Key Questions

Question 1

Why do alkaline batteries eventually stop working?

Answer 1

reactant used up and reaction stops

Question 2

what is the reaction profile for an endothermic reaction?

Answer 2

products above reactants

Question 3

what is the reaction profile for an exothermic reaction?

Answer 3

products below reactants

Question 4

making salts rp

Answer 4

1. Measure 20 cm3
   sulfuric acid into a measuring cylinder and pour it into beaker.
2. Heat the acid gently using a Bunsen burner.
3. Add small amounts of insoluble base in this case copper oxide in excess (until no more
   reacts thus no more effervescence is produced).
4. Filter using filter paper and funnel the solution to remove the excess copper oxide.
5. Pour the solution into the evaporating basin.
6. Evaporate the solution using a water bath until crystals start to form.
7. Leave the evaporating basin in a cool place for at least 24 hours.
8. Gently pat the crystals dry between two pieces of filter paper.

Question 5

Advantages and disadvantages of hydrogen fuel cells

Answer 5

Advantages of hydrogen fuel cells
They do not produce any pollution

They produce more energy per kilogram than either petrol or diesel

No power is lost in transmission as there are no moving parts, unlike an internal combustion engine

No batteries to dispose of which is better for the environment

Continuous process and will keep producing energy as long as fuel is supplied

Disadvantages of hydrogen fuel cells
Materials used in producing fuel cells are expensive

High pressure tanks are needed to store the oxygen and hydrogen in sufficient amounts which are dangerous and difficult to handle

Fuel cells are affected by low temperatures, becoming less efficient

Hydrogen is expensive to produce and store

Question 6

Advantages and disadvantages of lithium batteries

Answer 6

These power things that need more energy than an alkaline battery. Once their energy is used, they can simply be recharged.

Lithium batteries are expensive to make and mining the materials needed for them, such as cobalt, causes pollution.

Lithium-ion batteries can also waste a lot of heat energy when they get hot.

Question 7

measuring reactivity of unknown metal

Answer 7

add all of the metals to an acid (1)
measure temperature change or means of comparing rate of reaction
(1)
place the metals in order of temperature change or rate of reaction

Question 8

why use pipettes and burettes?

Answer 8

pipette measures a fixed volume
(accurately)
(but) burette measures variable
volume