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OCR gcse ChEMisTry > C4.2 > Flashcards

C4.2 Flashcards

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1
Q

How do you test for CO2

A

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.

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2
Q

Formula of reaction of limewater and carbon dioxide

A

CO2 (g) + Ca(OH)2 (aq) -> H20 (l) + CaCO3 (s)

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3
Q

What is the test for chlorine

A

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

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4
Q

Formula for reaction of chlorine and water

A

Cl2 (g) + H2O (l) -> HCl (aq) + HClO

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5
Q

How to smell a substance in a laboratory

A

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.

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6
Q

What is the test for hydrogen

A

Place a lit split near the mouth of the container of gas. If hydrogen is present should ignite with a squeaky pop.

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7
Q

What is the test for oxygen

A

Place glowing splint near mouth of container gas. If O2 is present the splint should relight.

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8
Q

What happens when metal ions are heated

A

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.

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9
Q

What colour is the flame test for lithium

A

Red

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10
Q

What colour is the flame test for sodium

A

Yellow

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11
Q

What colour is the flame test for potassium

A

Lilac

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12
Q

What colour is the flame test for calcium

A

Orange-red

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13
Q

What colour is the flame test for copper

A

Green-blue

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14
Q

What are group 1 metal hydroxides soluble in

A

They are soluble in water but most other metal hydroxides are insoluble.

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15
Q

What do you use in experiments for the hydroxide test

A

You use sodium hydroxide solution in experiments.

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16
Q

What do different metals produce when reacting with sodium hydroxide

A

They form different coloured precipitates

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17
Q

What is the colour of the iron(II) precipitate

A

Green

18
Q

What is the colour of the iron(III) precipitate

A

Orange-brown

19
Q

What is the colour of the copper(II) precipitate

A

Blue

20
Q

What is the colour of the calcium(2+) precipitate

A

white

21
Q

What is the colour of the zinc(II) precipitate

A

white

22
Q

What is the different between calcium hydroxide and zinc hydroxide

A

Zinc hydroxide dissolves to form a colourless solution but calcium hydroxide doesn’t dissolve.

23
Q

What is another test for metal hydroxides

A

Take the metal and add a few drops of sodium hydroxide

24
Q

What are the steps for flame test

A

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.

25
Q

How to detect sulphate ions

A

Barium ions react with sulphate ions to produce white, insoluble barium sulphate.
Ba 2+ + SO 2- 4 -> BaSO4

26
Q

How do you do the test for sulphate ions

A

Add a few drops of HCl
then add a few drops of barium chloride solution

27
Q

How do you detect carbonate ions

A

Hydrogen ions from dilute acids react with carbonate ions to produce carbon dioxide and water
2H+ + CO2- 3 -> CO2 + H2O

28
Q

How do you do the test for carbonate ions

A

Add a few drops of HCL
If carbonate ions are present, bubbles of gas will be produced. You can confirm that the fas is CO2 by bubbling it through limewater

29
Q

How to detect halide ions

A

Silver fluorides is soluble in water, but the other silver halides are insoluble. This forms the basis of a simple laboratory tests to detect chloride, bromide and iodide ions in solution.

30
Q

How do you do the test for halide ions

A

Add a few drops of dilute nitric acid
Then add a few drops of silver nitrate solution, AgNO3 (aq)

31
Q

What are the colours of the precipitates produced

A

Chloride , white
Bromide, cream
Iodide, yellow

32
Q

What is instrumental method of analysis

A

An instrumental method of analysis relies on a machine to carry out an analysis of a substance.

33
Q

What are the advantages of instrumental methods of analysis

A

Sensitivity - instruments can analyse very small amounts of substances. This is useful if the substances are expensive or difficult to get.
Accuracy - Instruments are very accurate. They can be calibrated using internationally accepted standards.
Speed - instruments can carry out analyses quickly and they can run all the time

34
Q

What does each peak represent in the chromatogram

A

A substance present in the mixture

35
Q

What do the areas under each peak show

A

The relative amount of each substance in the mixture

36
Q

What is the retention time

A

The time taken to travel through the chromatography column is different for different substances.

37
Q

What does the mass spectrometer do

A

Measures the masses of the atoms and molecules. It is used to analyse the relative amount of different isotopes of an element and the structure of the molecules

38
Q

What does each peak represent

A

A fragment of a molecule

39
Q

What does the peak on the far right represent

A

The molecular ion

40
Q

What is the mass to charge ratio equal to

A

The Mr

OCR gcse ChEMisTry (16 decks)

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