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Chemistry > Topic 3 - chemical change > Flashcards

Topic 3 - chemical change Flashcards

1
Q

What is an acid?

A

A substance with a pH less than 7

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2
Q

What ions do acids form in water?

A

H+ ions

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3
Q

What is an alkali?

A

A base that is soluble in water. pH more than 7

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4
Q

What ions do alkalis form in water?

A

OH- ions (Hydroxide ions)

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5
Q

What is the pH of a neutral solution?

A

pH 7

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6
Q

What is an indicator?

A

A dye that changes colour depending on whether it’s above or below a certain pH.

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7
Q

Explain the effect of acidic, neutral and alkaline solutions on litmus

A

Red in acidic, purple in neutral, blue in alkaline

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8
Q

Explain the effect of acidic, neutral and alkaline solutions on methyl orange.

A

Red in acidic, yellow in neutral and alkaline solutions

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9
Q

Explain the effect of acidic, neutral and alkaline solutions on phenolphthalein

A

Colourless in acidic and neutral solutions, pink in alkaline

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10
Q

What’s the effect of increasing the concentration of hydrogen ions in an acidic solution?

A

The solution becomes more acidic so the pH decreases

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11
Q

What’s the effect of increasing the concentration of hydroxide ions in an alkaline solution?

A

The pH increases so becomes a stronger alkaline.

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12
Q

What happens to the pH of a solution when hydrogen ion concentration is increased?

A

As hydrogen ion concentration increases by a factor of 10, the pH of the solution decreases by 1

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13
Q

What does concentrated mean for an acid?

A

An acid with a large number of acid molecules compared to the volume of water

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14
Q

What does dilute mean for an acid?

A

An acid with a small number of acid molecules compared to the volume of water.

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15
Q

What are strong acids?

A

Acids that ionise almost completely in water ie. a large proportion of the acid molecules dissociate to release H+ ions.

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16
Q

What are weak acids?

A

Acids that don’t fully ionise in solution ie. only a small proportion of the acid molecules dissociate to release H+ ions.

17
Q

What is a base?

A

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

18
Q

What is a neutralisation reaction?

A

A reaction between an acid and a base

19
Q

What is the chemical test for hydrogen?

A

Use a lighted splint and if hydrogen is present you will hear a squeaky pop due to hydrogen burning with oxygen in the air to form water.

20
Q

What is the chemical test for carbon dioxide using limewater?

A

To see if a gas is carbon dioxide bubble it through with limewater. If the gas is carbon dioxide the limewater will turn cloudy.

21
Q

What happens in an acid-alkali neutralisation reaction?

A

Hydrogen ions (H+) from the acid react with hydroxide ions (OH-) from the alkali to form water.

22
Q

Why must titration be used if soluble salts are prepared from an acid + soluble reactant?

A

because there is no insoluble excess reactant that could be removed by filtration

23
Q

What common substances are soluble in water?

A

All common sodium, potassium + ammonium salts
All nitrates
Most common chlorides
Most common sulphates

24
Q

What common substances are insoluble in water?

A

Silver + lead chlorides
Lead, barium + calcium sulfate
Most common carbonates + hydroxides except those of sodium, potassium + ammonium

25
Q

Why is excess of the reactant added when making soluble salts prepared from an acid + an insoluble reactant?

A

So you don’t have any leftover acid in your product

26
Q

Why is the excess reactant removed when making soluble salts prepared from an acid + an insoluble reactant?

A

To get a solution containing only the salt and water

27
Q

Why must the acid + soluble reactant be mixed in the correct proportions when soluble salts are prepared from an acid + and a soluble reactant?

A

Because the salt is soluble and would be contaminated with the excess alkali

28
Q

Describe the method used to prepare a pure, dry sample of an insoluble salt

A

1- mix two suitable solutions
2- use filtration to separate precipitate as a residue from solution
3- wash precipitate with distilled water while it’s in the filter funnel
4- leave washed precipitate aside or in warm oven to dry

29
Q

How is a salt formed?

A

During a neutralisation reaction (a reaction between an acid + base)

30
Q

What salts do the general acids produce?

A

Hydrochloric acid produces chloride salts
Sulfuric acid produces sulfate salts
Nitric acid produces nitrate salts

31
Q

Explain the general reactions of aqueous solutions of acids with metals

A

Acid + metal -> salt + hydrogen

Eg 2HCl + Mg -> MgCl2 + H2

32
Q

Explain the general reactions of aqueous solutions of acids with metal oxides

A

Acid + metal oxide -> salt + water

Eg 2HCl + CuO -> CuCl2 + H2O

33
Q

Explain the general reactions of aqueous solutions of acids with metal hydroxides

A

Acid + metal hydroxide -> salt + water

Eg HCl + NaOH -> NaCl + H2O

34
Q

Explain the general reactions of aqueous solutions of acids with metal carbonates

A

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

Eg 2HCl + Na2CO3 -> 2NaCl + H2O + CO2

Chemistry (15 decks)

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