Random revision - Unit 1

Question 1

What is the activation energy?

Answer 1

The minimum energy required by colliding molecules for a reaction to occur

Question 2

Why is it essential that chemists can predict the quantity of heat taken in or given out in an industrial process?

Answer 2

1. Endothermic reactions require heating which results in high energy costs.
2. Runaway reactions such as those causing the disasters in Bhopal and Seveso occur when the rate at which a chemical reaction releases energy exceeds the capabilities of the plant to remove heat.

Question 3

What is temperature?

Answer 3

A measure of the average kinetic energy of the particles in a chemical

Question 4

Describe the reactivity of group 7

Answer 4

They are reactive. The reactivity decreases down a group.

Question 5

What happens to metallic characteristics across a period

Answer 5

They decrease

Question 6

What is an exception to ‘compounds formed between non metals only, are covalent

Answer 6

Some metals form covalent compounds, e.g. SnI4 and TiCl4

Question 7

What is an exception to “compounds formed between a metal and non mental are ionic”

Answer 7

Acids are also ionic, HCl, H2SO4, HNO3

Question 8

What are Intramolecular forces

Answer 8

The forces that hole atoms together to form a molecule - Polar/Pure covalent bonds

Question 9

WhT are intermolecular forces

Answer 9

The forces of attraction between molecules - Van see Waals forces

Question 10

How do LDFs arise

Answer 10

Temporary uneven distribution of electrons within atoms and molecules

Question 11

The higher the mpt/bpt, the ______ the intermolecular forces

Answer 11

Stronger

Question 12

Why does ice float on water

Answer 12

Ice is less dense because hydrogen bonding between water molecules give ice an open structure. (Molecules of H2O in Ice are further apart) The density of i a is lower than water unlike other chemicals where Solid is more dense than Liquid.

Question 13

What is viscosity

Answer 13

Thickness

Question 14

Why does ionisation energy increase across a period?

Answer 14

The nuclear charge increases as you go across a period. This means that the outer electrons are more strongly attracted to the positive nucleus and are pulled in tighter, requiring more energy to remove them.

Question 15

where do LDFs arise

Answer 15

between all atoms and molecules

Question 16

What is an activated complex

Answer 16

As the reaction proceeds from reactants to products, an unstable intermediate stage is reached at the top of the activation barrier at which a highly energetic species called an activated complex is called

Question 17

Describe covalent molecules

Answer 17

Covalent molecules or compounds have a definite number of atoms bonded tigether

Question 18

Describe covalent networks

Answer 18

Covalent network elements or compounds have a vast but indefinite number or atoms bonded together

Question 19

Explain the change in ionisation energies across a period

Answer 19

As you go across a period the positive charge in the nucleus increases making the atoms smaller. The outer electrons are closer to the nucleus so more strongly attracted. The outer electron is more difficult to remove so the ionisation energy increases.

Question 20

Explain the change in ionisation energies down a group

Answer 20

As you go down a group the atoms are bigger as there is another shell of electrons. The outer electrons are further from the nucleus and are also shielded from the full effect of the nucleus by the inner electrons. The outer electron is easier to remove so the ionisation energy increases.

Question 21

Explain the effect of the electronegativity on electrons in a covalent bond

Answer 21

The higher the electronegativity the stronger the attraction of the atom for the shared electrons in a covalent bond.

Question 22

What is electronegativity

Answer 22

Electronegativity is a chemical property that describes the tendency of an atom or a functional group to attract electrons toward itself