OCR Gateway B Chemistry Higher C1, C2, C3 9th June

C1

Which pigment is phosphorescent? (2 marks)

D because it absorbs and stores energy and gives it off as light later, so light makes it become brighter.

Which pigment must be used in baby’s spoons which test for the temperature of the food? (2 marks)

C because it changes to yellow when it is hot which tells you the food is too hot to give to the baby. The heat energy from the food warms up the spoon.

How do oil-based paints dry?

Solvent evaporates and the oil is oxidised by atmospheric oxygen.

Which of these are…? (Can’t remember the questions exactly) (1 mark each)

a) Unsaturated – B b) A c) decolourise bromine water – B d) polymer – C

Don’t remember which words were missing apart from alcohol.

Acid + alcohol --> ester + water

Which two statements explain why water does not remove nail varnish?

1) attraction between the water particles is stronger than the attraction between the water molecules and the nail varnish molecules 2) attraction between the nail varnish molecules is stronger than the attraction between the water molecules and the nail varnish molecules.

Why must perfume be volatile (evaporate easily) and be insoluble in water?

Volatile so perfume particles can reach the nose and be smelled. Insoluble in water so it cannot be washed off easily.

Why is PTFE waterproof and breathable? (2 marks)

PTFE is waterproof and breathable because the pores (holes) are too small for water to pass through but big enough for water vapour to pass through so sweat can leave.

Evaluate the advantages and disadvantages of each fuel. Which is the best fuel? (6 marks)

FUEL A: ADV – highest energy value so is most efficient. Only releases carbon dioxide which contributes to global warming but is not as bad as sulfur dioxide. DISADV – limited availability. Only lasts 20 years (needs to be 25).

FUEL B: ADV – good availability. Lasts for 50 years (long enough for power station). Cheapest. DISADV – releases carbon dioxide and large amounts of sulfur dioxide which causes breathing difficulties for people with asthma.

FUEL C: ADV – good availability. Only releases carbon dioxide which contributes to global warming but is not as bad as sulfur dioxide. DISADV – most expensive. Only lasts 8 years (needs to be 25)

BEST FUEL (own choice) – FUEL B – it is in solid state so can be stored easily at the power station. Cannot leak or escape easily like Fuel A (liquid) and Fuel C (gas).

C2

What is the lithosphere?

It comprises of the crust and upper mantle. It is a cold, rigid layer.

Something about Brass B and wire contact

Don’t know the answer J - I wrote Brass A because it has the best electrical conductivity but I don’t know if its correct.

Balanced symbol equation for making ammonia

N₂ + 3H₂ --> 2NH₃

Can’t remember the acid name and the base name

Something acid + something carbonate à something + water + carbon dioxide

Can’t remember if it was hydroxide or something else

Potassium hydroxide + nitric acid à potassium nitrate (missing word)

In the Haber process, the actual conditions used are: an iron catalyst, 450^OC temperature, and 200 atmospheres pressure. Why are these used? (3 marks)

Iron catalyst increases rate of reaction. Temperature means percentage yield is still high enough to make the sufficient amount needed for that day, and keeps energy cost low. Pressure means percentage yield is still high and keeps plant cost low. It is a compromise.

Electrolysis of copper: Anode: Cu - 2e^- --> Cu²⁺ Cathode: Cu²⁺ + 2e^- --> Cu

Why is this a reduction and oxidation reaction? (1 mark)

Reduction at the cathode because copper ions gain electrons. Oxidation at the anode because copper loses electrons.

All acids have what ions? (1 mark)

H⁺

Evaluate the advantages and disadvantages of using aluminium and steel for the helicopter body. Which is the best metal? (6 marks)

Aluminium does not corrode but steel rusts slowly so aluminium lasts longer than steel. This is because it has an aluminium oxide layer which protects it. Aluminium has a low density so it is lighter and improves fuel economy. Steel is harder (8 compared to 3 of aluminium) so it does not scratch easily. Steel is stronger so it does not break easily. Both these metals are malleable so can be easily bent into shape to make the helicopter body. BEST METAL (own choice) – steel because it is much stronger so if the helicopter crashes, there will be less damage and less harm to the passengers. Its electrical conductivity is not much lower than aluminium (7 compared to 8).

C3

Why is burning fuels an exothermic reaction? (3 marks)

In an exothermic reaction, more energy is released than taken in. When burning fuels, reactant bonds are broken which is endothermic and product bonds are made which is exothermic. It is overall exothermic because more energy is released in bond making than taken in during bond breaking.

6300J of energy is transferred using fuel B. What is the mass of water used in Trevor’s experiment?

6300 = 4.2 x mass x (48-28) Mass = 6300/84 = 75 grams

Someone uses a fuel for a stove. They use fuel A. Is this a sensible choice?

I don’t know the answer J but I wrote – No because although fuel A transfers the most energy, Fuel D has the most energy per gram (energy transferred/ mass of fuel burnt).

Atom economy of reaction 2. Oxygen is a waste product.

Ti + O₂ --> TiO₂

48/ (48 + 32) x 100 = 60%

Percentage yield (not sure of the numbers used so this is a guess) (2 significant figures)

Actual yield/ predicted yield x 100 I think the answer was 82.125 and 82 (2 s.f.)

Why is it important to have a high atom economy and high percentage yield? (2 marks)

High atom economy because there is less production of unwanted waste products, and the process is more sustainable. High percentage yield because there are less reactants wasted which is wasteful and costly.

When does the reaction finish? (For the line with a steeper gradient) (1 mark)

3 minutes

How do the two curves show the rate of reaction is faster for one of the curves (I think one shows the reaction for something with larger surface area and the other for a smaller surface area).

The gradient is steeper for one curve which shows the rate of reaction is faster. The line becomes horizontal earlier which shows the reaction finishes quicker.

Why does the amount of carbon dioxide (product) double when the amount of the hydrochloric acid (limiting reactant – I don’t know what it was called) doubles?

When limiting reactant doubles, there are double more of these particles so there are double more successful collisions. This makes double the product.

Explain how increasing the concentration of the hydrochloric acid and increasing the temperature of the hydrochloric acid increases the rate of reaction. (6 marks)

Increasing concentration means more hydrochloric acid particles are in the same volume so they are more crowded. This makes them collide more often with the magnesium chips. This increases collision frequency as there are more successful collisions, which increase rate of reaction.

Increasing temperature means hydrochloric acid particles have more kinetic energy. This means they move around faster and with more energy and so are more likely to collide with the magnesium chips. This increases collision frequency because there are more frequent, energetic collisions, which increases rate of reaction.

Can’t remember the acid name and the base name

Something acid + something carbonate --> something + water + carbon dioxide
.

Thank you x

There was that q about why scientist study volcanoes and the other one about animal testing n the one about why groups of scientists should publish their work etc

Oh yeah! Do you remember which unit they came up in?

Oh yeah! Do you remember which unit they came up in?

Why does the amount of carbon dioxide (product) double when the amount of the hydrochloric acid (limiting reactant – I don’t know what it was called) doubles?

i wrote that the amount of limiting reactant used is directly proprtional to the amount of product in this case co2. is that right?

i put fuel A instead of B, how many marks would i lose

Also wasn't there another symbol equation and we had to balance it. i think it was C3H80 + oxygen i think