Acids, alkalis and salts

Question 1

What colour is phenolphthalein when acidic?

Answer 1

colourless

Question 2

What colour is phenolphthalein when alkali?

Answer 2

pink

Question 3

What colour is methyl orange when acidic?

Answer 3

red

Question 4

What colour is methyl orange when alkali?

Answer 4

yellow

Question 5

What colour is litmus paper when acidic?

Answer 5

red

Question 6

What colour is litmus paper when neutral?

Answer 6

purple

Question 7

What colour is litmus paper when alkali?

Answer 7

blue

Question 8

What is the pH scale range?

Answer 8

0-14

Question 9

What range is classed as strongly acidic?

Answer 9

0-3

Question 10

What range is classed as weakly acidic?

Answer 10

4-6

Question 11

What pH number is classed as neutral?

Answer 11

7

Question 12

What range is classed as weakly alkali?

Answer 12

8-10

Question 13

What range is classed as strongly alkali?

Answer 13

11-14

Question 14

what are the two forms of universal indicator?

Answer 14

• solution in ethanol

- pH paper

Question 15

How to use pH paper with a gas

Answer 15

• damp paper first

- then put in gas

Question 16

How to use pH paper with a solution

Answer 16

• one drop of solution placed on pH paper

Question 17

What is an acid?

Answer 17

proton donor - source of H+ ions

Question 18

What is a base?

Answer 18

proton acceptor - source of OH- ions

Question 19

acid + metal ➡

Answer 19

salt + hydrogen

Question 20

acid + metal oxide➡

Answer 20

salt + water

Question 21

acid + metal hydroxide➡

Answer 21

salt + water

Question 22

acid + metal carbonate ➡

Answer 22

salt + water + carbon dioxide

Question 23

Which common salts are all soluble?

Answer 23

• sodium salts
• potassium salts
• ammonium salts
• nitrates

Question 24

which chloride is not soluble?

Answer 24

silver chloride

Question 25

which sulfates are not soluble?

Answer 25

barium and calcium

Question 26

apart from ammonium, potassium and sodium, common carbonates are ..

Answer 26

insoluble

Question 27

Describe how to prepare soluble salts using excess method (except potassium and sodium)

Answer 27

• heat dilute acid in beaker using bunsen burner (making sure acid doesn’t boil)
• add insoluble base at a time until in excess
• filter mixture to get a pure solution into evaporating dish
• leave filtrate in warm place for water to evaporate and crystals form
• remove crystals and dry them with filter paper

Question 28

How do you know when a base is in excess?

Answer 28

• suspension of the base forms in acid

Question 29

what is a titration?

Answer 29

• a method of determining the exact volume of solution needed to react with a given volume of another solution

Question 30

describe how to carry out an acid-alkali titration

Answer 30

• put 25cm3 of alkali solution in conical flask using volumetric pipette
• add few drops of indicator
• put acid into burette and note initial reading
• add acid to alkali until indicator just changes colour
• note final reading and subtract initial readaing to find exact volume
• repeat without indicator