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Question 1

What is the difference between heat and temperature?

Answer 1

Heat is the total energy transferred due to temperature difference; temperature measures the average kinetic energy of particles.

Question 2

How is energy transferred in chemical reactions?

Answer 2

As heat, through bond breaking and forming.

Question 3

What is an exothermic reaction?

Answer 3

A reaction that releases energy to the surroundings (ΔH < 0).

Question 4

What is an endothermic reaction?

Answer 4

A reaction that absorbs energy from the surroundings (ΔH > 0).

Question 5

What happens to temperature in an exothermic reaction?

Answer 5

It increases.

Question 6

What happens to temperature in an endothermic reaction?

Answer 6

It decreases.

Question 7

How does the energy profile of an exothermic reaction look?

Answer 7

Reactants are higher than products; ΔH is negative.

Question 8

How does the energy profile of an endothermic reaction look?

Answer 8

Products are higher than reactants; ΔH is positive.

Question 9

What does the peak in an energy profile represent?

Answer 9

The activation energy.

Question 10

What does ΔH⦵ represent?

Answer 10

Standard enthalpy change under standard conditions (298 K, 1 atm, 1 mol).

Question 11

How is enthalpy change calculated using q = mcΔT?

Answer 11

q = mass × specific heat capacity × temperature change.

Question 12

How to find enthalpy per mole from q?

Answer 12

ΔH = q / mol, usually converted to kJ/mol.

Question 13

What happens when bonds are broken?

Answer 13

Energy is absorbed (endothermic).

Question 14

What happens when bonds are formed?

Answer 14

Energy is released (exothermic).

Question 15

How is ΔH calculated using bond enthalpies?

Answer 15

ΔH = Σ(bonds broken) - Σ(bonds formed).

Question 16

What are average bond enthalpies?

Answer 16

Mean values from many molecules; used for estimating ΔH.

Question 17

What is Hess’s Law?

Answer 17

The total enthalpy change is the same regardless of the reaction path.

Question 18

How is Hess’s Law applied?

Answer 18

Use known enthalpies to construct an enthalpy cycle and solve for unknown ΔH.

Question 19

What is the general equation for hydrocarbon combustion?

Answer 19

CxHy + O2 → CO2 + H2O.

Question 20

What happens in incomplete combustion?

Answer 20

Produces CO or C (soot) instead of CO2.

Question 21

What are the products of alcohol combustion?

Answer 21

CO2 and H2O (complete); CO or C and H2O (incomplete).

Question 22

What are fossil fuels?

Answer 22

Coal, crude oil, and natural gas.

Question 23

Why are fossil fuels a concern?

Answer 23

They release CO2, contributing to the greenhouse effect.

Question 24

What is the greenhouse effect?

Answer 24

Trapping of heat in Earth’s atmosphere due to greenhouse gases like CO2 and CH4.

Question 25

What are biofuels?

Answer 25

Fuels made from biological material (e.g., ethanol from fermentation).

Question 26

Are biofuels renewable or non-renewable?

Answer 26

Renewable.

Question 27

What are advantages of biofuels?

Answer 27

Lower net CO2 emissions, renewable.

Question 28

What are disadvantages of biofuels?

Answer 28

Compete with food production, require land and energy to produce.

Question 29

What is a fuel cell?

Answer 29

A device that converts chemical energy into electricity using fuels like H2 or CH3OH.

Question 30

What is the anode half-equation in a hydrogen fuel cell?

Answer 30

H2 → 2H+ + 2e–

Question 31

What is the cathode half-equation in a hydrogen fuel cell?

Answer 31

O2 + 4H+ + 4e– → 2H2O

Question 32

What is the overall equation in a hydrogen fuel cell?

Answer 32

2H2 + O2 → 2H2O

Question 33

What is the anode half-equation in a methanol fuel cell?

Answer 33

CH3OH + H2O → CO2 + 6H+ + 6e–

Question 34

What is the cathode half-equation in a methanol fuel cell?

Answer 34

3/2 O2 + 6H+ + 6e– → 3H2O