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Chemistry Paper 1 > C3 - Chemical Changes > Flashcards

C3 - Chemical Changes Flashcards

1
Q

Which ions make aqueous solutions acidic?

A

Hydrogen ions (H+)

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2
Q

Which ions make aqueous solutions alkaline?

A

Hydroxide ions (OH-)

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3
Q

What colour is phenolphthalein in an acid and alkali?

A

Acid - Colourless

Alkali - Pink

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4
Q

What colour is methyl orange in an acid and an alkali?

A

Acid - Red

Alkali - Yellow

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5
Q

What colour is litmus paper in an acid and an alkali?

A

Acid - Red

Alkali - Blue

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6
Q

Acid X has a pH of 1. What can you say about the concentration of hydrogen ions in acid X?

(HT)

A
  • There is a high concentration of hydrogen ions, making it a strong acid
  • The lower the pH of the acid, the higher the concentration of H+ ions
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7
Q

Alkali Y has a pH of 8.5, what can you say about the concentration of hydroxide ions in alkali Y?

(HT)

A
  • Low concentration of hydroxide ions in the alkali, making it a weak alkali
  • The lower the pH of the alkali, the lower the concentration of OH- ions
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8
Q

What happens to the concentration of Hydrogen ions if the pH decreases by one unit?

A

The hydrogen ion concentration increases by a factor of 10.

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9
Q

What is a neutralisation reaction?

What happens during an acid-alkali neutralisation reaction?

A
  • A reaction between an acid and a base.

- H+ ions from the acid react with the OH- ions from the alkali to form water.

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10
Q

What is the ionic equation for a neutralisation reaction?

A

H+ (aq) + OH- (aq) ——> H2O (l)

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11
Q

What does concentrated and dilute mean in terms of an acid?

A

Concentrated acids have more moles of acid per unit volume of water than dilute acids.

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12
Q

What is a strong/weak acid?

A

Strength of an an acid refers to whether the acid completely dissociates in water or not.

  • Strong acid = fully dissociates in aqueous solution
  • Weak acid = partially dissociates in aqueous solutions
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13
Q

An acid only partially dissociates in water. What can be said about the strength of the acid?

A
  • It is a weak acid
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14
Q

What is a base?

A

Any substance that reacts with an acid to form salt and water only

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15
Q

‘Alkalis are insoluble bases’

True or False?

A

False! Alkalis are soluble bases

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16
Q

What are the products when an acid reacts with a metal?

A

Salt and Hydrogen

acid + metal ——> salt + hydrogen

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17
Q

What are the products when an acid reacts with a metal oxide?

A

Salt and Water

acid + metal oxide ——> salt + water

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18
Q

What are the products when an acid reacts with a metal hydroxide?

A

Salt and Water

acid + metal hydroxide——> salt + water

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19
Q

What are the products when an acid reacts with a metal carbonate?

A

Salt, Water and Carbon Dioxide

acid + metal carbonate ——> salt + water + carbon dioxide

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20
Q

Why are metal oxides normally bases rather than alkalis?

A
  • Metal oxides are normally insoluble.

- Alkalis are soluble

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21
Q

Describe the chemical test for hydrogen.

A

Insert lit splint into test tube of gas

If hydrogen is present a ‘squeaky pop’ will be heard

22
Q

Describe the chemical test for carbon dioxide.

A

Bubble the gas through limewater.

Limewater turns cloudy/milky in the presence of carbon dioxide

23
Q

An acid only partially dissociates in water. What can be said about the strength of the acid?

A
  • It is a weak acid
24
Q

What is a base?

A

Any substance that reacts with an acid to form salt and water only

25
Q

‘Alkalis are insoluble bases’

True or False?

A

False! Alkalis are soluble bases

26
Q

What are the products when an acid reacts with a metal?

A

Salt and Hydrogen

acid + metal ——> salt + hydrogen

27
Q

What are the products when an acid reacts with a metal oxide?

A

Salt and Water

acid + metal oxide ——> salt + water

28
Q

What are the products when an acid reacts with a metal hydroxide?

A

Salt and Water

acid + metal hydroxide——> salt + water

29
Q

What are the products when an acid reacts with a metal carbonate?

A

Salt, Water and Carbon Dioxide

acid + metal carbonate ——> salt + water + carbon dioxide

30
Q

Why are metal oxides normally bases rather than alkalis?

A
  • Metal oxides are normally insoluble.

- Alkalis are soluble

31
Q

Describe the chemical test for hydrogen.

A

Insert lit splint into test tube of gas

If hydrogen is present a ‘squeaky pop’ will be heard

32
Q

Describe the chemical test for carbon dioxide.

A

Bubble the gas through limewater.

Limewater turns cloudy/milky in the presence of carbon dioxide

33
Q

When a soluble salt is prepared from an acid and an insoluble reactant, why is excess of the insoluble reactant added?

A

To ensure all the acid reacts

34
Q

How is the excess reactant removed when a soluble salt is prepared from an acid?
Why?

A

By filtration.

It is removed to leave a pure solution of the salt.

35
Q

What method must be used to prepare a salt from an acid and a soluble reactant?
Why?

A
  • Titration
  • Since both reactants are soluble, a titration allows you to combine the reactants exactly and avoid adding an excess of either reactant as this would be hard to remove.
36
Q

3 steps when producing pure dry salt from an acid and alkali.

A
  1. Complete a titration to find volume of acid that reacts exactly with a set volume of alkali
  2. Use results from titration to mix acid and alkali in correct proportions
  3. Evaporate the water from the solution, leaving pure dry salt crystals
37
Q

Describe how to carry out an acid-alkali titration.

A
  1. Use a pipette to add measured volume of acid to conical flask and add a few drops of indicator.
  2. Fill burette with the alkali, noting the volume.
  3. Add alkali to conical flask. Try to find end point (at which indication first changes colour).
  4. Repeat, adding the alkali drop by drop near the end point and swirling flask to mix.
  5. Record the final volume in burette and repeat experiment.
38
Q

Most chlorides are soluble. What are the two exceptions?

A

Silver Chloride and Lead Chloride are insoluble.

39
Q

‘All nitrates are soluble’

True or false?

A

True.

40
Q

Most common surfaces are soluble. What are the 3 exceptions?

A

Lead Sulfate, Calcium Sulfate and Barium Sulfate are insoluble.

41
Q

What salts produced when lead reacts with sulfuric acid? Will a precipitate form?

A

Lead Sulfate.

Yes a precipitate will form because lead sulfate is insoluble.

42
Q

How do you prepare a pure, dry sample of an insoluble salt?

A
  1. Mix the two solutions required to form salt.
  2. Filter mixture using filter paper
  3. Residue on filter paper is the insoluble salt
  4. Wash the salt with distilled water and leave to dry.
43
Q

What is an electrolyte?

A

An ionic compound in its molten or aqueous state.

44
Q

Why can an electrolyte conduct electricity?

A

An ionic compound that is in its molten or aqueous state has mobile ions allowing them to carry charge.

45
Q

What is electrolysis?

A

A process which uses electrical energy (from a direct current supply) to decompose electrolytes.

46
Q

Where do charged ions in the electrolyte move to during electrolysis?

A
  • Cations (positive ions) move toward the cathode (negative electrode)
  • Anions (negative ions) move towards the anode (positive electrode)
47
Q

What happens at the anode during electrolysis?

A

The anions (negatively charged ions) lose electrons to form their elements.

48
Q

What happens to the cathode during electrolysis?

A

Cations (positively charged ions) gain electrons to form their elements.

49
Q

Name the processes that occur at each electrode during electrolysis.
(HT)

A

Anode (positive) - oxidation

Cathode (negative) - reduction

50
Q

What is formed at each electrode in electrolysis?

A

Positive electrode: Non metal

Negative electrode: Metal or Hydrogen

51
Q

How can you predict whether a metal or hydrogen will form at the negative electrode?

A

If hydrogen is above the metal in the reactivity series then the metal will form.

If the metal is more reactive than the hydrogen then hydrogen will form.

52
Q

What is formed at each electrode during the electrolysis of copper chloride solution?

A

Positive electrode: Chlorine

Negative electrode: Copper

Chemistry Paper 1 (5 decks)

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