short distance. The line then rises sharply and levels off; this level section is labeled C. A double-headed arrow extends from the level of A plus B to that of C.
Option D
8

Which statement is true if the Hrxn of a reaction is positive?

Question illustration
A
The reaction is endothermic.
B
The reaction is exothermic.
C
There is more reactant than product.
D
There is more product than reactant.
9

Butane C4 H10 (g),(Hf = –125.6), combusts in the presence of oxygen to form CO2 (g) (Hf = –393.5 kJ/mol), and H2 O(g) (Hf = –241.82) in the reaction: What is the enthalpy of combustion, per mole, of butane? Use .

Question illustration
A
–5,315 kJ/mol
B
–2,657.5 kJ/mol
C
2,657.4 kJ/mol
D
5,314.8 kJ/mol
10

The enthalpies of formation of the compounds in the combustion of methane, ,are CH4 (g): Hf = –74.6 kJ/mol; CO2 (g): Hf = –393.5 kJ/mol; and H2 O(g): Hf = –241.82 kJ/mol.How much heat is released by the combustion of 2 mol of methane? Use .

Question illustration
A
80.3 kJ
Option A
B
802.5 kJ
Option B
C
1,605.1 kJ
Option C
D
6,420.3 kJ
Option D

Did you find these answers helpful?

More from this Course

Quiz
10 verified answers

Heat

Quiz
10 verified answers

Heat

Quiz
10 verified answers

Colligative Properties