Reactivity 1

Question 1

What happens to the energy in an exothermic reaction?

Answer 1

Excess energy is given out to the surroundings as heat

Question 2

What happens to the energy in an endothermic reaction?

Answer 2

Excess energy required is taken in from the surroundings

Question 3

Do exothermic reactions have a positive or negative ∆H value?

Answer 3

Negative

Question 4

Do endothermic reactions have a positive or negative ∆H value?

Answer 4

Positive

Question 5

What is ΔH⦵ measured in?

Answer 5

kJ mol^-1

Question 6

What is ΔH⦵?

Answer 6

Standard enthalpy change

Question 7

Is energy required to form a chemical bond?

Answer 7

No

Question 8

Is energy required to break a chemical bond?

Answer 8

Yes

Question 9

What is the formula to calculate enthalpy changes?

Answer 9

ΔH⦵ = ΔH⦵(bonds broken) - ΔH⦵(bonds formed)

Question 10

If you are doing a simultaneous equation and you rearrange the formula, what happens to ΔH?

Answer 10

Reverse the sign

Question 11

Arrange from strongest to weakest: single covalent bond, double covalent bond, triple covalent bond

Answer 11

Triple covalent, double covalent, single covalent

Question 12

What is the idea with the Hess’ Law problems for the indirect determination of an enthalpy change? (triangles)

Answer 12

A going directly to C or through B

Question 13

How do you find the bond enthalpy in the indirect determination of an enthalpy change?

Answer 13

Figure out the number of bonds broken, and divide previous answer by said number

Question 14

Specific energy of a fuel formula

Answer 14

energy released from the fuel/mass of fuel consumed

Question 15

Units for specific energy of a fuel

Answer 15

kJ kg^-1

Question 16

If you know the enthalpy of combustion, how do you find the specific energy?

Answer 16

Dividing by the molar mass

Question 17

Three main fossil fuels

Answer 17

Coal, crude oil, natural gas

Question 18

How is oil and natural gas produced?

Answer 18

Anaerobic decomposition of marine organisms

Question 19

How is coal produced?

Answer 19

Terrestrial vegetation

Question 20

Advantages of natural gas

Answer 20

Clean, easily transported, higher specific energy than coal or oil

Question 21

Disadvantages of natural gas

Answer 21

Contributes to global warming, limited lifespan, uneven distribution

Question 22

Advantages of oil

Answer 22

Easily transported, feedstock for organic chemicals, convenient fuel for vehicles

Question 23

Disadvantages of oil

Answer 23

Contributes to global warming, limited lifespan, risk of marine pollution (oil spills)

Question 24

Advantages of coal

Answer 24

Present in large quantities, feedstock for organic chemicals, releases more energy than renewable sources, longer lifespan

Question 25

Disadvantages of coal

Answer 25

Contributes to global warming, not as easily transported, mining coal is dangerous, dirty

Question 26

What is the greenhouse effect?

Answer 26

Greenhouse gases absorbing some of the infrared heat from the earth and re-radiating it back into the earth.

Question 27

What is a carbon footprint?

Answer 27

Total amount of greenhouse gases produced during human activities

Question 28

What energy is converted in photosynthesis?

Answer 28

Light energy to chemical energy

Question 29

What is the photosynthesis equation?

Answer 29

6CO2 + 6H20 → C6H12O6

Question 30

What is biomass?

Answer 30

Organic material that can be used as an energy source

Question 31

How is liquid fuel obtained from biomass?

Answer 31

Fermentation

Question 32

What is the equation for obtaining liquid fuel from biomass?

Answer 32

C6H12O6 → 2C2H5OH + 2CO2

Question 33

What is gasohol composed of?

Answer 33

10% ethanol and 90% gasoline

Question 34

What is a common use for gasohol?

Answer 34

Used in unmodified cars, making them less reliant on crude oil.

Question 35

Advantages of biomass

Answer 35

Renewable and always available, doesn’t significantly contribute to the greenhouse effect, safer to produce, reduces landfill amount

Question 36

Disadvantages of biomass

Answer 36

Uses up land that could be used for animals, increases the use of fertilisers which could pollute water, removes nutrients from the soil, methods of conversion are small scale.

Question 37

In what form is the energy given out during the combustion of hydrogen in oxygen to form water?

Answer 37

Electricity (not heat)

Question 38

Do hydrogen fuel cells need an external source of electricity?

Answer 38

No

Question 39

What is the product of hydrogen fuel cells?

Answer 39

Water

Question 40

What are the electrolytes used in alkaline fuel cells?

Answer 40

NaOH or KOH

Question 41

What is used as the electrolyte in an acidic fuel cell?

Answer 41

An acid

Question 42

What is the overall reaction equation in alkaline and acidic fuel cells?

Answer 42

2H2 + O2 → 2H2O

Question 43

What are the products of a methanol fuel cell?

Answer 43

Carbon dioxide and water

Question 44

If a reaction is reversed, what happens to the ΔH value?

Answer 44

It switches (positive/negative, negative/positive)/changes the sign