C4.2
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How do you test for CO2
You test for CO2 using limewater. Limewater is calcium hydroxide solution Ca(OH)2. The calcium hydroxide reacts with carbon dioxide to form water an a white precipitate of calcium carbonate causing the limewater to become cloudy, when the carbon dioxide is bubbled through it.
Formula of reaction of limewater and carbon dioxide
CO2 (g) + Ca(OH)2 (aq) -> H20 (l) + CaCO3 (s)
What is the test for chlorine
Chlorine dissolves in water to form an acidic solution. It also bleaches dyes - changes them from coloured to colourless. 1. Use a drop of tap water to dampen blue litmus paper 2. Hold the paper near the source of chlorine 3. If chlorine is present it turns red then white
Formula for reaction of chlorine and water
Cl2 (g) + H2O (l) -> HCl (aq) + HClO
How to smell a substance in a laboratory
To smell a substance you should hold it well away from your nose then you should breathe in just enough air to almost fill your lungs. Then you should hold it away from your nose and waft any smell towards you. Take a cautious swig.
What is the test for hydrogen
Place a lit split near the mouth of the container of gas. If hydrogen is present should ignite with a squeaky pop.
What is the test for oxygen
Place glowing splint near mouth of container gas. If O2 is present the splint should relight.
What happens when metal ions are heated
When metal ions are heated energy is transferred to their electrons. This makes their electrons move to higher energy shells. When they move back to their normal electron shells, energy is transferred to the surroundings as radiation which you see as light.
What colour is the flame test for lithium
Red
What colour is the flame test for sodium
Yellow
What colour is the flame test for potassium
Lilac
What colour is the flame test for calcium
Orange-red
What colour is the flame test for copper
Green-blue
What are group 1 metal hydroxides soluble in
They are soluble in water but most other metal hydroxides are insoluble.
What do you use in experiments for the hydroxide test
You use sodium hydroxide solution in experiments.
What do different metals produce when reacting with sodium hydroxide
They form different coloured precipitates
What is the colour of the iron(II) precipitate
Green
What is the colour of the iron(III) precipitate
Orange-brown
What is the colour of the copper(II) precipitate
Blue
What is the colour of the calcium(2+) precipitate
white
What is the colour of the zinc(II) precipitate
white
What is the different between calcium hydroxide and zinc hydroxide
Zinc hydroxide dissolves to form a colourless solution but calcium hydroxide doesn’t dissolve.
What is another test for metal hydroxides
Take the metal and add a few drops of sodium hydroxide
What are the steps for flame test
Niochrome loop is cleansed by putting it into HCl and then you should put it in the flame to cleanse it. The you should did the loop into the metals and put it in a flame and see the colour.