3 Elements and compounds Flashcards

1
Q

Define an element

A

A substance containing only one type of atom

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2
Q

Define a compound

A

A substance containing two or more different types of atoms chemically bonded together

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3
Q

Write the chemical equation for the decomposition of H2O2

A

2H2O2 –> 2H2O + O2

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4
Q

What is a molecule?

A

When two or more atoms are chemically bonded together

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5
Q

What is the word equation for the decomposition of hydrogen peroxide

A

hydrogen peroxide –> water + oxygen

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6
Q

How can you prepare oxygen in the lab?

A
  • Add hydrogen peroxide (H2O2) to a conical flask.
  • Connect a bung with tubing to the top of the conical flask.
  • Fill a trough with water
  • Submerge two or three test tube in the water removing all the air from them
  • Arrange each of them upside down filled with water- ready to bubble oxygen into them
  • Remove the bung and add a small spatula of manganese dioxide (catalyst) and quickly replace the bung.
  • Allow a small amount of bubbles to escape before you start collecting the pure oxygen by down ward displacement.
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7
Q

What type of reaction is this?

2H2O2 –> 2H2O + O2

A

decomposition

A –> B + C

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8
Q

What would you observe during the decomposition of hydrogen peroxide using the catalyst manganese dioxide?

A

Fizzing

manganese dioxide is not used up

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9
Q

What is the name of the method used to collect oxygen druring the decomposition of hydrogen peroxide?

A

Downward displacement of water

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10
Q

What is the test for oxygen?

A

glowing splint

relights

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11
Q

How can you make carbon dioxide in a lab?

A
  • Add a sample of CuCO3 in a test tube.
  • Add a bung and delivery tube to the end of the test tube
  • Collect the carbon dioxide by upward displacement of air by placing the delivery tube into an upright test tube.

NOTE: CO2 is more dense than air and will fill the test tube- pushing the air out.

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12
Q

What is the test for carbon dioxide?

A

bubble through limewater

limewater turns cloudy

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13
Q

Write the word equation for the reaction thermal decomposition of copper (II) carbonate

A

copper (II) carbonate –> copper oxide + carbon dioxide

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14
Q

Write the word equation for the combustion of magnesium.

A

combustion means reaction with oxygen

magnesium + oxygen –> magnesium oxide

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15
Q

What is the chemical equation for the thermal decomposition of copper (II) carbonate?

A

CuCO3 –> CuO + CO2

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16
Q

What type of reaction is this?

2Ba + O2 –> 2BaO

A

reaction with oxygen so it is called combustion or oxidation

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17
Q

Why can’t we collect carbon dioxide by downward displacement of water?

A

Carbon dioxide is soluble in water- some of it will dissolve in the water

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18
Q

What would you observe when you burn magnesium in oxygen?

A

grey solid turns to a white powder

very bright light

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19
Q

How can we collect the gas carbon dioxide?

A

Upward displacement of air

CO2 is more dense than air and will fill an upright test tube- pushing (displacing) the air up and out.

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20
Q

Is this reaction endothermic or exothermic?

Magnsium + oxygen –> magnesium oxide

A

exothermic - both heat and light are given off

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21
Q

Write the word equation for the combustion of sulfur

A

sulphur + oxygen –> sulfur dioxide

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22
Q

What would you observe if you plunge a metal oxide into water with a few drops of universal indicator?

A

The indicator will turn blue as metal oxides are alkaline

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23
Q

Write the chemical equation for the combusiton of sulfur

A

S + O2 –> SO2

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24
Q

What would you observe if a non-metal oxide were added to water with a few drops of universal indicator?

A

It would turn red

non-metal oxide in water forms an acid

H+ ions are present

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25
Q

When sulfur burns in oxygen, what is the colour of the flame?

A

blue

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26
Q

What are the three oxides which form in a car engine?

A

sulfur in fuel form sulfur dioxide

nitrogen in air forms nitrous oxide

carbon in fuel form carbon dioxide

These all cause the rain to be acidic -acid rain

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27
Q

What is the most abundance substance in air after nitrogen and oxygen?

A

argon

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28
Q

List two gases which contribute to the greenhouse effect

A

carbon dioxide is a green house gas

so is methane!!

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29
Q

What is the percentage of nitrogen in air?

A

78%

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30
Q

What is the percentage of oxygen in air?

A

21%

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31
Q

When finding the percentage of oxygen in air copper turning are used. Why must the copper be in excess? (You have much more copper than needed for the reaction)

A

You are measuring the percentage of oxygen in air by reacting it with a metal. To get all the oxygen to react you need excess copper.

When heated in air copper will turn from orange/pink to black as copper oxide is formed

Eventually all the oxygen will be used up, allowing you to measure the remaining gases in air.

32
Q

Below are the results from the percentage of oxygen in air experiment using copper turnings

  • Starting volume 100 cm3
  • End volume 79 cm3

Find the percentage of oxygen in air

A

(100 - 79) / 100 = 21%

33
Q

What is the valency of the hydroxide ion?

A

OH 1-

34
Q

Describe the set-up for measuring the percentage of oxygen in air with copper turnings.

A
  • Two syringes with glass tubing between.
  • Excess copper turnings placed in the middle of the tube.
  • Start with exactly 100 cm3 of air by reading the syringe volume at eye level.
  • Heat the glass tube under the copper turnings using a roaring flame.
  • Push the air from one syringe to another repeatedly until the volume no longer changes- all the oxygen has been used up.
  • Allow the gas to cool before reading the new volume of gas.
  • ((Starting volume - final volume) /starting volume) x 100= percentage oxygen in air
35
Q

What are the atoms in group 7 called?

A

Halogens

36
Q

What is the colour change of the copper turnings in the percentage of oxygen in air experiment?

A

orange/pink to black

37
Q

What is the valency of the sulfate ion?

A

SO4 2-

38
Q

Why do we need the gas to cool before taking the final volume reading in the percentage of oxygen in air experiment?

A

gas expands when heated.

Fair test.

39
Q

What is the valency of the ammonium ion?

A

NH4 +

40
Q

Percentage of oxygen in air can be measured using the reaction of copper with oxygen or the reaction of iron wool and oxygen. What is the main difference with these two experiments?

A

Percentage of oxygen in air can be done more quickly using copper turnings. Copper is heated using a roaring flame.

Percentage of oxygen in air is much slower (1-2 weeks) when using iron wool. Rusting is a very slow reaction.

41
Q

What are the elements in group 1 called?

A

Alkaline metals

42
Q

What is the valency of the carbonate ion?

A

CO3 2-

43
Q

What are the metals in group 2 called?

A

Alkaline Earth metals

44
Q

Name the only two elements which are liquid at room temperature

A

bromine and mercury

45
Q

What are the elements in group 0 called?

A

Noble gases

46
Q

What is special about the transistion metals?

A

They form colourful compounds

They have more than one valency

Fe2+ Fe3+

47
Q

Complete the reaction of iron with sulfur

iron + sulfur –>

A

iron + sulfur –> iron sulphide

48
Q

Name the diatomic elements

A

Hydrogen

Nitrogen

Fluorine

Oxygen

Iodine

Chlorine

Bromine

49
Q

Name the compound

NH4OH

A

ammonium hydroxide

50
Q

Name the compound

Na2CO3

A

sodium carbonate

51
Q

Name the compound

MgSO4

A

Magnesium sulfate

52
Q

Name the compound

Ca(NO3)2

A

calcium nitrate

53
Q

Name the compound

FeS

A

Iron sulfide

54
Q

A metal oxide which can dissolve in water will turn universal indicator __________________ because it is _________________

A

A metal oxide which can dissolve in water will turn universal indicator blue because it is alkaline

55
Q

What does accurate mean?

A

close to the true value

56
Q

A non-metal oxide added to water will turn universal indicator ______________ because it is an ____________

A

A non-metal oxide added to water will turn universal indicator red because it is an acid

SO2 in water form H2SO4

57
Q

What is an anamolous result?

A

A result which does not fit the pattern

58
Q

What should you do with an anamolous result?

A

record it but cross it out and carry out another reading- do not include it in an average

59
Q

How should you measure the volume of a liquid in a measuring cylinder accurately?

A
  • Place the measuring cylinder on a flat and level surface
  • Read the volume at eye level and the bottom of the meniscus
60
Q

Describe what a precise instrument is

A

An intrument that gives readings with more decimal places or an instrument with smaller increments (resolution)

Some measuring cylinders read to +- 1 cm3

Some measuring cylinders read to +- 0.2 cm3

61
Q

What would the colour change be for the rusting of iron in the percentage of oxygen experiment?

A

grey to red/brown

62
Q

How do you know when reading are reliable?

A

When the readings are all very similar or clustered closely

63
Q

Name gases which contribute to the greenhouse effect

A

carbon dioxide and methane

64
Q

A dometic boiler is used to heat homes. It burns methane in oxygen. It has the following sign near the opening to the boiler. What does this sign mean in terms of combustion?

A

A yellow flame indicates that the flame is not getting enough oxygen.

This means incomplete combustion is occuring which produces carbon monoxide

Carbon monoxide is toxic

65
Q

Which letter/s show a pure element?

A

E, F and H

Element contains only one type of atom.

66
Q

Which letter/s show a mixture of compounds

A

G

Each substance contains two or more different atoms which are chemically bonded.

67
Q

Which letter/s show a mixture of elements?

A

B

A mixuture contains two or more different substances which are not chemically bonded.

68
Q

Which letter/s show a pure compound?

A

A, D and I

Compound is a substance containing two or more different atoms chemically bonded together.

69
Q

Which method would be suitable to collect carbon dioxide?

A

1st method- upward displacment of air

Carbon dioxide is more dense than air. It will displace the air upward

70
Q

What gas is being produced in the following method?

oxygen

hydrogen

carbon dioxide

A

carbon dioxide

It is more dense than air and will displace air upward- or fall into the test tube.

71
Q

Which method would be suitable to collect hydrogen?

A

2nd method- downward displacement of air

Hydrogen is less dense than air. It will rise into the container and displace the air downward

72
Q

Which method would be suitable to collect carbon dioxide?

A

1st method- upward displacment of air

Carbon dioxide is more dense than air. It will displace the air upward

73
Q

Which method would be suitable to collect oxygen?

A

3rd method- downward displacement of water

It has a similar density to air so method 1 or 2 will not work. Oxygen is less dense than water. It will bubble up into the tube displacing the water downward.

74
Q

white phosphorus can be used to measure the percentage of oxygen in air.

  • top is open, phosphorus is touched with a hot metal rod, top is closed
  • phosphorus burns in oxygen and water level rises.

What is the chemical equation for phosphorus burning in oxygen?

A

4P (s) + 5O2 (g) ⇒ 2P2O5 (s)

75
Q

Wet iron wool can be used to find the percentage of oxygen in air

  • place wet iron filings in end of burette
  • turn upside down in water trough
  • close stopper
  • leave for several days

How do you know when all the oxygen has been used up?

A

The water level no longer changes

This reaction is very slow so several days is needed plus excess iron

76
Q

metal oxides are basic

If they can dissolve in water, what will they form?

A

alkaline solution

77
Q

Non-metal oxides usually dissolve in water.

What sort of solution do they form?

A

acidic solutions

e.g. SO2 in water forms sulfurous acid H2SO3