Quiz about Bond Enthalpies

Question 1

Does breaking bonds require energy, release energy, or not involve energy at all?

Accepted Answer

requires energy to break

Answer

releases energy when broken

Answer

No energy involved

Question 2

Which statement is FALSE for an endothermic reaction?

Accepted Answer

Products have stronger bonds than reactants

Answer

Products higher in energy and less stable

Answer

Reactants lower in energy and more stable

Answer

Reactants have stronger bonds than products

Question 3

Bond making and bond breaking. Which of following is TRUE?

Accepted Answer

During bond breaking, heat is absorbed

Answer

During bond making, heat is absorbed

Answer

During bond breaking, heat is released

Answer

None of the above

Question 4

Using the reaction & table above, determine the change in energy and whether or not the reaction is endothermic or exothermic:

Accepted Answer

-2045 kJ exothermic

Answer

-2054 kJ endothermic

Answer

2045 kJ endothermic

Answer

2045 kJ exothermic

Question 5

Which of the following statements is true about bond enthalpy?

Accepted Answer

Bond enthalpy is the energy required to break one mole of bonds in gaseous molecules.

Answer

Bond enthalpy is the energy released when one mole of bonds is formed in gaseous molecules.

Answer

Bond enthalpy is the energy required to form one mole of bonds in liquid molecules.

Answer

Bond enthalpy is the energy released when one mole of bonds is broken in liquid molecules.

Question 6

What is the bond enthalpy of a C-H bond if breaking it requires 413 kJ/mol?

Accepted Answer

413 kJ/mol

Answer

-413 kJ/mol

Answer

0 kJ/mol

Answer

826 kJ/mol

Question 7

In a chemical reaction, if the total bond enthalpies of the reactants are greater than the products, what can be inferred?

Accepted Answer

The reaction is exothermic.

Answer

The reaction is endothermic.

Answer

The reaction is at equilibrium.

Answer

The reaction does not occur.

Question 8

How does bond enthalpy relate to bond strength?

Accepted Answer

Higher bond enthalpy indicates stronger bonds.

Answer

Higher bond enthalpy indicates weaker bonds.

Answer

Bond enthalpy does not relate to bond strength.

Answer

Bond enthalpy is inversely proportional to bond strength.

Question 9

Calculate the enthalpy change for the reaction: @@ ext{H}_2(g) + ext{Cl}_2(g) ightarrow 2 ext{HCl}(g) $$ given bond enthalpies: $$ ext{H-H} = 436 ext{ kJ/mol} $$, $$ ext{Cl-Cl} = 242 ext{ kJ/mol} $$, $$ ext{H-Cl} = 431 ext{ kJ/mol}@@.

Accepted Answer

-184 kJ/mol

Answer

-92 kJ/mol

Answer

92 kJ/mol

Answer

184 kJ/mol

Question 10

What is the bond enthalpy of an O=O bond if it requires 498 kJ/mol to break?

Accepted Answer

498 kJ/mol

Answer

-498 kJ/mol

Answer

0 kJ/mol

Answer

996 kJ/mol

Question 11

In the context of bond enthalpies, what does a negative enthalpy change indicate?

Accepted Answer

The reaction is exothermic.

Answer

The reaction is endothermic.

Answer

The reaction is at equilibrium.

Answer

The reaction does not occur.

Question 12

Which of the following bonds would you expect to have the lowest bond enthalpy?

Accepted Answer

I-I

Answer

F-F

Answer

Cl-Cl

Answer

Br-Br

Question 13

How is bond enthalpy related to the stability of a molecule?

Accepted Answer

Higher bond enthalpy generally means more stable molecules.

Answer

Higher bond enthalpy generally means less stable molecules.

Answer

Bond enthalpy does not affect molecular stability.

Answer

Bond enthalpy is inversely related to molecular stability.

Question 14

What is the significance of bond enthalpy in predicting reaction spontaneity?

Accepted Answer

It helps determine if a reaction is exothermic or endothermic.

Answer

It directly predicts reaction spontaneity.

Answer

It has no significance in reaction spontaneity.

Answer

It is inversely related to reaction spontaneity.

Question 15

Which of the following is true about average bond enthalpies?

Accepted Answer

They are calculated from the enthalpies of bonds in different molecules.

Answer

They are specific to a single molecule.

Answer

They are always exact values.

Answer

They are not useful in thermodynamic calculations.

Question 16

Why is the bond enthalpy of a triple bond generally higher than that of a double bond?

Accepted Answer

Triple bonds have more shared electrons, increasing bond strength.

Answer

Triple bonds have fewer shared electrons, decreasing bond strength.

Answer

Triple bonds are longer, making them stronger.

Answer

Triple bonds are shorter, making them weaker.

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