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Chemistry Overview > CHEMISTRY EXAM > Flashcards

CHEMISTRY EXAM Flashcards

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1
Q

2 differences between physical properties of elements in group 1 and those of transition metals

A

Transition are stronger, harder and denser

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2
Q

How metals conduct electricity

A

Their delocalised electrons carry electrical charge through the metal

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3
Q

Plan a method to investigate the effect of changing the mass of sodium carbonate powder on the highest temperature reached

A

Measure equal volumes of hydrochloric acid in polystryene cup

Add different masses of sodium carbonate to separate trials

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4
Q

how can a reaction profile show the reaction is exothermic

A

Overall change is negative

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5
Q

How the student should obtain crystals of zinc chloride from a solution of zinc chloride.

A

Warm mixture and stir

Continue to add zinc oxide to beaker until all of dilute hydrochloric acid has reacted

Remove excess zinc oxide

Obtain crystals of zinc chloride from solution

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6
Q

Zn + CuCl2 → ZnCl2 + Cu

A

+2 +2
Zn + Cu → Zn + Cu

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7
Q

why rubidium is more reactive than potassium.

A

larger atomic size

lower ionization energy

Greater tendency to lose electrons and form positive ions in chemical reactions

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8
Q

Equation for the reaction of rubidium with water

A

2Rb + 2H2O ——–> 2RbOH + H2

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9
Q

Calculate relative atomic mass of neon

A

20.179

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10
Q

Correct half equation for production of sodium

A

+ -
2Na + 2e —–> 2Na

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11
Q

Why products of electrolysis must be kept apart

A

To prevent them from reacting with each other and interfering with the desired chemical processes

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12
Q

Which type of particle passes through the mesh in the electrolysis of molten sodium chloride

A

Ions pass through the mesh

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13
Q

Which two ions are present in aqueous sodium chloride solution in addition to sodium ions and chloride ions

A

Sodium Na+

Chloride ions Cl-

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14
Q

Aqueous sodium chloride solution is electrolysed in a different industrial process.
Two gases and an alkaline solution are produced

Name the alkaline solution produced

A

Sodium hydroxide

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15
Q

Explain how the alkaline solution has produced sodium hydroxide

A

Reduction at the cathode

Oxidation at the Anode

The released electrons flow through the external circuit back to the cathode, where they participate in the reduction of water molecules

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16
Q

Why aluminum is more expensive than carbon

A

Aluminium is more reactive than carbon so it must be extracted from its compounds using electrolysis

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17
Q

Why the products are difficult to separate if magnesium is used to reduce silicon dioxide

A

They are both solids

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18
Q

Why pH of acid depends on concentration of acid

A

Higher concentrations produce a greater number of hydrogen ions, resulting in a lower pH value

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19
Q

Why does the pH of an acid depend on the strength of the acid

A

Strong acids dissociate completely and produce a high concentration of H+ ions, resulting in a lower pH

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20
Q

25.00 cm’ of the hydrochloric acid reacted with 23.50 cm’ of the 0.100 mol/dm3 barium hydroxide solution.
The equation for the reaction is:
2HClaq) + Ba(OH)2(aq) → BaCl(aq) + 2H2O(I)
Calculate the concentration of the hydrochloric acid in mol/dm?.

A

3
0.188 mol/dm

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21
Q

Explain why the electrical conductivity of the mixture was zero when the sulfuric acid had just been neutralised

A

All hydrogen and hydroxide ions are consumed in neutralization reaction to form water

No free ions left in the solution to conduct electricity

Ekectrical conductivity becomes 0 as there are no ions available to carry the electric current

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22
Q

The student then added a further 10 cm’ of barium hydroxide solution
The electrical conductivity of the mixture increased
Why?

A

Due to the increase in the concentration of hydroxide ions in the solution, which can conduct electricity

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23
Q

Element Q is a dull solid with a melting point of 44 °C.
Element Q does not conduct electricity.
Which section of the periodic table in Figure 1 is most likely to contain element Q?

A

D

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24
Q

Element R forms ions of formula R2* and R3+
Which section of the periodic table in Figure 1 is most likely to contain element R?

A

B

Transition metals

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25
Q

Suggest why poly(butene) insulation must be removed from scrap copper wire before the copper is recycled.

A

If insulation not removed, can burn or produce harmful gases when exposed to high temperatures,

This affects quality of recycled copper and damaging the recycling equipment.

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26
Q

How scrap copper wire can be recycled to make new copper water pipes.

A

Melting down the scrap copper wire

Refining the molten copper

Forming it into pipes.

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27
Q

Suggest two reasons why recycling scrap copper is more sustainable than extracting copper from copper ores.

A

No need for landfills

Cheaper than mining and extracting new copper

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28
Q

Which solution can be added to copper sulfate solution to show the presence of copper(Il) ions

A

Sodium hydroxide solution can be added

Formation of a pale blue precipitate of copper(II) hydroxide

29
Q

Describe one test to show the presence of sulfate ions in copper sulfate solution.
Give the result of the test

Test

Result

A

Add a small amount of barium chloride solution to the copper sulfate solution

A white precipitate of barium sulfate forms if sulfate ions are present in the copper sulfate solution

30
Q

Determine the mass of the empty test tube

A

25.6g - 2.0g = 23.6g

31
Q

Explain why the mass of the test tube and contents decreased

Hydrated cobalt chloride

A

The mass of the sample decreases because the water molecules are lost as gas

32
Q

Suggest why the test tube and contents were heated until the mass did not change.

A

To ensure all water was removed from hydrated cobalt chloride

33
Q

When 238 g of hydrated cobalt chloride is heated until the mass does not change, 88.1 kJ of energy is taken in.
The student heated 2.00 g of hydrated cobalt chloride until the mass did not change.

Calculate the energy taken in during this reaction.

A

(88.1 x 2.00) ➗ 238

176.2 ➗ 238

0.739kJ

34
Q

What type of reaction takes place when hydrated cobalt chloride is heated?

A

Dehydration reaction

35
Q

Evaluate the use of glass for milk bottles compared with the use of a polymer for milk bottles

A

Raw material extraction - glass requires high energy, polymers require moderate energy

Manufacturing process - glass - high energy consumption, polymer - moderate energy consumption

Transportation - glass heavier than polymer leads to high tranportation costs

Glass high durability, polymer moderate durability

Glass fully recyclable, Recyclable, but with limitations due to potential degradation of material quality

Glass - does not release harmful chemicals during incineration, polymer may release harmful chemicals during incineration

36
Q

Milk is also sold in cardboard cartons.

A carton is made using 40 cm’ of cardboard.

The density of the cardboard is 0.40 g/cm?.

Calculate the mass of the carton

A

Mass = density x volume

0.40 x 40 = 16g

37
Q

The two useful materials produced from feedstock for the petrochemical industry are

A

Detergents

Solvents

38
Q

Balanced symbol equation for complete combustion of C9H20

A

C9H20 + 14O2 —————> 9CO2 + 10H2O

39
Q

Why sulfur impurities are removed before the petrol is burned in car engines

A

Sulfur impurities are removed from petrol before it’s burned in car engines because sulfur can lead to air pollution, health problems, and engine damage

40
Q

Viscosity

A

A measure of the resistance of a substance to flow

41
Q

A student predicted that heavy fuel oil is more viscous than kerosene

The student’s prediction was correct

Justify the student’s prediction

A

In table 4 the heavy fuel oil fraction has a wider range of carbon atoms in each molecule compared to kerosene

This shows heavy fuel oil molecules are larger and more complex than kerosene molecules

They are likely to have strong intermolecular forces hplding them together as a result heavy fuel oil will have higher viscosity compared to kerosene

42
Q

Conditions for cracking

A

High temperature 450-750 C

High pressure around 1-70atm

Prescence of catalyst for catalytic cracking

43
Q

Which pair of hydrocarbon molecules turn bromine water colourless

A

C7H16

C8H18

44
Q

Describe how sewage is treated to remove organic matter

A

Screening to remove large objects (sticks, leaves plastic’

Sewage enters a primary settling tank

The partially treated sewage is then transferred to a biological treatment tank

Tertiary treatment may be used

Sludge collected undergoes further treatment to reduce its volume

Treated sewage may undergo disinfection to kill harmful pathogens

45
Q

The pair of concentrations that could represent X in Table 5 after the desalination process for sea water is

A

Na + : 0.5mol/dm3

Cl- : 0.003mol/dm3

46
Q

Explain why the concentrations of sodium ions and of chloride ions in the ground water in Table 5 are unchanged by Process 1

A

Because ground water is not desalinated during process 1

47
Q

Explain why the ground water in Table 5 requires Process 2 before the water is safe to drink

A

To ensure ground water is safe for human to drink by removing or reducing contaminants, pathogens and impurities

48
Q

Suggest what the company means by ‘pure’.

A

The water meets certain quality standards or criteria for purity suitable for its intended use

49
Q

Describe the test for chlorine gas

A

Collect a sample of chlorine gas

Bubble gas through solution of potassium iodide in water

Observe the color change in the solution

50
Q

Result of chlorine gas

A

If chlorine gas present, it reacts with potassium iodide solution to produce iodine

51
Q

Explain the change in the percentage of gas in the region labelled A on Figure 3

A

Reflects transition from an atmosphere dominated by carbon dioxide to one with increasing levels of oxygen

52
Q

Explain the change in the percentage of gas in the region labelled B on Figure 3

A

Reflects long-term removal of carbon dioxide from atmosphere

53
Q

Explain the change in the percentage of gas in the region labelled C on Figure 3

A

Reflects long-term increase in oxygen levels in Earth’s atmosphere

54
Q

What process caused the changes in the percentages of gases in the region labelled C on Figure 3

A

Photosynthesis

55
Q

Natural gas is a fossil fuel

Describe how deposits of natural gas were formed

A

Millions years ago organic matter accumulated on the ocean floor

Layers of sediment accumulated over organic matter

Subjected to high temperature and high pressure

56
Q

Give the sources of the nitrogen and of the hydrogen used in the Haber process

A

Nitrogen - air

Hydrogen - natural gas

57
Q

How does the equation for the reaction show that the atom economy of the forward reaction is 100%?

A

There is only 1 product

58
Q

Explain how the ammonia produced is separated from the unreacted nitrogen and hydrogen in X

A

Mixture is cooled so only ammonia liquefies

59
Q

Determine the percentage yield of ammonia at 450 °C and 500 atmospheres

A

500

60
Q

Explain why these conditions are chosen for economical production of ammonia in the Haber process

A

Higher temperature gives higher rate and shifts position of equilibrium to the left

Use of catalyst gives higher rate because activation energy lowered

High pressure shifts position of equilibrium to the right

Use of catalyst has no effect on position of equilibrium

61
Q

Sulfur produced in reaction

Why does mixture become cloudy

A

Sulfur is insoluble

62
Q

Exothermic reaction

A

When energy is transferred to the surroundings, this is called an exothermic

63
Q

The percentage of light reaching the light sensor decreases by 1% when 7.1 × 10-5 moles of sulfur is produced
Determine the rate of reaction in mol/s for the production of sulfur at 30 seconds.

A

-3
2.13 x 10 moles/s

64
Q

Why rate of reaction changes between 0 and 60 seconds

A

Rate decreases because concentration of reactants decreases

Greatest rate at start

Greatest concentration of reactants at start

65
Q

The line of best fit on Figure 8 is horizontal between 80 and 120 seconds because the reaction stopped.
Why did the reaction stop?

A

Hydrochloric acid all used up

66
Q

How could the student improve the method so that the same percentages of light reached the light sensor

A

Stop light from other sources reaching light sensor

67
Q

Name given to similar results obtained on different days under the same conditions by same student

A

Repeatable

68
Q

Which expression represents the relationship between the volume (V) of sodium thiosulfate solution used and the mass (m) of sulfur produced?

A

V O( m

Weird shape

69
Q

Determine the simplest whole number ratio of the volumes of
sodium thiosulfate solution : hydrochloric acid

A

Volume of NaS2O3 solution
______________________________
Volume of hydrochloric acid

= 0.25

1:4

Chemistry Overview (7 decks)

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