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Chemistry > Q3 - Other Experiments > Flashcards

Q3 - Other Experiments Flashcards

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1
Q

Flame tests:
Why do these metal salts give off a characteristic colour?

A

Each element has a unique atomic spectrum due to the fact that each element has its own arrangement of energy levels

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2
Q

Flame tests:
Give one practical application of flame tests?

A

Used to identify presence of certain metals

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3
Q

Flame tests:
Outline how to carry out a flame test

A
  1. Soak a wooden splint in water
  2. Dip splint in a sample of the salt
  3. Hold the salt over the hot / blue flame of a bunsen burner
  4. Note the colour of the flame
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4
Q

Flame tests:
Results

A

Lithium → crimson
Potassium → lilac
Barium → green
Strontium → red
Copper → blue-green
Sodium → yellow

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5
Q

Test for anions:
Define the term anion

A

A negatively charged ion

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6
Q

Test for anions:
Why is deionised water used in all the tests?

A

Tap water contains many dissolved ions, these ions could interfere with the test

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7
Q

Test for anions:
Test for chloride ions

A

• Add silver nitrate → white precipitate forms that is soluble in dilute ammonia

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8
Q

Test for anions:
Test for sulfate / sulfite

A

• Add barium chloride → white precipitate forms
• Add dilute HCl
↳ precipitate remains = sulfate
↳ precipitate dissolves = sulfite

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9
Q

Test for anions:
Test for carbonate / hydrogencarbonate

A

• Add dilute HCl
• Add MgSO4
↳ white precipitate = carbonate
↳ no precipitate = hydrogencarbonate

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10
Q

Test for anions:
Test for nitrate ions

A

brown ring test
• Add freshly prepared FeSO4
• Add concentrated sulfuric acid → brown ring forms at junction of two liquids

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11
Q

Test for anions:
Test for phosphate ions

A

• Add ammonium molybdate
• Add concentrated nitric acid & warm solution → yellow precipitate forms

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12
Q

To measure the RMM of a volatile liquid;
Define relative molecular mass

A

The average of the mass numbers of the isotopes of the element as they occur naturally taking their abundances into account, expressed on a scale in which atoms of the carbon 12 isotope have a mass of exactly 12 units

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13
Q

To measure the RMM of a volatile liquid;
What does the term volatile mean?

A

A liquid with a low boiling point

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14
Q

To measure the RMM of a volatile liquid;
Name a suitable liquid

A

Propanone
Cyclohexane
Ethanol

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15
Q

To measure the RMM of a volatile liquid;
Why must a very small hole be punctured in the aluminium foil?

A

To allow the excess vapour to escape from the flask

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16
Q

To measure the RMM of a volatile liquid;
What must be done to ensure all of the volatile liquid has vaporised fully?

A

The flash should be left in the boiling water for several minutes

17
Q

To measure the RMM of a volatile liquid;
Indicate a source of error in this experiment

A
  • measuring the volume of the flask inaccurately
  • not leaving the flash in boiling water for a sufficient amount of time
  • forgetting to ensure that the inside is the flash is clean and dry
18
Q

To measure the RMM of a volatile liquid;
Why does the liquid have to be volatile?

A

When the flask is placed in the boiling water the liquid will be completely changed into a gas and fill the conical flask

19
Q

Oxidation/reduction reactions;
Why are halogens suitable to use as oxidising agents?

A

They all have high electronegativity values
↳ they have a strong attraction for electrons and they remove electrons from other substances

20
Q

Rates of reaction;
Define the term catalyst

A

A substance that alters the rate of a chemical reaction but is not consumed in the reaction

21
Q

Rates of reaction;
Describe the appearance of manganese dioxide before use

A

Black powdery solid

22
Q

Rates of reaction;
Name the products of the decomposition of hydrogen peroxide

A

Water and oxygen

23
Q

Rates of reaction;
What does it mean that hydrogen peroxide is said to be ‘20 volume’

A

A certain volume of hydrogen peroxide would give off 20 times that volume when it decomposes

24
Q

Rates of reaction;
Describe the appearance of the manganese dioxide at the end of the reaction
Would you expect to see a change in appearance?

A

Black powdery solid
No, manganese dioxide acts as a catalyst and a catalyst is usually unchanged at the end of the reaction

25
Q

Rates of reaction;
Give one everyday use of manganese dioxide

A

Used in the manufacture of ‘dry’ batteries

26
Q

Effect of concentration on rate of reaction;
What is meant by the term concentration?

A

The amount of solute dissolved in a given volume of solution

27
Q

Effect of concentration on rate of reaction;
What is the purpose of placing an X on the paper?

A

It serves as a standard marker that helps us to determine the stage at which the same amount of sulfur has been precipitated for each experiment
↳ makes it a fair test

28
Q

Effect of concentration on rate of reaction;
Describe the appearance of the suspension formed

A

Cloudy yellow colour

29
Q

Effect of concentration on rate of reaction;
What element is responsible for the cloudy precipitate?
What other products are formed?

A

Element is sulfur
Other products are sodium chloride, Sulfur dioxide & water

30
Q

Effect of concentration on rate of reaction;
What happened to the rate of reaction as the concentration was decreased?

A

The rate also decreased

31
Q

Effect of concentration on rate of reaction;
Explain what it means that time and rate are inversely proportional

A

As time is increased the rate is decreased

32
Q

Effect of temperature on rate of reaction;
What is the variable in this experiment?

A

Temperature

33
Q

Effect of temperature on rate of reaction;
Why is a dilute solution of sodium thiosulfate used in this experiment?

A

So the measured times will not be too short at the higher temperatures

(Higher conc. would make reaction too fast, making it difficult to measure the rate)

34
Q

Effect of temperature on rate of reaction;
Why is the temperature taken after the hydrochloric acid is added?

A

Some cooling may have occurred on addition of the hydrochloric acid

35
Q

Effect of temperature on rate of reaction;
Why is a stop clock used in this experiment?

A

To accurately measure the time taken to obscure the cross

36
Q

Effect of temperature on rate of reaction;
The graph for temperature vs rate is a curve, unlike the linear graph for concentration vs rate, why is this so?

A

The rate of reaction is not directly proportional to the temperature

37
Q

Effect of temperature on rate of reaction;
Give two everyday examples of temperature affecting the range of reaction

A
  • food stored in fridge - cold temp slows down rate of decomposition
  • catalytic converters work most efficiently when heated as the various reactions are increased at higher temperatures
38
Q

Effect of temperature on rate of reaction;
Name and describe the gas given off when sodium thiosulfate reacts with HCl in this experiment

A

Sulfur dioxide is given off

Has a strong, pungent smell

Chemistry (22 decks)

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