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GCSE chemistry > Chemical Changes > Flashcards

Chemical Changes Flashcards

1
Q

Which ions make aqueous solutions acidic?

A

Hydrogen ions

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2
Q

Which ions make aqueous solutions alkaline?

A

Hydroxide ions

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3
Q

What is the pH scale?

A

The pH scale ranges from pH 0 to pH 14 and measures the acidity or alkalinity of a solution

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4
Q

What are pH ranges for acids and alkalis?

A

Acid - less than pH 7, Neutral - pH 7, Alkali - greater than pH 7

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5
Q

What can be used to measure pH?

A

Universal indicator and pH probe

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6
Q

What colour is phenolphthalein in acid and alkali?

A

Acid - colourless and Alkali - Pink

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7
Q

What colour is methyl orange in acid and alkali?

A

acid - red and Alkali - yellow

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8
Q

What colour is blue litmus paper in acid and alkali?

A

Acid - turns red and Alkali - stays blue

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9
Q

What colour is red litmus paper in acid and alkali?

A

Acid - stays red and Alkali - turns blue

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10
Q

What’s a problem with using universal indicator to test the path of a solution?

A

The colour of the solution is matched to a pH colour chart, this is quite subjective as people may disagree with which colour the solution matches and it doesn’t provide an exact pH value

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11
Q

If pH decreases by one unit, what happens to the concentration hydrogen ions?

A

The hydrogen ion concentration increases by a factor of 10

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12
Q

What is a neutralisation reaction?

A

Reaction between an acid and a base (in an acid-alkali neutralisation reaction H+ ions from the acid react with OH- ions from the alkali to form water

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13
Q

What is the ionic equation for a neutralisation reaction?

A

H+ + OH- -> H2O

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14
Q

What does concentrated and dilute mean when talking about acid?

A

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

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15
Q

What is a weak acid?

A

An acid that has partially dissociated in water

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16
Q

What is a strong acid?

A

An acid that has fully dissociated in water

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17
Q

What is a base?

A

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

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18
Q

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

A

Acid + metal -> Salt and hydrogen

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19
Q

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

A

Acid + metal oxide -> salt + water

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20
Q

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

A

Acid + metal hydroxide -> salt + water

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21
Q

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

A

Acid + metal carbonate -> salt + water + carbon dioxide

22
Q

Why are metal oxides normally bases rather than alkalis?

A

Metal oxides are normally insoluble

23
Q

What is the name of the salt formed from magnesium and sulphuric acid?

A

Magnesium sulfate

24
Q

What is the name of the salt formed from zinc oxide and nitric acid?

A

Zinc nitrate

25
Q

What is the name of the salt formed from calcium carbonate and hydrochloric acid?

A

Calcium chloride

26
Q

What is the chemical test for hydrogen?

A

Insert a lot splint into a test tube of gas and a spewky pop will be heard if hydrogen is present

27
Q

What is the chemical test for carbon dioxide?

A

Bubble the gas through limewater and limewater turns cloudy if carbon dioxide is present

28
Q

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

A

By filtration, to leave a pure solution of the salt

29
Q

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

A

Titration, since both the reactants are soluble, a titration allows you to combine the reactants exactly and avoid adding an excess of either reactants as this would be hard to remove

30
Q

What 3 steps are required when producing a pure dry salt from an acid and alkali?

A

Complete a titration to find the volume of acid that reacts exactly with a set volume of alkali, use the results from the titration to mix the acid and alkali in the correct proportions and evaporate the water from the solution, leaving pure dry salt crystals

31
Q

How do you carry out an acid-alkali titration?

A

Use a pipettes to add a measured volume of acid to the conical flask then add a few drops of indicator, place on a white tile, fill the butter with the alkali, noting the initial volume, add the alkali to the conical flask, first complete a rough trial to find the end point, repeat, adding the alkali drop by drop near the end point and swirling the flask constantly to mix and record the final volume in the bursts, repeat until you have concordant results

32
Q

What are the exceptions from chlorides being soluble?

A

Silver chloride and lead chloride

33
Q

Are nitrates soluble?

A

Yes

34
Q

Are sodiums, potassiums and ammonium salts soluble?

A

Yes

35
Q

What are the exceptions from sulfates being soluble?

A

Lead, calcium and barium sulfate

36
Q

What are the exceptions from carbonates and hydroxides being insoluble?

A

Sodium, potassium and ammonium

37
Q

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

A

Mix two solutions required to form the salt, filter the mixture using filter paper, the residue on the filter paper is the insoluble salt and wash the salt with distilled water and leave to dry

38
Q

What is an electrolyte?

A

An ionic compound in its molten or aqueous state

39
Q

Why can an electrolyte carry charge?

A

An ionic compound in is molten or aqueous state has mobile ions which can carry charge

40
Q

What is electrolysis?

A

A process which uses electrical energy to decompose electrolytes

41
Q

What are cathode and anode?

A

Cathode - negative electrode and Anode - positive electrode

42
Q

Where do charged ions in the electrolytes move to during electrolytes?

A

Cations move towards the cathode and anions move towards the anode

43
Q

What happens at the anode during electrolysis?

A

The anions lose electrons to form their elements

44
Q

What happens at the cathode during electrolysis?

A

Cations gain electrons to form their elements

45
Q

What are the processes that occur at each electrode during electrolysis?

A

Oxidation and Reduction

46
Q

What is formed at each electrode in electrolysis?

A

Positive electrode: non-metal and negative electrode: metal or hydrogen

47
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

48
Q

What does oxidation mean?

A

Loss of electrons

49
Q

What does reeducation mean?

A

Gain of electrons

50
Q

How can electrolysis of copper sulfate can be used to purify copper?

A

Place 2 copper electrodes into copper sulfate solution, the anode should be impure copper and cathode should be pure copper, connect to a power supply and the copper in the impure anode is pulled towards the cathode to form pure copper, impurities form as sludge below the anode, Cu2+ ions from copper sulfate remain in solution

GCSE chemistry (8 decks)

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