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GCSE - Chemistry (New) > Section 2 - Pgs 37-42 > Flashcards

Section 2 - Pgs 37-42 Flashcards

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1
Q

Why is all rain slightly acidic?

A

Carbon dioxide in the air reacts with water to produce a slightly acidic solution.

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2
Q

Carbon dioxide + Water ->

A

Carbon dioxide + Water -> Carbonic Acid

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3
Q

What percentages of what gases make up the atmosphere?

A

Nitrogen - 78%
Oxygen - 21%
Argon - Nearly 1%
Carbon Dioxide - 0.04%

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4
Q

What experiments can be used to investigate the proportions of oxygen in the atmosphere?

A

1) Heating copper in between syringes

2) Using iron to form rust (or phosphorus to form phosphorus oxide)

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5
Q

Describe how copper can be used to calculate the amount of oxygen in the air.

A

1) Set up an excess of copper oxide in the middle of two linked syringes.
2) Make sure the syringes contain 100cm3 of air.
3) Heat the copper until the reaction finishes.
4) The volume of air should reduce to about 80cm3, showing that there is approximately 20cm3 of oxygen in the air (which has reacted with the copper to form copper oxide).

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6
Q

Describe how iron (or phosphorus) can be used to calculate the amount of oxygen in the air.

A

1) Soak some iron wool in acetic acid (a catalyst) and push it into the bottom of a test tube.
2) Put your thumb over the end of the tube, invert it and put it upside down in a beaker of water.
3) Over time, the water level in the test tube will rise. This is because the oxygen in the air is used to make the iron rust and water rises to fill the gap.
4) Mark the start and end positions of the water.
5) Fill the tube up with water to each line and pour this into a measuring cylinder. The difference between the two volumes can be used to work out the percentage of oxygen in air. It should be about 20%.

A similar thing can be done with white phosphorus, which smoulders in air to produce phosphorus oxide.

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7
Q

What is the symbol equation for copper reacting with oxygen?

A

2Cu + O2 -> 2CuO

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8
Q

Describe how oxygen can be prepared in a lab.

A

1) Prepare some hydrogen peroxide (H2O2) and some manganese(IV) oxide catalyst in a conical flask.
2) The hydrogen peroxide decomposes into water and oxygen, which can be collected by:
a. Using a delivery tube to bubble the gas through a delivery tube and into a cylinder or gas jar filled with water.
b. Using a gas syringe.

(Diagram pg 38)

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9
Q

What does hydrogen peroxide decompose into?

A

Water and oxygen

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10
Q

What is the symbol equation for the decomposition of hydrogen peroxide?

A

2H2O2 (aq) -> 2H2O (l) + O2 (g)

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11
Q

What catalyst speeds up the decomposition of hydrogen peroxide?

A

Manganese(IV) oxide

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12
Q

What is formed when an element is burned?

A

An oxide

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13
Q

What does an element react with when it is burnt?

A

Oxygen

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14
Q

Do oxides have an acidic or basic character?

A

They can be either. It depends on the element reacting with oxygen.

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15
Q

Describe the reaction of magnesium burning in air and the products.

A
  • Magnesium burns with a bright white flame

- Magnesium oxide formed, which is a white powder

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16
Q

What is the acidity of magnesium oxide when dissolved in water?

A

Slightly alkaline

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17
Q

What is the symbol equation for burning magnesium in air?

A

2Mg (s) + O2 (g) -> 2MgO (s)

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18
Q

Describe the reaction of carbon burning in air and the products.

A
  • Carbon will burn if very strongly heated
  • It has an orangey/yellowy flame
  • Produces carbon dioxide gas
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19
Q

When will carbon dioxide react with oxygen?

A

When heated very strongly.

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20
Q

What is the acidity of carbon dioxide when dissolved in water?

A

Slightly acidic

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21
Q

What is the symbol equation for burning carbon in air?

A

C (s) + O2 (g) -> CO2 (g)

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22
Q

Describe the reaction of sulphur burning in air and the products.

A
  • Sulphur burns with a pale blue flame

- Produces sulphur dioxide gas

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23
Q

What is the acidity of sulphur dioxide when dissolved in water?

A

Acidic

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24
Q

What is the symbol equation for sulphur burning in air?

A

S (s) + O2 (g) -> SO2 (g)

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25
What are the two ways of producing CO2 in the lab?
1) Dilute acid reacts with calcium carbonate | 2) Thermal decomposition of metal carbonates
26
In gas collection, when is an upwards and when is a downwards delivery used?
Depends on the density of the gas being collected. 1) Delivery tube is fed into a test tube either upwards or downwards. 2) Upwards delivery to collect 'lighter than air' gases (e.g. H2) 3) Downwards delivery to collect 'heavier than air' gases (e.g. CO2)
27
Describe how dilute acid reactions with calcium carbonate can be used to produce carbon dioxide in a lab.
1) Calcium carbonate (marble chips) is put in a flask and dilute hydrochloric acid is added. 2) Dilute HCl reacts with CaCO3 to produce calcium chloride, water and carbon dioxide gas. 3) Carbon dioxide gas is collect in a gas syringe or using downwards delivery. (Diagram Pg 39)
28
What is the word equation for hydrochloric acid reacting with calcium carbonate?
Hydrochloric acid + Calcium carbonate -> Calcium chloride + Water + Carbon dioxide
29
What is the symbol equation for hydrochloric acid reacting with calcium carbonate?
2HCl (aq) + CaCO3 (s) -> CaCl2 (aq) + H2O (l) + CO2 (g)
30
Describe how the thermal decomposition of metal carbonates can be used to produce carbon dioxide in a lab.
1) Heat a metal carbonate (such as copper(II) carbonate) in a test tube. 2) Collect the gas using downward delivery through a delivery tube.
31
What is the word equation for the thermal decomposition of copper(II) carbonate?
Copper carbonate -> Copper oxide + Carbon dioxide
32
What is the symbol equation for the thermal decomposition of copper(II) carbonate?
CuCO3 (s) -> CuO (s) + CO2 (g)
33
What colour changes can be observed when copper(II) carbonate is heated?
The green copper carbonate powder decomposes into black copper oxide and carbon dioxide.
34
What is upward delivery?
When a gas is collected through a delivery tube that points upwards into an inverted test tube.
35
What is downward delivery?
When a gas is collected through a delivery tube that points downwards into an upright test tube.
36
What are some uses of carbon dioxide?
* Carbonated drinks | * Fire extinguishers
37
How does CO2 affect the acidity of a carbonated drink?
It makes it slightly acidic because the water and CO2 form carbonic acid.
38
What is the symbol equation for carbon dioxide reacting with water?
CO2(g) + H2O(l) -> H2CO3(aq)
39
Why is CO2 used in fire extinguishers?
It is more dense than air, so it sinks onto the flames and stops the oxygen getting to the fire.
40
When are CO2 extinguishers used?
When a water extinguisher isn't safe (e.g. when putting out an electrical fire).
41
Is CO2 a greenhouse gas?
Yes
42
What are some human reasons for increased amounts of CO2 in the atmosphere?
* Deforestation | * Burning fossil fuels
43
What is the effect of increased CO2 concentration?
It causes global warming, which can in turn result in other types of climate change, such as severe flooding due to melting ice caps.
44
What is global warming?
The gradual heating up of the Earth's atmosphere due to increasing levels of greenhouse gases.
45
What are the tests for cations?
* Some burn with a distinctly coloured flame * Some form a coloured precipitate with NaOH * Ammonium compounds give off ammonia with NaOH
46
What cations can be tested for by looking at their flames?
* Lithium - Crimson red * Sodium - Yellow-orange * Potassium - Lilac * Calcium - Brick red * Barium - Green
47
How can you tell if a metal is lithium?
* Burn it | * Gives crimson red flame
48
How can you tell if a metal is sodium?
* Burn it | * Gives yellow-orange flame
49
How can you tell if a metal is potassium?
* Burn it | * Gives lilac flame
50
How can you tell if a metal is calcium?
* Burn it | * Gives brick red flame
51
How can you tell if a metal is barium?
* Burn it | * Gives a green flame
52
Describe the process of testing a cation by looking at its flame colour.
* Clean a platinum loop by dipping it in some dilute HCl * Hold this in a flame * Do this until the loop burns without any colour * Now you can dip the loop in the cation and test for it
53
Describe why the precipitate tests for cations work.
* Many metal hydroxides are insoluble so they precipitate out of solution * They have distinct colours which allows them to be identified
54
Which cations can be tested for by adding NaOH?
* Calcium - White precipitate * Copper(II) - Blue precipitate * Iron(II) - Sludgy green precipitate * Iron(III) - Reddish brown precipitate * Aluminium - White at first, but then redissolves to form colourless solution * Magnesium - White precipitate * Ammonium (NH4+) - Gives off ammonia gas, which smells
55
How can you test for copper(II) (Cu2+) ions in a compound?
* Add NaOH to a solution of the mystery compound | * Blue precipitate forms
56
How can you test for magnesium ions in a compound?
* Add NaOH to solution of mystery compound | * White precipitate forms
57
How can you test for iron(II) (Fe2+) ions in a compound?
* Add NaOH to a solution of the mystery compound | * Sludgy green precipitate forms
58
How can you test for iron(III) (Fe3+) ions in a compound?
* Add NaOH to a solution of the mystery compound | * Reddish brown precipitate forms
59
How can you test for aluminium ions in a compound?
* Add NaOH to solution of mystery compound | * White precipitate forms, but then redissolves in excess NaOH
60
How can you test for ammonium ions (NH4+) in a compound?
* Add NaOH to a solution of the mystery compound | * Ammonia is produced -> Has a strong smell + turns damp red litmus paper blue
61
How can you test for calcium ions in a compound?
* Add NaOH to solution of mystery compound | * White precipitate forms
62
What are the tests for anions?
* Adding HCl * Adding HCl and then barium chloride * Nitric acid and then silver nitrate
63
What anions can be tested for by adding hydrochloric acid?
Carbonates (CO3 2-)
64
What anions can be tested for by adding hydrochloric acid and then barium chloride?
Sulphate (SO4 2-)
65
What anions can be tested for by adding nitric acid and then silver nitrate?
Halides: Cl- - White precipitate Br- - Cream precipitate I- - Yellow precipitate
66
How can you test for carbonate (CO3 2-) ions in a compound?
* Add HCl | * CO2 is given off -> Can test for this using limewater
67
How can you test for sulphate (SO4 2-) ions in a compound?
* Add HCl -> To get rid of any carbonate or sulfite ions, which would also produce a precipitate * Add barium chloride * White precipitate is produced
68
How can you test for chloride (Cl-) ions in a compound?
* Add nitric acid -> To get rid of any carbonate or sulphate ions, which would also produce a precipitate * Add silver nitrate * White precipitate is produced
69
How can you test for bromide (Br-) ions in a compound?
* Add nitric acid -> To get rid of any carbonate or sulphate ions, which would also produce a precipitate * Add silver nitrate * Cream precipitate is produced
70
How can you test for iodide (I-) ions in a compound?
* Add nitric acid -> To get rid of any carbonate or sulphate ions, which would also produce a precipitate * Add silver nitrate * Yellow precipitate is produced
71
Why is hydrochloric acid added before testing for sulphates and nitric acid before testing for halides?
It gets rid of any carbonate or sulfite ions before the test (which would affect the results by producing a precipitate).
72
Give the half equation for the test for copper ions.
Cu2+ + 2OH- -> Cu(OH)2
73
Give the half equation for the test for iron(II) ions.
Fe2+ + 2OH- -> Fe(OH)2
74
Give the half equation for the test for iron(III) ions.
Fe3+ + 3OH- -> Fe(OH)3
75
Give the half equation for the test for carbonate ions.
CO3 2- + 2H+ -> CO2 + H2O
76
Give the half equation for the test for sulphate ions.
Ba2+ + SO4 2+ -> BaSO4
77
Give the half equation for the test for chloride ions.
Ag+ + Cl- -> AgCl
78
Give the half equation for the test for bromide ions.
Ag+ + Br- -> AgBr
79
Give the half equation for the test for iodide ions.
Ag+ + I- -> AgI

GCSE - Chemistry (New) (18 decks)

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