Section 4-Inorganic Chemistry P1 (pg35-40, pg51-53) Flashcards
What is produced when group 1 elements react with oxygen?
What are some examples?
- form metal oxides (this is why metals tarnish when left in the air- a dull metal oxide layer has formed)
- Lithium->lithium oxide(Li₂O)
- Sodium->sodium oxide(Na₂O) and sodium peroxide(Na₂O₂)
- Potassium->potassium peroxide(K₂O₂) and potassium superoxide(KO₂)
What is produced in the reaction between group 1 elements and water?
- they all react vigorously
- the reaction produces a metal hydroxide and the solution is alkaline(hence they are called the alkali metals)
- the reaction also produces hydrogen (hence the fizzing)
What happens to the reactivity of Group 1 as you move down the group?
- Group 1 elements become more reactive as you go down the group
- This is visible with their reactions with water: lithium takes the longest to react where as potassium takes the smallest amount of time, this trend is also visible with their reactions with oxygen
What is the general trend as you go down the halogens?
- the elements have a darker colour
- have a higher boiling point
- reactivity decreases
What are the properties of Chlorine (Cl₂)?
- green gas
- boiling point -34°C
What are the properties of Bromine (Br₂)?
- red-brown liquid
- boiling point 59°C
What are the properties of Iodine (I₂)?
- dark grey solid
- boiling point 185°C
What reactions go on with the halogens?
Displacement reactions- more reactive halogens will displace less reactive ones
What happens when Potassium chloride (colourless solution) is added to:
1) Chlorine water(colourless)
2) Bromine water(orange)
3) Iodine water(brown)
1) no reaction
2) no reaction
3) no reaction
What happens when Potassium bromide (colourless solution) is added to:
1) Chlorine water(colourless)
2) Bromine water(orange)
3) Iodine water(brown)
1) orange solution formed(because the bromine has been displaced by the chlorine)
2) no reaction
3) no reaction
What happens when Potassium iodide (colourless solution) is added to:
1) Chlorine water(colourless)
2) Bromine water(orange)
3) Iodine water(brown)
1) brown solution formed(because the iodine has been displaced by the chlorine)
2) brown solution formed(because the iodine has been displaced by the bromine)
3) no reaction
What do halogen displacement reactions involve?
Halogen displacement reactions involve the transfer of electrons. REDOX REACTIONS(oxidation and reduction happen simultaneously)
Define Oxidation:
Loss of electrons
Define Reduction:
Gain of electrons
What is OIL RIG?
O - oxidation
I - is
L - loss
R - reduction
I - is
G - gain
What main gases are in the atmosphere and what is the percentage composition?
Nitrogen - 78%
Oxygen - 21%
Argon - nearly 1%
Carbon Dioxide - 0.04%
What different ways can you test the amount of oxygen in the air?
- IRON reacting with the air(will form rust)
- PHOSPHORUS reacting with the air(phosphorus will react with oxygen in the air to make phosphorus oxide)
- COPPER reacting with the air(will react to form copper oxide)
- FLOATING CANDLE(the candle will burn and use the oxygen in the air)
Describe how iron wool (metal) can be used to work out how much oxygen there is in the air:
- soak some iron wool in acetic acid(acid will catalyse the reaction), push the wool into a measuring cylinder, invert the measuring cylinder into a beaker of water
- record the starting position of the beaker water level in the measuring cylinder
- over time the water level in the measuring cylinder will rise(because the iron reacts with the oxygen and the water rises to fill the space the oxygen took up)
- leave until the water level stops changing and then record the finishing position of the water in the measuring cylinder
- then find the change in volume and divide it by the starting volume and times by 100
Describe how phosphorus can be used to determine the percentage of oxygen in the air:
- place the phosphorus in a tube and attach a glass syringe at either end with 100cm³ air in one syringe and the other empty
- heat the phosphorus and use the syringes to pass the air over the phosphorus(forming phosphorus oxide)
- keep on sending air across it until the volume doesn’t change then do 100 - your starting volume to find out the percentage of oxygen in the air
When you burn something what does it react with?
When you burn something it reacts with OXYGEN in the air
-this forms an oxide (it can be acidic or basic)
What happens when you burn magnesium?
- burns with a bright white flame
- white power is formed(magnesium oxide)
- magnesium oxide is slightly alkaline when dissolved in water
What happens when you burn hydrogen?
- burns very easily with oxygen(can be explosive)
- has an orangey/yellow
- water is produced
- often used as a test for hydrogen gas
What happens when you burn sulfur?
- pale blue flame
- produces sulphur dioxide
- sulphur dioxide dissolved in water is acidic
Describe the thermal decomposition of a carbonate to produce carbon dioxide and how you can collect the carbon dioxide:
- heat metal carbonate -> carbon dioxide + metal oxide
- thermal decomposition breaks down a substance into simpler substances
- copper(II) carbonate(green solid) that will easily decompose to form carbon dioxide and copper(II) oxide(black solid)
- collect the carbon dioxide using a bung delivery tube and a separate test tube
What is the temperature of the earth determined by?
The balance between the heat the earth gets from the sun and the heat it radiates back out to space
What are examples of greenhouse gases and what do they naturally do?
Carbon dioxide, methane, water vapour
-they act naturally as an insulating layer, they absorb most of the heat that would be normally be radiated back into space and re-radiate it towards the earth
What are two examples of human activity which affects the amount of carbon dioxide in the atmosphere?
- deforestation (so less carbon dioxide is removed from the atmosphere by photosynthesis)
- burning fossil fuels (carbon that was trapped in these fuels are being released as carbon dioxide)
How is increasing amounts of carbon dioxide in the air linked to climate change?
-there is a correlation between the increasing levels of carbon dioxide and global warming, although the earth’s temperature varies naturally the rate of increase in temperature is unnatural
What are the effects of global warming?
Global warming is a type of climate change
- it can cause:
- > changing rainfall patterns
- > severe flooding due to the polar ice caps melting and sea levels rising
Describe how you carry out a flame test:
- clean a platinum wire loop by dipping it in dilute HCl and then holding it in a flame
- repeat until the wire burns without any colour, then dip the wire into your test sample and then put it into a non-luminous, non-roaring flame and look for the colour
What charge have cations got?
positive
What charge have anions got?
negative
What test and result shows that lithium is present in a substance?
flame test
red flame
What test and result shows that sodium is present in a substance?
flame test
yellow flame
What test and result shows that potassium is present in a substance?
flame test
lilac flame
What test and result shows that calcium is present in a substance?
flame test
orange-red flame
What test and result shows that copper(II) is present in a substance?
flame test
blue-green flame
reacted with NaOH, coloured precipitate formed
blue precipitate
Describe how you carry out a test to form a coloured precipitate with NaOH:
- many hydroxides are insoluble so form precipitates when formed, some have characteristic colours
- add a few drops of sodium hydroxide solution to your test solution
- if you get a coloured precipitate formed then you can work out what cation is present
What test and result shows that iron(II) is present in a substance?
reacted with NaOH, coloured precipitate formed
sludgy green precipitate
What test and result shows that iron(III)is present in a substance?
reacted with NaOH, coloured precipitate formed
reddish brown precipitate
Describe how you can carry out a test to see whether there is an ammonium compound present:
- add your test substance to some sodium hydroxide
- if ammonia gas has been produced you can find out buy placing a damp piece of red litmus paper and if ammonia is present then it will turn blue
Describe how you can test for carbonates:
- add HCl to your test sample
- if carbonates are present then carbon dioxide will be released
- test gas produced with lime water to see whether carbon dioxide has been produced
Describe how you test for sulphates:
- add HCl to your test substance and then barium chloride
- a white precipitate of barium sulphate means the original compound contain sulphate
Why is hydrochloric acid added in the test for sulphates?
- to get rid of any traces of carbonate or sulphite ions before you do the test
- otherwise them two anions could compromise your test
Describe how you test for the presence of the halide ions:
-add nitric acid to your test substance and then add silver nitrate solution
What test and result shows that chloride ions are present in a substance?
add nitric acid and silver nitrate
white precipitate
What test and result shows that bromine ions are present in a substance?
add nitric acid and silver nitrate
cream precipitate
What test and result shows that iodide ions are present in a substance?
add nitric acid and silver nitrate
yellow precipitate
Why is nitric acid added in the test for the halide ions?
- to get rid of the carbonate or sulphate ions before the test
- can’t use hydrochloric acid this time because chlorine is what you are testing for and it is already present in hydrochloric acid
Describe the test for chlorine:
Damp blue litmus paper
if chlorine is present: litmus paper will turn red then will be bleached white
Describe the test for Oxygen:
Glowing splint
if oxygen is present: the splint will relight
Describe the test for Carbon Dioxide:
Bubble the gas through limewater
if carbon dioxide is present: limewater will go cloudy
Describe the test for Hydrogen:
lit splint
if hydrogen is present: hear a squeaky pop
Describe a test for Ammonia:
damp red litmus paper
if ammonia is present: litmus paper will turn blue
What is a chemical test for the presence of water?
copper(II) sulphate crystals
- wet it is blue, dry it is white
- you can heat wet copper(II) sulphate to make it anhydrous
- so you can use it to test for the presence of water
What is a physical test for the purity of water?
- test for either the boiling or freezing point
- only pure water will boil at 100°C and freeze at 0°C
