Chapter 4

Question 1

What is a strong acid?

Answer 1

Completely dissociates in aqueous solution and released all its hydrogen atoms into solution as H+ ions.

Question 2

What is a weak acid?

Answer 2

Only releases a small proportion of its H+ ions and partially dissociates in aqueous solution.

Question 3

Example of strong acid?

Answer 3

HCL

Question 4

Example of weak acid?

Answer 4

ethanoic acid (CH3COOH)

Question 5

What is a base?

Answer 5

A base neutralises an acid to form a salt.

Question 6

What is an alkali?

Answer 6

A base that dissolves in water and releases hydroxide ions into the solution.

Question 7

Example of a base?

Answer 7

NH3

most metal oxides/hydroxides/ metal carbonates too

Question 8

Example of an alkali?

Answer 8

NaOH

Question 9

What is produced when an acid is neutralised by a metal oxide/hydroxide?

Answer 9

Salt and water only

eg. CuO + H2SO4 —> CuSO4 + H2O

Question 10

What is produced when an acid is neutralised by an alkali?

Answer 10

acid + alkali = salt + water

H+ + OH- –> H2O

Question 11

What is produced when an acid is neutralised by a metal carbonate?

Answer 11

metal oxide + carbonate = salt + water + CO2

ZnCO3 + H2SO4 —> ZnSO4 + H2O + CO2

Question 12

What is a titration?

Answer 12

A technique used to accurately measure the volume of one solution that reacts exactly with another solution.

Question 13

How do you prepare a standard solution?

Answer 13

1) solid is weighed
2) solid is dissolved in distilled water in a beaker
3) solution is transferred into a volumetric flask and the washings are rinsed into the flask with distilled water.
4) The flask is carefully filled to the graduation line by adding distilled water with a pipette.
5) The bottom of the meniscus has to be touching the mark.
6) The flask is inverted slowly several times.

Question 14

How do you read a value from a burette?

Answer 14

Read the value from the top at the bottom of the meniscus.

Question 15

What is an oxidation number?

Answer 15

The number of electrons involved in bonding to a different element.

Question 16

What is the oxidation number of elements?

Answer 16

always 0

eg. H2/ O2/ Na/ Fe

Question 17

What do the oxidation numbers in a compound add up to?

Answer 17

0

Question 18

Is the sign after or before the oxidation number?

Answer 18

The sign is before.

Question 19

How do we know the value of an elements oxidation number? What are the special cases?

Answer 19

The values are normally an elements charge but there are a few special cases;

1) H in metal hydrides = -1 (CaH2)
2) O in peroxides = -1 (H2O2)
3) O bonded to F = +2 (F2O)

Question 20

What is OIL RIG

Answer 20

Oxidation
Is
Loss of electrons

Reduction
Is
Gain of electrons

Question 21

What happens if an element is oxidised ?

Answer 21

It loses electrons and its oxidation number becomes higher.

Question 22

What happens if an element is reduced ?

Answer 22

It gains electrons and its oxidation number becomes lower.

Question 23

What is a redox reaction?

Answer 23

A reaction that involves reduction and oxidation.

Question 24

What is a reducing agent?

Answer 24

An atom that becomes oxidised itself but causes another atom to gain electrons

Question 25

What is an oxidising agent?

Answer 25

An atom that becomes reduced itself but causes another atom to lose electrons