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A Level Chemistry OCR B > Elements from the Sea > Flashcards

Elements from the Sea Flashcards

1
Q

State the appearance and state of Chlorine at room temperature.

Halogens

A

Pale yellow/ green gas.

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2
Q

State the appearance and state of Bromine at room temperature.

Halogens

A

Brown/ orange/ red liquid.

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3
Q

State the appearance and state of Iodine at room temperature.

Halogens

A

Dark grey solid.

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4
Q

What do oxidation states show?

Oxidation states

A

An atom’s oxidation state tells us how many electrons it has donated or accepted to form an ion or a bond.

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5
Q

Why does an ionic substance need to be molten or in solution before you can electrolyse it?

Electrolysis

A

An electric current can only pass through an ionic substance when its ions are free to move about.

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6
Q

Describe how you would set up the equipment for the electrolysis of a solution of aqueous copper sulfate.

Electrolysis

A
  • Connect each electrode to the power supply.
  • Place the electrodes into a beaker containing a solution of aqueous copper sulfate, making sure that the electrodes aren’t touching each other.
  • Turn the power supply on.
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7
Q

What is formed at the anode when a concentrated halide solution is electrolysed?

Electrolysis

A

The halogen will be formed at the anode.

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8
Q

Two carbon electrodes are placed into molten copper chloride and the power supply is turned on.
What would you see happening at the anode? Explain your answer.
[2 marks]

Electrolysis

A

At the anode, you would see bubbles of gas appearing because chloride ions are losing electrons to form chlorine.

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9
Q

Two carbon electrodes are placed into molten copper chloride and the power supply is turned on.
What would you see happening at the cathode? Explain your answer.
[2 marks]

Electrolysis

A

At the cathode, you would see the electrode being plated because copper ions are gaining electrons to form copper metal.

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10
Q

What is brine?

Electrolysis

A
  • a solution of water with high concentrations of salts - mainly sodium chloride, but also some bromine and iodine salts
  • occurs naturally in salt lakes and seawater, and can be made by dissolving rock salt in water
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11
Q

Describe what occurs at the cathode.

Electrolysis

A

positive cations more to the negative electrode, the cathode, and gain electrons. REDUCTION

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12
Q

Describe what occurs at the anode.

Electrolysis

A

negative anions move to the positive electrode, the anode, and lose electrons.
OXIDATION

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13
Q

How do you calculate percentage atom economy?

A

molecular mass of desired product / sum of molecular mass of all reactants
x100

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14
Q

What does REDOX stand for?

Redox reactions

A

Reduction is Gain of electrons.
Oxidation is Loss of electrons.

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15
Q

What happens to the oxidation state of a substance when it’s reduced?

Redox reactions

A

The oxidation state will decrease.

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16
Q

During a redox reaction, an oxidising agent _____ electrons and is _____.

Redox reactions

A

During a redox reaction, an oxidising agent gains electrons and is reduced.

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17
Q

What is a reducing agent?

Redox reactions

A

A substance that is oxidised. It donates electrons.

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18
Q

What happens to the oxidation state of a substance when it’s oxidised?

Redox reactions

A

The oxidation state will increase.

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19
Q

During a redox reaction, a reducing agent ____ electrons and is ______.

Redox reactions

A

During a redox reaction, an oxidising agent loses electrons and is oxidised.

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20
Q

What is an oxidising agent?

Redox reactions

A

A substance that is reduced. It accepts electrons.

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21
Q

Use oxidation states to balance this redox reaction:
Ca(s) + Al³⁺(aq) → Ca²⁺(aq) + Al(s)
[1 mark]

Redox reactions

A

3Ca(s) + 2Al³⁺(aq) → 3Ca²⁺(aq) + 2Al(s)

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22
Q

What colour solution is formed when iodine dissolves in cyclohexane?

Halogens

A

purple

23
Q

What colour solution is formed when bromine dissolves in cyclohexane?

Halogens

A

Red/ brown

24
Q

What colour solution is formed when chlorine dissolves in cyclohexane?

Halogens

A

Pale green

25
Q

What colour is Fluorine gas/ vapour?

Halogens

A

Colourless gas.

26
Q

What colour is Chlorine gas/ vapour?

Halogens

A

Pale yellow/ green gas

27
Q

What colour is Bromine gas/ vapour?

Halogens

A

brown/ orange/ red gas

28
Q

What colour is Iodine gas/ vapour?

Halogens

A

Purple gas

29
Q

What colour is Astatine gas/ vapour?

Halogens

A

Dark purple gas.

30
Q

What colour solution is formed when chlorine dissolves in water?

Halogens

A

Pale yellow/ green solution.

31
Q

What colour solution is formed when bromine dissolves in water?

Halogens

A

Brown/ orange/ red solution.

32
Q

What colour solution is formed when iodine dissolves in water?

Halogens

A

Brown solution

33
Q

How are hydrogen halides made?

Hydrogen Halides

A

Hydrogen halides can be made by adding a concentrated acid to a solid, ionic halide.

34
Q

What type of reactions can reach a dynamic equilibrium?

Equilibrium

A

Reversible reactions.

35
Q

Kc is dependent on what?

Equilibrium

A

Temperature.

36
Q

what is volatility?

A

a measure of how easy it is to vaporise something (turn something from a liquid to a gas)

37
Q

What specific risks does chlorine pose to humans?

Halogens

A

Toxic:

  • Irritation of eyes, skin, respiratory system
  • Reacts with water in mucus, in lungs, to form HCl, causing drowning
38
Q

Chlorine is transported in pressurised tanks which are usually lined with steel. Why is it essential that the interior of a tank is dry?

Halogens

A

Chlorine reacts with water to produce corrosive acids.

39
Q

What are the 2 main uses of chlorine?

Halogens

A
  • Sterilising water by killing bacteria
  • Making bleach
40
Q

Explain the difference between a co-product and by-product.

A
  • Co-product: from intended reaction. Useful
  • By-product: from side reactions. Not useful
41
Q

What is the strongest oxidising agent in group 7?

Halogens

A

Fluorine

42
Q

State and explain the trend in thermal stability of the hydrogen halides, down the group.

Hydrogen Halides

A

Thermal stability decreases down group
- Bond enthalpies decrease because:
- Halide ion becomes larger
- Outermost bonding electrons become further from nucleus
- Weaker electrostatic attraction

43
Q

What is the oxidation state of uncombined elements or elements made of the same atom? e.g. H₂

Oxidation states

A

Oxidation state = 0

44
Q

Rule for oxidation state of a simple/ monatomic ion. e.g Na+ and Mg2+

Oxidation states

A

The oxidation state is the same as its charge. So oxidation state of Mg2+ is +2.

45
Q

Rule for oxidation state of a complex ion. e.g. SO4 2-

Oxidation states

A

The overall oxidation state is the same as the overall charge of the ion. e.g. the oxidation states of the individual atoms will add up to the overall oxidation state.

46
Q

Rule for oxidation state of a neutral compound.

Oxidation states

A

Overall oxidation state = 0

47
Q

State the oxidation state of hydrogen, H and give the exception.

Oxidation states

A

+1
except in metal hydrides where it is -1.

48
Q

State the oxidation state of hydrogen, H₂

Oxidation states

A

0

49
Q

State the oxidation state of oxygen and give the exceptions.

Oxidation states

A

Usually -2.

Exceptions:
Peroxides = -1
OF₂ = +2
O₂F₂ = +1

50
Q

State the oxidation state of group 1 elements.

Oxidation states

A

Always +1

51
Q

State the oxidation state of group 2 elements.

Oxidation states

A

Always +2

52
Q

State the oxidation state of Aluminium, Al.

Oxidation states

A

Always +3

53
Q

State the oxidation state of fluorine.

Oxidation states

A

Always -1

54
Q

State the oxidation state of chlorine.

Oxidation states

A

-1

Except if in a compound with F and O - it will have a positive value.

A Level Chemistry OCR B (12 decks)

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