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Chemistry > Unit 8 > Flashcards

Unit 8 Flashcards

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1
Q

How can you tell if something is acidic

A

By how it affects litmus. Litmus is a purple dye. It can be used as a solution, or on paper.
Acids turn Litmus red

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2
Q

How can you tell if something is an alkali

A

It turns the litmus blue

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3
Q

What is litmus

A

It is an indicator because it indicates if something that is an alkali or acidic

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4
Q

And example of a substance that is neutral

A

Water

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5
Q

pH less than 7

A

Acidic

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6
Q

pH more than 7

A

Alkaline

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7
Q

pH that is exactly 7

A

Neutral

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8
Q

What makes acidic solutions acidic

A

Hydrogen ions

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9
Q

In a solution of strong ions

A

All molecules become ions.

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10
Q

In solution of weak acids

A

Only some molecules become acids

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11
Q

What does the higher concentration of hydrogen ions mean

A

The lower the pH and the stronger the acid

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12
Q

What does an alkaline solution contain

A

Hydroxide ions, this is what makes them alkaline

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13
Q

What is in a stronger alkali solution

A

Contains more hydroxide ions

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14
Q

What is in a weaker alkali solution

A

It contains less hydroxide ions

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15
Q

What does the higher concentration of hydroxide ions mean

A

That the pH is higher

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16
Q

How can you tell if a solution is weak or strong??

A

Measure their conductivity

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17
Q

A strong acid will show…

A

High conductivity and low pH

18
Q

A weak acid will

A

Not conduct well and has a higher pH

19
Q

A strong alkali will show

A

High conductivity and high pH

20
Q

A weak acid will

A

Show low conductivity and low pH

21
Q

What happens when an acid reacts will a metal

A

Hydrogen is displaced, leaving a salt in solution. It’s a redox reaction.

22
Q

What are bases

A

Bases are a group of compound that reacts with acid, and neutralises them, giving a salt and water. Bases include alkalis, and insoluble metal oxides, hydroxides an carbonates.

23
Q

Bases with alkalis

A

Acid + alkali –> salt + water

24
Q

Bases with metal oxides

A

Acid + metal oxide —> salt + water

25
Q

Bases with carbonates

A

Acid + metal carbonates —> salt + water + carbon dioxide.

26
Q

Reactions of bases

A

Neutralising acids, giving salt and water. With carbonates carbon dioxide is produce too.

All the alkalis (except ammonia) will react with ammonium compounds, giving ammonia out

27
Q

What is an ionic equation

A

An equation that shows only the ions that actually take part in the reaction. It leaves out the rest.

  1. First write down all the ions present in the equation
  2. now cross out any ions that appear, unchanged, on both sides of the equation.
  3. What’s left is the ionic equation for the reaction.
28
Q

Proton donors and acceptors

A

Acids donate its protons to bases and bases except them.

For example:
Magnesium oxide is a insoluble base. The acid donates its H+ protons and the oxygen from magnesium oxide react with it to make water molecules.

29
Q

Why do crops grow best when the pH of the soil is 7

A

If the soil is too acidic or too alkaline, crops grow badly or not at all

30
Q

Why the soil being too acidic is usually the problem?

A

Because a lot of vegetation rotting in it or because too much fertiliser was used in the past.

31
Q

How can you reduce the acidity?

A

The soil is treated with a base like limestone or quicklime or slaked lime

32
Q

How is acid rain caused?

A

Is caused by factories, Power stations, homes who burn fossil fuels to make electricity. The waste gases from all these reactions include Sulphur dioxide, and oxides of nitrogen.they go into the air and react with air and water to produce so sulphuric acid and nitric acid which are strong acids

33
Q

How can you make salts

A

By reacting metals ,insoluble bases or soluble bases with acids.

34
Q

How to make salts with metals

A

1.add the zinc to the sulphuric acid in a beaker.
It will start to dissolve and hydrogen bubbles are given off. Stops when acid is used up.

  1. excess zinc is removed by filtering. This Leaves a aqueous solution of zinc sulphate.
  2. The solution is heated to evaporate some water . Then it is left to cool and crystals of zinc sulphate will start to form.
35
Q

How to make salts with an insoluble base

A

It’s the same as the metal method but the metal will not react with the acid. So you must start with metal oxide

36
Q

How to make salts won an alkali (soluble base)

A
  1. Put the alkali into a flask and add some drops of indicator
  2. add the acid fro, a burette, just a little bit at a time. Swirl the flask in o help the acid and the alkali mix .
  3. when the indicator turns green, stop adding acid.
  4. Calculate how much acid was used.
  5. Carry out the experiment again without the indicator and add the same amount of acid that was used before. They s is because the indicator will make the salt impure.
  6. Heat the solution from the flask and crystals will start to form.
37
Q

What is the process that can help make insoluble salts

A

Precipitation

38
Q

What salts are soluble

A 
Sodium 
Potassium 
Ammonium 
All nitrates 
Chlorides 
Sulphates 
Sodium, potassium and ammonium carbonates
39
Q

What salts are insoluble

A

Silver and lead chloride
Calcium barium and lead sulphate
All carbonates except sodium , potassium and ammonium

40
Q

Preparing a barium sulphate

A

Barium sulphate is a soluble salt. You can make it b mixing solutions of barium chloride and magnesium sulphate

  1. make up solutions of barium chloride and magnesium sulphate
  2. Mix them. A white precipitate of barium sulphate forms at once
  3. filter the mixture. The precipitate is trapped in the filter paper
  4. Rinse the precipitate by running distilled water through it
  5. Then place it in a warm oven to dry
41
Q

How do you precipitate an insoluble salt

A

Must mix the solution that contains its positive ions with one that contains its negative ions

Chemistry (32 decks)

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