EXAM - To learn

Question 1

Describe the effect/role of a catalyst

Answer 1

A catalyst provides an alternative energy pathway with lower total activation energy.
Thus greater proportion of particles have sufficient energy to react.
Thus more successful collisions per unit time.
Faster rate of reaction/

Question 2

Describe three precautions that should be taken to ensure that the standard solution prepared is of the correct concentration.

Answer 2

No Bubbles 
Bottom of meniscus on calibration line 
Mix Throughly
Hold vertically when judging volume
View from side when judging
Rinse vessel holding solid, transfer rinsing to flask.

Question 3

Describe how hydrogen bonding occurs

Answer 3

Hydrogen atom attached to highly electronegative atom (e.g. O, N or F).
Attracted to lone pair of electrons on adjacent O, N, F.

Question 4

State one change that would need to be made to the set up of the atomic spectrometer (when changing metal)

Answer 4

Change Lamp
Change wavelength of lamp
Change frequency of lamp

Question 5

State one change that would need to be made to the calibration of the atomic spectrometer (when changing metal)

Answer 5

Use standard solutions of new metal to make new calibration curve.

Question 6

Describe how carbon dioxide helps to maintain a steady temperature in the Earth’s atmosphere.

Answer 6

Radiation from sun is re-reradiated as infra-red from the earth’s surface.
CO2 absorbs heat/infrared
the rate at which heat is lost by the atmosphere is equal to the rate at which it is trapped.
Thus a steady temperature is maintained.

Question 7

State one reason why permanent suspension of clay in water may lead to the death of aquatic plants.

Answer 7

No light can reach plants

TF, no photosynthesis.

Question 8

Explain why carbon dioxide produced in aerobic and anaerobic decomposition of glucose does not enhance the greenhouse effect.

Answer 8

When glucose is made CO2 is removed from air
When the glucose releases this CO2 from a renewable source it is just replace this CO2
Therefore, no extra CO2 put into the air.

Question 9

State one reason why the use of an aluminium-air battery may be considered as a desirable alternative to the combustion of fossil fuels to power motor vehicles.

Answer 9

no greenhouse gases produced 
no NOx or SO2 
no products of incomplete combustion
no contribution to acid rain
quiet
fossil fuels are non-renewable and in limited supply

Question 10

Explain why the aluminium-air battery cannot be considered a fuel cells

Answer 10

One reactant is not continuously supplied and will run out

One electrode is consumed and so cell will stop operating

Question 11

For a calorimetry set up, suggest one improvement that could be made and state how this would help to increase the accuracy of the result

Answer 11

Metal calorimeter would absorb more heat
Heat shield would reduce heat loss
Stirrer would distribute heat evenly
remove air from calorimeter so it does not absorb heat
put candle closer to improve heat transfer

Question 12

State two factors that held constant through an experiment attempting to determine the enthalpy of a type of wax.

Answer 12

Same balance for weighing
same thermometer
same temperature around the system
same calorimeter
same measuring cylinder

Question 13

Explain why the arrangement of the atoms around Nitrogen is a trigonal pyramid

Answer 13

lone pair of electrons + three covalent bonds
Thus, 4 regions of electron pairs
regions repel each other and spread out evenly so maximum distance between each pair.
Lone pair of electrons result in trigonal pyramid for other atoms.

Question 14

State one advantage to the consumer of using fuel cells rather than other galvanic cells to produce energy.

Answer 14

Does not need replacing

Question 15

explain why unpolluted rainwater is acidic

Answer 15

CO2 is an acidic oxide

Dissolves in/ reacts with water to form acidic solution

Question 16

What are the conditions to produce a ester?

Answer 16

Heat
Aqueous
Reflux
Alkaline / hydroxide environment 
High pH

Question 17

State one advantage of using natural rubber over synthetic rubber

Answer 17

Reduces CO2 emissions
Reduces use of non-renewable resources
Uses renewable resources
Biodegradable

Question 18

State one advantage of using synthetic rubber over natural rubber

Answer 18

Properties and compositions can be modified for a variety of purposes
Increased variety of structures to suit different purposes
Natural habitat preserved
No need for rubber plantations

Question 19

Explain why starch is a carbohydrate

Answer 19

Starch is derived from monomers which are poly-hydroxy aldehydes

Question 20

Discuss one advantage of making a polymer from starch as a raw material compared to fossil fuels

Answer 20

Starch is obtained from plants which are renewable and can be produced in relatively short time scales, unlike fossil fuels which are non-renewable and can only be produced in extended geological timescale.

Question 21

Explain why the retention times of … and … differ

Answer 21

(molecule with longer retention time) exhibited stronger interactions with the stationary phase compared to (other molecule). This resulted in a longer retention time for (molecule with longer retention time) as it travelled at a slower rate through the column compared to (other molecule).

Question 22

Describe how disulfide links make materials elastic

Answer 22

As forces are applied, the protein chains move past one another to the limits of the crosslinks connecting them. When the forces are removed the cross-links return th chains to their original positions resulting in elastic materials.

Question 23

In regions where soils contain a high concentration of sodium ions it is referred to as sodic. Mud-bricks constructed from clay soils that are sodic are prone to cracking.
Explain why.

Answer 23

in these soils sodium ions exchange with magnesium and calcium ions on the surface of clay sheets. The small highly positive (+2) Mg and Ca ions flocculate the clay layers binding them together to maintain the structure. Replacement with less positive charged sodium ions weakens the interactions between the clay layer weakening the structure.

Question 24

Suggest one advantage of the production of waste heat from a fuel cell.

Answer 24

Waste heat can be used to warm homes and businesses in winter or colder climates.

Question 25

State one advantage of electricity production from a fuel cell compared to steam turbines.

Answer 25

fuel cells are more efficient than steam turbines

Question 26

State one advantage of a flow cell compared to a solid oxide fuel cell.

Answer 26

[ONE OF]

• flow cells are not limited in their size and output for
  their desired application
• Do not need to be heated to operating temperatures
  before use

Question 27

What is the charge of zinc cation?

Answer 27

2+

Question 28

How can an acid be identified in an equation?

Answer 28

It donates a H+

e.g. could ionise and donate H+ to form H3O+

Question 29

Explain why the exothermic nature of the polymerisation reaction is beneficial to the manufacturer.

Answer 29

Heat released can be use to:

• heat reactants
• generate electricity