Oxygen, Hydrogen and Testing for Ions and Gases Flashcards
How do you test for sulphates?
- precipitation reaction with barium chloride + dilute HCl(rules out a carbonate)
- white precipitate produced
How can you know that manganese(IV) oxide was used up?
- weigh, filter, dry and weigh again
How do you test for water?
- anhydrous copper(II) sulfate: white powder turns blue in presence of water
- cobalt chloride: blue turns pink in presence of water
How do you used iron or phosphorus to investigate the proportion of oxygen in the atmosphere?
- iron reacts with oxygen in the air to form rust
1. first soak some iron wool in acetic acid (a catalyst). then push the wool into a test tube, put your thumb over the end and invert the tube into a beaker of water
2. over time, the level of water in the test tube will rise
3. iron reacts with oxygen in the air and water rises to fill the space the oxygen took up
4. you need to mark the start and finish of the water
5. calculate percentages
What is CO2 used for?
- carbonated drinks: slightly soluble in water and dissolves in drink under high pressure. produces a slightly acidic solution due to formation of carbonic acid
- fire extinguishers: CO2 more denser than air, so it sinks onto the flames and stops the oxygen from getting to the fire
How do you test for Copper(II), Cu2+?
- precipitation reaction with sodium hydroxide, NaOH
- blue precipitate produced
What are greenhouse gases?
- gases that absorb heat that would normally be radiated out of space, acting as an insulating layer
How do you test for hydrogen?
- makes a squeaky pop with a lighted splint
What colour precipitate do you have when you test for bromide?
- cream precipitate
How do you test for ammonia?
- turns damp red litmus paper blue and pungent smell
What happens when you react carbon with oxygen?
- produces an orange/yellow flame
- produces CO2 gas
- slightly acidic when dissolved in water
How do you test for carbon dioxide?
- turns limewater cloudy
How do you test for carbonates, CO3^2-?
- precipitation reaction with dilute HCl
- white precipitate formed, CaCO3
- lime water turns cloudy because CO2 produced
How do you test for chlorine gas?
- chlorine bleaches damp litmus paper
How do you test for oxygen?
- relights a glowing splint
What colour precipitate do you have when you test for iodide?
- yellow precipitate
How do you produce carbon dioxide with calcium carbonate?
- calcium carbonate (marble chips) is put in the bottom of a flask and dilute hydrochloric acid is added
- dilute HCl reacts with the calcium carbonate to produce calcium chloride, water and carbon dioxide gas
- carbon dioxide gas is collected in a gas syringe or downward delivery
- 2HCl(aq) + CaCO3(s) = CaCl2(aq) + H2O(l) + CO2(g)
What human activities affect the amount of CO2 in the atmosphere?
- deforestation: fewer trees means less CO2 is removed during photosynthesis
- burning fossil fuels: carbon that was locked up is now being released as CO2
What happens when you react sulphur with oxygen?
- pale blue flame
- produces sulfur dioxide
- acidic when dissolved in water
What colour flame does potassium burn with?
- lilac flame
What colour flame does sodium burn with?
- yellow-orange flame
What colour precipitate do you have when you test for chloride?
- white precipitate
How do you test for halides?
- precipitation reaction by adding nitric acid (to rule out carbonate and sulphite) and silver nitrate solution (AgNO3)
Who do you do a flame test to identify metal ions?
- dip a platinum wire loop in HCl to clean it and hold it in a flame
- when it burns without any colour, you can test it
How is carbon dioxide linked to climate change?
- there’s a correlation between increasing levels of CO2 and the gradual heating up of the Earth’s atmosphere
- could cause climate change and sea level rises
How do you test for Iron(III), Fe3+?
- precipitation reaction with NaOH
- brown precipitate formed
What colour flame does calcium burn with?
- brick-red flame
How do you test for metal ions with metal hydroxides?
- many metal hydroxides are insoluble and a precipitate is formed
- add sodium hydroxide solution into the solution
How does thermal decomposition of metal carbonates produce CO2?
- thermal decomposition is when a substance breaks down when heated
- copper(II) carbonate is a green powder that will decompose to form carbon dioxide and copper(II) oxide
- heat copper(II) carbonate then collect gas
- CuCO3(s) = CuO(s) + CO2(g)
How do you test for ammonium, NH4+?
- warm with sodium hydroxide
- test with damp red litmus, so gas can dissolved in it
- pungent ammonia gas produced
- litmus paper turns blue
How do you make oxygen?
- using hydrogen peroxide
- hydrogen will decompose into water and oxygen:
2H2O2(aq) = 2H2O(l) + O2 - manganese(IV) oxide is used as a catalyst
- you can collect over water or gas syringe
- use a tap funnel to control the amount of H2O2 used so that oxygen isn’t lost
What happens when you react magnesium with oxygen?
- magnesium burns with a bright white flame
- white powder formed is magnesium oxide
- slightly alkaline when dissolved in water
How do you test for Iron(II), Fe2+?
- precipitation reaction with sodium hydroxide
- green precipitate produced
What are the proportions of the gases in the atmosphere?
- 78% nitrogen
- 21% oxygen
- almost 1% argon
- 0.04% CO2
How do you used copper to investigate the proportion of oxygen in the atmosphere?
- when heated, copper reacts with oxygen in the air to make copper(II) oxide, so the reaction uses up oxygen
- if you heat an excess of copper in a tube and pass air over it using two syringes, oxygen will be used up
- use 100cm^3 of air
- equation:
2Cu + O2 = 2CuO
What colour flame does lithium burn with?
- crimson-red flame
How do you test if water is pure?
- boil to see if it is 100 degrees
- freezing point 0 degrees
