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IGCSE CHEMISTRY > Unit 1 - Hydrogen, Oxygen & The Atmosphere > Flashcards

Unit 1 - Hydrogen, Oxygen & The Atmosphere Flashcards

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1
Q

Metal + water –>

A

Metal + water –> metal hydroxide + hydrogen

This only works for metals soluble in water (Potassium, Sodium, Calcium)
Eg. Na + H2O –> NaOH + 1/2 H2

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2
Q

Simple test for hydrogen gas

A

Put lit splint into gas.

If test is positive, a pooping sound will me made.

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3
Q

Physical test to show if water is pure

A

Boil water. If water boils at exactly 100 degrees then it is pure. Impure water takes longer to boil

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4
Q

Test for oxygen

A

Put glowing splint in gas.

If test is positive, splint will relight

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5
Q

Metal + acid –>

A

Metal + acid –> salt + hydrogen

This only works if the metal is more reactive than hydrogen and of the salt is soluble

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6
Q

What do all acids contain

A

Hydrogen

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7
Q

How do you identify a salt ?

A

Salts can be easily identified, since they usually consist of positive ions from a metal with negative ions from a non metal

Eg sodium chloride, zinc sulfate etc

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8
Q

Metal + steam –>

A

metal + steam –> metal oxide + hydrogen

Eg zinc + steam –> zinc oxide + hydrogen

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9
Q

What gases can be found in air ?

A 
Nitrogen 78%
Oxygen 21%
Argon 0.96%
Carbon dioxide 0.03%
Neon 0.0006%
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10
Q

Hydrochloric acid

A

HCl

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11
Q

Sulphuric acid

A

H2SO4

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12
Q

Hydrochloride acid + magnesium –>

A

Magnesium chloride + hydrogen

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13
Q

Sulphuric acid + magnesium –>

A

Magnesium sulphate + hydrogen

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14
Q

Hydrochloric acid + aluminium –>

A

Aluminium chloride + hydrogen

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15
Q

Sulphuric acid + zinc –>

A

Zinc sulphate + hydrogen

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16
Q

Describe the combustion of hydrogen

A

The combustion of hydrogen is its reaction with oxygen. Water is created as well as lots of energy

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17
Q

Describe the chemical test for water

A

Add anhydrous copper(II) sulphate (white powder).

If water if present, the white powder will change to a blue colour

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18
Q

Describe the laboratory preparation of oxygen from hydrogen peroxide

A

When dilute hydrogen peroxide (H2O2) is decomposed, either by heating it or by the use of a catalyst such as manganese(IV) oxide (MnO2), oxygen is evolved and water is left behind

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19
Q

Equation to show the decomposition of hydrogen peroxide

A

Hydrogen peroxide –> water + oxygen

2H2O2 (aq) –> 2H2O (l) + O2 (g)

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20
Q

Describe a soluble basic (alkaline) oxide

A

These oxides dissolve in water to form hydroxides. They react with acids to form salts but do not react with other alkalis. Group 1 and some group 2 oxides are of this type

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21
Q

Describe insoluble basic oxides

A

The oxides do not dissolve in water. They react with acids to form salts but do not react with alkalis. Some group 2 oxides and transition metal oxides are of this type.

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22
Q

Describe amphoteric oxides

A

These oxides do not dissolve in water. They react with acids to form salts and react with alkalis to form salts with strange names. Metals near to the metal/non-metal border in the periodic table are of this type (eg zinc or aluminium)

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23
Q

Describe acidic oxides

A

These oxides usually dissolve in water to form acids. They react with alkalis to form salts but do not react with other acids. Non-metal oxides are usually of this type.

24
Q

When do salts form

A

Salts form when a metal replaces the hydrogen in an acid

25
Q

Magnesium + oxygen –>

A

2Mg (s) + O2 (g) –> 2MgO (s)

Magnesium (silver solid) burns with a white clams to form magnesium oxide (white powder).

26
Q

Magnesium oxide + water –>

A

2MgO (s) + H2O (l) –> Mg(OH)2 (aq,s)

Magnesium hydroxide is PH10 (weak alkaline)

27
Q

Carbon + oxygen –>

A

C (s) + O2 (g) –> CO2 (g)

Carbon (black solid) burns fairly steadily with a yellow flame to form Carbon dioxide (colourless gas), or sometimes Carbon monoxide (CO)

28
Q

Carbon dioxide + water –>

A

CO2 (g) + H2O (l) –> H2CO3 (aq)

Carbonic acid formed in PH5 (weak acid)

*carbon monoxide does not dissolve in water

29
Q

Sulfur + oxygen –>

A

S (s) + O2 (g) –> SO2 (g)
or
S8 (s) + 8O2 (g) –> 8SO2 (g)

Sulfur (yellow solid) burns quite steadily with a blue flame to form Sulfur dioxide (colourless gas)

30
Q

Sulphur dioxide + water –>

A

SO2 (g) + H2O (l) –> H2SO3 (aq)

Sulfur dioxide dissolves in water to form sulfuric acid.
PH1, strong acid

31
Q

Describe neutral oxides

A

These oxides usually don’t dissolve in water. They do not react with alkalis or acids. Non-metal oxides are usually of this type. If a non-metal forms two oxides the one with more oxygen will be more acidic and the one with less oxygen more neutral

32
Q

Describe how to determine the percentage of oxygen by volume using white phosphorus (large bell jar - method 1)

A

Put a large bell jar containing a known volume of air into a dish with water (outside and inside), inside the jar have white phosphorous.
Phosphorous reacts with oxygen in the air. This produces heat which forces air to expand at first. The phosphorus oxide formed is a solid which dissolves in water, so the water replaces the equal volume of oxygen (about 1/5 of air), therefor oxygen is roughly 20% of the air.
(See booklet on composition of air)

33
Q

Describe a more exact version of method 1 to find percentage of oxygen in air (graduated tube - method 2)

A

A volume of air is put in a graduated tube (you can see the markings 1,2,3….) is put into water. The white phosphorus (moist iron wool or filing can also be used) are put on top of copper wire and put into the air. The phosphorous reacts with the oxygen and the water replaces the equal volume of oxygen in the air.

(See booklet on composition of air)

34
Q

White phosphorous + oxygen –>

A

P4 (s) + 5O2 (g) –> 2P2O5 (s)

35
Q

Describe the most accurate method of determining the percentage of oxygen in air (syringes - method 3)

A

The apparatus is a tube of hard glass, connected to two gas syringes (A and B). The tube is packed with small pieces of pink copper wire. One syringe contains 100cm³ of air, the other is empty. The tube is heated by a Bunsen Burner. The air is pushed through the heated copper into the other syringe, the oxygen reacts with the wire which starts to turn black. The air in passed over the heated copper several times (to react all the oxygen). After about 3 minutes, the apparatus is allowed to cool me all left over air is pushed into one syringe and the volume is measured. This continues until the volume of air no longer decreases, showing that all the oxygen has been used up. The final volume is taken

36
Q

What is a pollutant

A

A pollutant is a potentially harmful chemical formed either naturally or as a waste product of a chemical or industrial process and dispersed into the environment

37
Q

What are the main air pollutants

A

Sulfur dioxide, smoke, nitrogen oxides, Carbon monoxide and hydrocarbons

38
Q

How does sulfur dioxide form

A

SO2 is produced by burning coal which contains 2% sulfur impurities.

S + O2 –> SO2

39
Q

What happens when sulfur dioxide dissolves in water

A

When sulfur dioxide is released it dissolves in rainwater giving sulfurous acid (sulfuric (IV) acid).
SO2 + H2O –> H2SO3

This cm be oxidised by the oxygen in the air to five sulfuric acid (sulfuric (VI) acid) or acid rain.
H2SO3 + 1/2 O2 –> H2SO4

40
Q

Name some problems caused by acid rain

A

Sulfur dioxide in the atmosphere affects people with asthma

Attacks structures made of iron
Fe + H2SO4 –> FeSO4 + H2

damages marble or limestone (calcium carbonate)
CaCO3 + H2SO4 –> CaSO4 + CO2

Nitric oxides cause leaching of potassium and calcium nutrients and poisonous aluminium and lead salts

41
Q

How are nitrogen oxides formed

A

In car engines, the temperature reached is high enough to allow nitrogen and oxygen to react, forming various nitrogen oxides.

In lightning storms nitrogen and oxygen in the air combine to for, nitrogen(II) oxide (nitric oxide).
N2 (g) + O2 (g) -spark-> 2NO (g)

Nitrogen(II) oxide reacts with oxygen to form nitrogen dioxide
NO + 1/2 O2 –> NO2

Nitrogen dioxide dissolves in water to give a mixture of nitric(III) acid and nitric(IV) acid.
H2O + 2NO2 –> HNO2 + HNO3

42
Q

What weak acid does normal rain contain

A

Rain naturally contains carbonic acid. This is very weak and is not harmful. Rain is classified as acid rain if the water contains acid stronger than carbonic acid.

43
Q

What two materials could be used to produce hydrogen in a safe way ?

A

Zinc + hydrochloric acid –> zinc chloride + hydrogen

44
Q

Which catalyst can be used to break down hydrogen peroxide

A

Manganese (IV) oxide

45
Q

What were the gases in the original atmosphere

A

Carbon dioxide, water vapour, hydrogen, nitrogen

46
Q

Where did the oxygen in the atmosphere originally came from

A

First green plants (photosynthesis)

47
Q

ph7 (green)

A

Neutral

48
Q

ph 1-3 (red)

A

Strong acid

49
Q

ph 4-6 (Orange / yellow)

A

Weak acid

50
Q

ph 8-10 (light blue/green)

A

Weak alkali

51
Q

ph 11-14 (blue / black)

A

Strong alkali

52
Q

Solubility of carbonates in water

A

All carbonates are insoluble

Except ammonium carbonate, sodium carbonate and potassium carbonate

53
Q

Solubility of chlorides in water

A

All chlorides are soluble

Except lead chloride, silver chloride

54
Q

Solubility of nitrates in water

A

All nitrates are soluble in water

NO EXCEPTIONS

55
Q

Solubility of sulfates in water

A

Sulfates are soluble in water

Except barium sulfate, lead sulfate,

IGCSE CHEMISTRY (16 decks)

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