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Chemistry Year 11 IGCSE > 2.7 - Acid, Bases and Salt preparation > Flashcards

2.7 - Acid, Bases and Salt preparation Flashcards

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1
Q

What is a salt?

A

A salt is a neutral chemical compound made by reacting an acid with a base or a metal. It consists of a cation and an anion.

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2
Q

What is the solubility trends of ionic compounds in water?

A

All sodium, potassium and ammonium compounds are soluble.

All nitrates are soluble

Most common chlorides are soluble, except lead (II) chloride and silver chloride.

Most common sulfates are soluble except Lead (II) sulfate, barium sulfate silver sulfate and calcium sulfate.

Most common carbonates are insoluble, except sodium, potassium and ammonium carbonates.

Most metal hydroxides are insoluble except sodium, potassium and ammonium hydroxides calcium hydroxide is slightly soluble in water.

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3
Q

What are the mixtures to make soluble salts?

A

Acid + Metal
Acid + Metal oxide or hydroxide
Acid + Carbonate

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4
Q

Explain the practical for making a soluble salt (Copper sulfate)?

A

Measure 50cm3 of dilute sulfuric acid into a beaker and heat it on a tripod and gauze using a Bunsen Burner.
Add spatula full of black copper(II) oxide and continue heating. If all the copper oxide disappears add more copper(II) oxide till there is some left in beaker. Stir mixture well so no more will react and there is enough to react with the acid present. When there is Copper(II) oxide left the acid has been neutralised.

Filter the excess copper(II) oxide and transfer the filtrate which is blue into an evaporating basin. Copper (II) sulfate formed.

Heat solution over Bunsen burner to boil off some of the water and concentrated solution.
Keep heating until a saturated solution is formed dip the glass rod into the solution. Crystals form on the glass rod then remove it and the solution is close to saturated crystals formed.

Stop heating the reaction mixture allow it to cool slowly at room tempreture so that large crystals can form.
Remove the blue crystals from reaction by filtration allow them to dry.

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5
Q

What is the eq. for the formation of Copper(II) sulfate crystals?

A

CuO + H2SO4 > CuSO4 + H20

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6
Q

How can Magnesium Sulfate crystals be formed?

A

Add excess magnesium to sulfuric acid does not have to be heated. Reaction will fizz keep adding magnesium till fizzing stops and there is magnesium left in the beaker, acid has reacted.

Mg + H2SO4 > MgSO4 + H2

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7
Q

What is the ew. for crystallising reaction of magnesium sulfate crystals?

A

MgSO4 + 7H20 > Mgso4 7H20

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8
Q

How do you know whether to heat the mixture?

A

Carbonates react with dilute acids in the cold as does magnesium. Most other substances need to be heated.

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9
Q

Why is there a need for a different method when making sodium pottasium and ammonium salts?

A

In the usual method add an excess of a solid to an acid then filter off the unreacted solid to make sure all of the acid is used up

The problem that all sodium potassium and ammonium compounds are soluble in water. The solid added to the acid would not only react with the acid but any excess would just dissolve in the water present nothing visible to filter. No simple way of seeing when you have added enough of the solid to neutralise the acid

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10
Q

How can sodium sulfate crystals be made?

A

25CM3 of sodium hydroxide solution transferred to conical flask using a pipette a few drops of methyl orange added as indicator. Dilute sulfuric acid is run in from the burette until indicator turns from yellow to orange. The volume of acid needed is noted same with volumes of acid alkalis are mixed together in a clean flask without indicator.

Formation of the solution is: 2NaOH(aq) + H2SO4 > Na2SO4 + 2H20

Solution is heated to evaporate some water until saturated solution is formed left to cool so crystals form.
Crystals are finally seperated from any remaining solution by filtration
Crystals are dried by leaving in warm place.

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11
Q

How to make Sodium Chloride crystals?

A

NaOH + HCL > NaCL + H2O
Need titration using dilute hydrochloric acid rather than dilute sulfuric acid. follow same procedure

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12
Q

How to make Ammonium sulfate crystals?

A

Using ammonium solution rather than sodium hydroxide solution makes no difference to the method simple ammonium salts don’t have water of crystallisation still crystallise rather than evaporating

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13
Q

How to make Insoluble salts?

A

Basic procedure is to mix solutions of two soluble salts to form an insoluble salt and a solution of a soluble one.

It is called a precipitation reaction. A precipitate is a solid that if formed by a chemical reaction involving liquid or gases. A precipitation reaction is simply a reaction that produces preciptate

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14
Q

Explain the production of an insoluble salt for Silver chloride?

A

To make insoluble silver chloride was to mix together solutions of silver nitrate and sodium chloride.

Silver nitrate solution contains silver ions and nitrate ions in solution. The positive and negative ions are attracted they aren’t strong enough to stick together/ When mixing the two solutions the various ions meet when silver ions meet chloride ions the attractions aren’t so strong that the ions clump and form a solid. The sodium and nitrate ions remain in solution because they aren’t sufficiently attracted to each other.

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15
Q

What is needed to mix to make insoluble salts?

A

Mix 2 solutions containing soluble salts.

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16
Q

How can Barium Sulfate be made?

A

Barium nitrate solution and pottasium sulfate solution

Ba(NO3)2 + K2SO4 > BaSO4 + 2KNO3

Barium sulfate is a white precipitate

17
Q

Explain the practical to prepare a pure dry sample of Lead Sulfate?

A

Take 25cm3 of a solution of lead nitrate in a beaker and add 25cm3 of a solution of sodium sulfate. A white precip of lead sulfate will form.
Reaction mixture is filtered a white residue of lead (II) sulfate is left in filter paper and colourless solution of sodium nitrate is left in the filter paper any any excess reactants like sodium sulfate passes through into beaker or conical flask. White residue on filter paper is compound but it is contaminated with solutions of sodium nitrate

Wash the residue with distilled water pour 20cm3 into filter paper allow it to filter in the paper. Washes everything away apart from insoluble lead (II) sulfate. Should be repeated several times to make sure the sample is not contaminated

Transferthe filter paper and lead(II) sulfate to a warm oven to dry

Must wash the lead sulfate with distilled water if washing with tap water and then transfers to our sample to the oven water will evaporate leaving behind the dissolved solids from the water

18
Q

How would a salt be made if it wasn’t soluble?

A

Use a precipitation method. Mix two solutions one containing correct positive ion and the other the correct negative ion

19
Q

How would a salt be made if it was soluble but not sodium pottasium or ammonium salt?

A

React an acid with an excess of a solid metal, metal oxide hydroxide or carbonate.

20
Q

How would a salt be made if it was soluble but sodium pottasium or ammonium salt?

A

Use titration method. React an acid with a solution of sodium or potassium hydroxide or carbonate.

21
Q

What are all the main acids their formulas their salts and name of salts?

A

Hydrochloric acid, formula: HCl, Example of salt: NaCl, Name of salts: Chlorides
Nitric acid, formula: HNO3, Example of salt: KNO3, Name of salts: nitrates
Sulfuric acid, formula: H2S04, Name of salts: Sulfates
Ethanoic acid, formula: CH3COOH, Example of salt: CH3COONa, Name of salts ethanoates

22
Q

How do acids react with metals?

A

Simple dilute acids react with metals depending on their positions in reactivity series
Metals below hydrogen in the series dont react with dilute acids
Metals above hydrogen in the series react to produce hydrogen
The higher the metal in the reactivity series, the more vigorous the reaction. Never mix metals such as sodium or potassium with acids because reactions are too violent

Metal + acid > salt + hydrogen

23
Q

How does magnesium react with dilute dilute sulfuric acid?

A

There is rapid fizzing and a colourless gas is evolved, which pops with a lighted splint. The reaction mixture becomes very warm as heat is produced. The magnesium gradually disappears to leave a colourless solution of magnesium sulfate

Mg + H2O4 > MgSO4 + H2
Displacement reaction. More reactive magnesium displaces the less reactive hydrogen.

Reaction between Magnesium and hydrochloric acid is the same only magnesium chloride is formed.

24
Q

How does Zinc react with acids?

A

Reactions between zinc and other acids is same reactions is slower because Zinc is lower down

25
Q

What are bases?

A

Bases are substances that neutralise by combining with the hydrogen ions in them to produce water

26
Q

How do acids react with bases?

A

Metal oxides, such as copper (II) oxide and magnesium oxide are bases.

27
Q

How does Copper oxide react with sulfuric acid?

A

Copper (II) Oxide reacts wit hot dilute sulfuric acid to produce a blue solution of copper (II) Sulfate
All the metal oxide and acids combine behave in same reaction between copper oxide and dilute sulfuric acid produces a salt and water. Need to be heated to start.
Copper oxide is an ionic compound containing the O2- ion. What has happened in this reaction is that the H+ ions from the acid have combined with O2- ions to form water.

Metal oxide + acid > salt + water
Neutralisation reaction base neutralise the acid.

28
Q

How Do metal oxides react in water?

A

Some metal oxides are soluble in water and react with it o form solutions of metal hydroxides.

All group 1 oxides do this reaction, so for potassium oxide
k2O + H2O > 2KOH
Most other metal oxides are not soluble in water.
Calcium oxide dissolves lightly to form calcium hydroxide
CaO + H20 > Ca(OH)2

29
Q

How does dilute hydrochloric acid react with sodium hydroxide solution?

A

Metal hydroxide + acid > salt + water

Mixing sodium hydroxide solution and dilute hydrochloric acid produces a colourless not much happened. Repeat the reaction with a thermometer in the beaker, tempreture rises several degrees, showing chemical changes. Sodium chloride solution formed
NaOH + HCl > NaCl +H20
All neutralisation reactions for an acid reacting with an alkali have the same ionic equation they all involve the hydroxide ones from the alkali reacting with H+ ions from the acid to form water

30
Q

How do acids react with carbonates?

A

Carbonates react with cold dilute acids to produce carbon dioxide gas

31
Q

How does copper carbonate and dilute acids react?

A

Green copper carbonate reacts with common dilute acids to give a blue or blue - green solution of copper sulfate, copper nitrate or copper chloride. carbon dioxide given off. turns limewater.

CuCO3 + H2SO4 > CuSO4 + CO2

32
Q

How does sodium carbonate react with dilute acids?

A

Sodium carbonate is soluble in water.
Na2CO3 + 2HCl > 2NaCl + CO2 + H2O

Chemistry Year 11 IGCSE (20 decks)

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