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Chemistry > Topic 3 - Chemical Changes > Flashcards

Topic 3 - Chemical Changes Flashcards

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1
Q

What ions does an acid form in water.
What happens to the ions as the ph decreases ?

A

-An acid forms H+ ions in water.

  • the concentration of H+ ions increases as the ph decreases
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2
Q

What is a base?

A

A base is a substance that reacts with an acid to produce salt and water.

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3
Q

What is an alkali?
What ions does an alkali form in water?

A

-An alkali is a base that is soluble in water. Ph of more than 7

  • an alkali forms OH- ions in water. The higher the pH the more concentration of OH- ions there is.
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4
Q

What are the 3 types of indicators?

A

-litmus

-methyl orange

-phenolthalein

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5
Q

What colour does litmus go in acid, neutral and alkaline.

A

Litmus goes red in acid. Purple in neutral. Blue in alkaline solutions

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6
Q

What colour does methyl orange go in acidic, neutral , alkaline solutions.

A

Methyl orange goes red in acidic, yellow in neutral and alkaline solutions.

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7
Q

What colour does phenolphthalein go in acidic, neutral and alkaline solutions?

A

Phenolphthalein is colourless in acidic or neutral solutions. Pink in alkaline solutions

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8
Q

What’s the reaction between an acid and a base called?
What does it produce?

A
  • neutralisation.

-salt and water

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9
Q

Why is something at pH 7 neutral?

A

Because the concentration of hydrogen ions is equal to the concentration of hydroxide ions

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10
Q

Definition of a strong acid …
Example….

A
  • a strong acid ionises almost completely in water. Acid molecules dissociate to release H+ ions

-hydrochloric acid, sulfuric acid, nitric acid

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11
Q

Definition of a weak acid.
Example…

A

-weak acids do not fully ionise in solutions. Only a small portion of acid molecules dissociate to release H+ ions.

-ethanoic, citric, carbonic acids

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12
Q

Is the ionisation of a weak acid reversible?

A

The ionisation of a weak acid is a reversible reaction.

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13
Q

What is the concentration of an acid?

A

It’s how much there is of it in water. How watered down it is.

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14
Q

What happens to the pH if the concentration of H+ ions increases by a factor of 10?

A

When the concentration of H+ ions increases by a factor of 10, the pH decreases by 1

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15
Q

Acid + metal —-> …..

A

Acid + metal ——> salt + hydrogen

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16
Q

How to test for hydrogen?

A

1) you can test for hydrogen by using a lit splint

2)hydrogen makes a ‘squeaky pop’ with a lit splint

3)the noises comes from hydrogen reacting with oxygen in the air to form water.

17
Q

Acid + metal carbonate —->……

A

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

18
Q

How to test if a gas is carbon dioxide ?

A

You can test if a gas is carbon dioxide by bubbling it through limewater. If the gas is carbon dioxide the limewater will turn cloudy

19
Q

How to test if a gas is carbon dioxide ?

A

You can test if a gas is carbon dioxide by bubbling it through limewater. If the gas is carbon dioxide the limewater will turn cloudy

20
Q

When do salts form?

A

Acid + metal hydroxide/oxide ——> salt + water

Acid +metal —> salt + hydrogen

21
Q

When do salts form?

A

Acid + metal hydroxide/oxide ——> salt + water

Acid +metal —> salt + hydrogen

22
Q

How to carry out the practical to investigate the neutralisation reaction between calcium oxide (base) and dilute hydrochloric acid.

A

1) measure out dilute hydrochloric acid into a conical flask. Then measure out calcium oxide. Add it to the hydrochloric acid.

2)wait for the base to react then measure the ph with universal indicator or a ph probe.

3)repeat this until all the acid has reacted, you’ll know this when you have unreacted base sitting at the bottom of the flask.

23
Q

What are the insoluble salts?

A

Carbonates and hydroxides ,except sodium, potassium and ammonium ones

24
Q

Method of making a soluble salt

A

1)Heat the acid in a water bath to speed up the reaction.

2)then add the base to the acid , they will react to produce a soluble salt . You will know when the base is in excess because all the excess solid will sink to the bottom.

3)filter of the excess solid

4)heat the solution slowly to evaporate some of the water

5)leave the solution to dry and crystals to form

25
Q

What does the acronym OILRIG stand for

A

Oxidation is loss reduction is gain

26
Q

What is oxidation in electrolysis
What’s reduction

A

Oxidation is the loss of electrons
Reduction is the gain of electrons

27
Q

Is the anode positive or negative

A

The anode is the positive electrode.
The cathode is the negative electrode

28
Q

Where do the negative ions (aniodes) go?
Where do the positive ions (cations) go?

A

The negative ions (anions) go to the anode.
The positive ions (cations) go to the cathode

29
Q

Why are the negative ions (anions) oxidised at the anode?

A

Because they are negative ions this means they have more electrons than protons. At the anode they loose electons to become atoms or molecules.

It’s the opposite for cations, they gain electrons at the cathode

30
Q

How to set up a half equation to show electrons being transfered in electrolysis ?

A

1)Put one of the things being oxidised or reduced on one side of the arrow. And the thing it gets oxidised or reduced to on the other side.

2)add electrons (e-) to balance the charges

31
Q

What’s the half equation for sodium losing an electron to become a sodium ion?

A

Na —> Na+ + e-

32
Q

Why can a molten ionic compound be electrolysed but an ionic solid can’t be?

A

Because the ions can move freely and conduct electricity

33
Q

Why is electrolysis of an aqueous solution differnt to a molten ionic compound?

A

Because in an aqueous solution there are hydrogen ions (H+) and hydroxide ions (OH-)

34
Q

What will happen at the cathode if the metal is more reaction than hydrogen ? In an aqueous solution…

A

At the cathode of an aqueous solution, if the metal is more reactive than hydrogen, than hydrogen gas will be produced

35
Q

What will happen at the cathode of an aqueous solution if the metal is less reactive than hydrogen?

A

If the metal is less reactive than hydrogen a solid layer of the metal will be produced

36
Q

What will be formed at the anode of an aqueous solution?

A

Either oxygen, or if a halogen is present that will be formed. Eg: chloride - chlorine.

37
Q

What group of the periodic table do halogens occupy?
Example of one…

A

Group 7
Chlorine

Chemistry (3 decks)

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