topic 4 - reactions and trends

Question 1

Describe the change from metallic to non-metallic character across a period

Answer 1

Electronegativity increases as we move from left to right in a period, Ionization energy decreases, and the tendency to obtain electrons increases, resulting in a decrease in metallic character and an increase in non-metallic character.

Question 2

Physical properties of metals

Answer 2

Metals
Shiny
High melting points
Good conductors of electricity
Good conductors of heat
High density
Malleable and ductile

Question 3

physical properties of non metals

Answer 3

Non metals
dull
low melting points
Poor conductors of electricity
poor conductors of heat
low density
brittle

Question 4

Describe the Group VIII noble gases as unreactive, monatomic gases and explain this in terms of electronic configuration

Answer 4

Noble gases are unreactive because their outer shell are full. This means that they are stable without having to gain or lose electrons.

Question 5

Describe the general chemical properties of metals, limited to their reaction with oxygen

Answer 5

Many metals react with oxygen to form metal oxides. Potassium and sodium are soft metal which are easily cut exposing a shiny surface which changes to dull rapidly. The change from shiny to dull is called tarnishing.

Question 6

oxidation

Answer 6

a process in which an electron is removed from a molecule during a chemical reaction

Question 7

reduction

Answer 7

any of a class of chemical reactions in which the number of electrons associated with an atom or a group of atoms is increased

Question 8

Identify redox reactions as reactions involving gain and loss of oxygen

Answer 8

Chemical reactions in which oxygen and/or hydrogen are transferred are called oxidation-reduction, or redox, reactions. Oxidation is the gain of O or loss of H. Reduction is the loss of O or gain of H.

Question 9

Define redox reactions as involving simultaneous oxidation and reduction

Answer 9

Redox reactions, also referred to as oxidation-reduction processes, are reactions in which electrons are transferred from one species to another.

Question 10

Describe the general chemical properties of metals, limited to their reactions with dilute acids

Answer 10

Most metals react with dilute acids to form a salt solution and hydrogen gas.

Question 11

Identify oxidation and reduction in redox reactions

Answer 11

An increase in oxidation number during a reaction corresponds to oxidation, while a decreases corresponds to reduction.

Question 12

The reactivity series typically includes the following elements:

Answer 12

potassium, sodium, calcium, magnesium, aluminum, zinc, iron, lead, copper, silver and gold

Question 13

Explain the apparent unreactivity of aluminium in terms of its oxide layer

Answer 13

The reason it does not react is that is has already reacted, but the aluminium oxide has formed in a thin, tightly bonded layer that protects the aluminium foil from further attack.

Question 14

Describe the reactions of potassium, sodium and lithium with cold water

Answer 14

All the alkali metals react vigorously with cold water. In each reaction, hydrogen gas is given off and the metal hydroxide is produced.

Question 15

Describe the general chemical properties of metals, limited to their reactions with cold water and steam

Answer 15

Some metals such as zinc and iron, do not react with cold water but they do react with steam.
Such metals will react with steam to form metal oxide and hydrogen gas.

Question 16

State the order of the reactivity series as:

Answer 16

magnesium, aluminium, zinc, iron, hydrogen, copper, silver, gold

Question 17

Describe the Group I alkali metals, lithium, sodium and potassium, as relatively soft metals with general trends down the group, limited to:

Answer 17

(a) decreasing melting point as you go down
(b) increasing density as you go down
(c) increasing reactivity as you go down

Question 18

Explain similarities in the chemical properties of elements in the same group of the Periodic Table in terms of their electronic configuration

Answer 18

they have the same number of electrons in their outer shell.

Question 19

How does a displacement reaction occur?

Answer 19

A displacement reaction occurs when a more reactive element displaces, or pushes out, a less reactive element from a compound that contains the less reactive element.

Question 20

oxidising agent

Answer 20

a substance that oxidises another substance and is itself reduced

normally a non-metal or positive ion. cause oxidation reactions to take place. gains electrons from other atoms or ions (is itself reduced)

Question 21

Reducing agent

Answer 21

a substance that reduces another substance and is itself oxidised

Usually a metal or a negative ion. loses (donates) electrons to another element or ion (reducing the other species)