C8. Acids, bases and salts Flashcards Preview

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Flashcards in C8. Acids, bases and salts Deck (28)
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1

What is the pH scale range for acids?

1 - 6

2

What is the pH scale for neutral?

7

3

What is the pH scale for bases?

8 - 14

4

What are 'acids'?

A compound which produces hydrogen ions when dissolved in water.

5

Name the reactions of dilute acids.

- Metal + acid -> salt + hydrogen
- Metal pxides + acid -> salt + water
- Carbonates + acid -> salt + water + carbon dioxide

6

What is a 'base'?

A substance that can neutralise an acid.

7

What is an 'alkali'?

A soluble base.

8

Name the reactions of bases with acids.

- Base + acid -> salt + water

9

What are 'oxides'?

Compounds of metals or non-metals with oxygen.

10

How are acidic oxides formed?

Non-metals reacting with oxygen.

11

How are basic oxides formed?

Metals reacting with oxygen.

12

How do we make salts?

- Reacting a metal with an acid
- Reacting an insoluble base with an acid
- Neutralising an alkali with an acid by the titration method
- By precipitation

13

What are the conditions for making salts from metals?

Only for metals above hydrogen in the reactivity series.

14

How do we make salts from metals?

- Add the metal to the acid in a flask so that the metal is in excess.
- Warm the flask gently to complete the reaction.
- Filter off the excess metal.
- Put the filtrate into an evaporating basin and evaporate the water until the crystallisation point is reached; allow salt to crystallise at room temp.
- Filter off the crystals and wash them with a tiny amount of solvent so they don't dissolve.
- Dry the crystals between sheets of filter paper.

15

How to make salts from insoluble bases?

By reacting an insoluble base with an acid.
Only for metals that are low in the reactivity series.

16

How to test for hydrogen?

Lighted splint at the mouth of the test tube -> squeaky pop

17

How to test for oxygen?

Glowing splint into the test tube -> splint relights

18

How to test for ammonia?

Holds a damp red litmus paper at the mouth of the test tube -> turns red litmus blue

19

How to test for carbon dioxide?

Limewater -> turns cloudy/milky

20

How to test for chlorine?

Damp litmus paper at the mouth of the test tube -> paper turns white - bleached

21

How to test for sulfur dioxide?

Potassium mangante(VII), which is purple -> turns the liquid colourless

22

Tests for cations by means for aqueous sodium hydroxide:
- ammonium
- copper(II)
- iron(II)
- iron(III)
- zinc

Ammonium: white precipitate
Copper: light blue precipitate
Iron(II): grey-green precipitate
Iron(III): reddish-brown precipitate
Zinc: white precipitate

23

Tests for cations by means for aqueous ammonia:
- ammonium
- copper(II)
- iron(II)
- iron(III)
- zinc

Ammonium: white precipitate
Copper: light blue precipitate
Iron(II): grey-green precipitate
Iron(III): reddish-brown precipitate
Zinc: white precipitate

24

How to identify carbonates?

Adding a dilute acid to an unknown compound then testing the gas produced with limewater.

25

How to identify halides/chloride?

Aqueous silver nitrate under acidic conditions.

26

How to identify nitrates?

Adding sodium hydroxide and aluminium foil, warming gently, then test for the release of ammonia gas.

27

How to identify sulfates?

Adding acidified barium chloride to the unknown compound -> white precipitate

28

How to identify sulfites?

Adding dilute hydrochloric acid, warming and testing for sulfur dioxide.