Group 2 and Group 7, Rates, Equilibria and Shapes.

Question 1

Describe the trend in ionisation energy in group 2.

Answer 1

The ionisation energy decreases down the group.

Question 2

Explain the trend in ionisation energy in group 2.

Answer 2

The ionisation energy decreases because the number of electron shells increases down the group, which increases:

• shielding by inner inner shells of electrons
• atomic radius

This makes it easier to remove the outer electron because it has less attraction to the nucleus.

Question 3

What three substances do group 2 elements react with?

Answer 3

Water, oxygen and chlorine.

Question 4

What three substances do group 2 elements react with?

Answer 4

Water, oxygen and chlorine.

Question 5

What type of reaction takes place when group 2 elements react, considering they lose 2 electrons?

Answer 5

Oxidation

Question 6

What is the general change in the oxidation number of group 2 elements when they react?

Answer 6

0 to 2+

Question 7

What is the reaction between a group 2 element and water? (M = group 2 element)

Answer 7

M (s) + H20 (l) —> M(OH)2 (aq) + H2 (g)

A metal hydroxide and hydrogen are formed.

Question 8

What is the trend in reactivity between group 2 elements and water?

Answer 8

The reactivity of group 2 elements increases down the group because their ionisation energies decrease.

Question 9

What is the trend in reactivity between group 2 elements and water?

Answer 9

The reactivity of group 2 elements increases down the group because their ionisation energies decrease.

Question 10

Describe the reactivity of Magnesium with water.

Answer 10

Magnesium reacts VERY SLOWLY with water.

Question 11

Describe the reactivity of Strontium with water.

Answer 11

Reacts FAIRLY QUICKLY

Question 12

Describe the reactivity of Barium with water.

Answer 12

Reacts RAPIDLY

Question 13

Describe the reactivity of Beryllium with water.

Answer 13

Doesn’t react.

Question 14

What is the reaction between a group 2 element and oxygen?

Answer 14

2M(s) + O2 (g) —-> 2MO (s)

A solid white oxide is produced.

Question 15

What is the reaction between group 2 elements and chlorine?

Answer 15

M (s) + Cl2 (g) —> MCl2 (s)

Question 16

The oxides of group 2 metals react readily with water to form _____ ______, which dissolve. The _________ ions make these solutions strongly alkali.

Answer 16

The oxides of group 2 metals react readily with water to form metal hydroxides, which dissolve. The hydroxide ions make these solutions strongly alkali.

Question 17

The oxides of group 2 metals react readily with water to form _____ ______, which dissolve. The _________ ions make these solutions strongly alkali.

Answer 17

The oxides of group 2 metals react readily with water to form metal hydroxides, which dissolve. The hydroxide ions make these solutions strongly alkali.

Question 18

Which group 2 oxide is an exception to the rule that the hydroxides produced when reacted with water are soluble?

Answer 18

Magnesium oxide. Its hydroxide reacts slowly and is not very soluble.

Question 19

What is the trend in the strength of the alkali produced in hydroxides of group 2 elements?

Answer 19

Oxides form stronger alkali solutions as you go down the group.

Question 20

What is the trend in solubility of group 2 hydroxides down the group?

Answer 20

The hydroxides get more soluble down the group.

Question 21

What is the trend in solubility of group 2 hydroxides down the group?

Answer 21

The hydroxides get more soluble down the group.

Question 22

What is the trend in solubility of compounds that contain double charged negative ions? (CO3 2-)

Answer 22

They decrease in solubility down the group.

Question 23

What is the trend in solubility of compounds that contain single charged negative ions? (OH-)

Answer 23

They increase in solubility down the group.

Question 24

Which group 2 sulphate is insoluble?

Answer 24

Barium sulphate

Question 25

Define activation energy.

Answer 25

The minimum amount of (kinetic) energy particles need to react.

Question 26

Which two things allow a reaction to take place between two particles?

Answer 26

1. The direction of collision.

2. The energy that particles collide with.

Question 27

Define a catalyst.

Answer 27

A substance that lowers the activation energy of a reaction by providing an alternate pathway, without being used itself.

Question 28

Why does increasing the temperature increase the rate of a reaction?

Answer 28

• At higher temperatures, particles have a higher average energy and will therefore move faster.
• This means that the frequency of collisions between particles increase.
• It also means that a higher proportion of particles will have an amount of (kinetic) energy equal to or greater than the activation energy, allowing them to react.
• Therefore, a greater percentage of all collisions between particles will be successful.

Question 29

Why can a catalyst increase the rate of reaction?

Answer 29

• A catalyst lowers the activation energy.
• This means that a greater proportion of particles will have the amount of (kinetic) energy equal to or greater than the activation energy.
• Therefore there are a greater proportion of successful collisions between particles.

Question 30

How can we measure the rate of reaction for gases?

Answer 30

A gas syringe can be used to collect gases produced, and the volume evolved can be recorded at regular intervals.

Question 31

How can we measure the rate of reaction for solids?

Answer 31

For reactions that produce precipitates or clouds, the rate can be measured by observing the visibility of a marker through the solution/precipitate. The time taken for the marker to disappear can be recorded for each different concentration/temperature, etc.

Question 32

What are homogeneous catalysts?

Answer 32

They are types of catalysts which are in the same state as the reactants of the reaction that they are catalysing.

Question 33

What do homogeneous catalysts do differently to normal catalysts?

Answer 33

They form intermediaries with the reactants and then the products are formed from the intermediate compounds. This is the alternative pathway.

Question 34

What do homogeneous catalysts do differently to normal catalysts?

Answer 34

They form intermediaries with the reactants and then the products are formed from the intermediate compounds. This is the alternative pathway.

Question 35

What differences will there be on the enthalpy profiles of homogeneously catalysed reactions and normally catalysed reactions?

Answer 35

There will be two bumps/peaks on the homogeneously catalysed reaction, but only one bump/peak on the normally catalysed reaction. This is because the homogeneously catalysed reactions involves the production of intermediates.

Question 36

How can we measure the rate of reaction for gases?

Answer 36

• A gas syringe can be used to collect gases produced, and the volume evolved can be recorded at regular intervals.
• The solution, in a beaker, can be placed on a weighing scale and the mass of the beaker and solution can be recorded at regular intervals. The mass would decrease as gas is produced. (for non-toxic gases)

Question 37

What differences will there be on the enthalpy profiles of homogeneously catalysed reactions and normally catalysed reactions?

Answer 37

There will be two bumps/peaks on the homogeneously catalysed reaction, but only one bump/peak on the normally catalysed reaction. This is because the homogeneously catalysed reactions involves the production of intermediates.

Question 38

Why does increasing the concentration increase the rate of reaction?

Answer 38

• A higher concentration means that particles will be closer to each other.
• If particles are closer to each other, they will collide with each other more often.
• If particles collide more often, the frequency of successful collisions will increase.

Question 39

Why does increasing the surface area increase the rate of reaction?

Answer 39

• A higher surface area means that more particles can come into contact with each other.
• If more particles can come into contact with each other, the frequency of collisions will increase and therefore the frequency of successful collisions will also increase.