2.2 Group 2

Question 1

What is the trend of atomic radius? Why?

Answer 1

Atomic radius increases

Larger number of principal energy levels - more electrons

Question 2

What is the trend of first ionisation energy? Why?

Answer 2

Decreases

Larger atomic radius therefore the outer electron is further away from the nucleus
Electrostatic force of attraction is weaker
The electron is more easily lost

Question 3

What is the general trend of melting points? Why?

Answer 3

Decreases

The charge density decreases which decreases the strength of the metallic bonds

Question 4

What is significant about the melting points of group 2?

Answer 4

Magnesium is an anomaly but we just ignore it

Question 5

What is the general trend of electronegativity of group 2? Why?

Answer 5

Electronegativity decreases down the group

Atomic radius increases
Therefore the bonding pair is further away from the nucleus

Question 6

Is electronegativity relevant for group 2? Why?

Answer 6

No

Group 2 are metals and don’t covalently bond

Question 7

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

Answer 7

Solubility increases down the group

Mg(OH)2 - insoluble (white ppt)
Ca(OH)2 - slightly soluble (white ppt)
Sr(OH)2 - soluble (nvc)
Ba(OH)2 - soluble (nvc)

Question 8

What is the general trend in solubility of group 2 sulfates?

Answer 8

Solubility decreases down the group

MgSO4 - soluble (nvc)
CaSO4- slightly soluble (nvc)
SrSO4 - insoluble (white ppt)
BaSO4 - insoluble (white ppt)

Question 9

What are some uses of Mg(OH)2 - magnesium hydroxide?

Answer 9

Antacids 
Laxatives 
Indigestion relief 
Neutralising acidic waste water
Raising soil pH

Question 10

What is special about Mg(OH)2 that is different from normal hydroxide properties?

Answer 10

Hydroxides are corrosive but

Mg(OH)2 is safe to ingest for humans as it is poorly soluble

Therefore a concentration of OH- isn’t present

Question 11

What are some uses of BaSO4 - Barium sulfate?

Answer 11

Barium meal - contrasting agent in X-rays (good at absorbing them)

It is toxic but safe to ingest as it is insoluble

Question 12

When writing a simple ionic equation what do we use?

Answer 12

Strips down to the ions/molecules we care about ignoring the other stuff

Question 13

What are some factors of group 2 metals reacting with liquid water?

Answer 13

Produces a metal hydroxide and hydrogen gas

Question 14

What are some factors of group 2 metals reacting with gaseous water (steam)?

Answer 14

Produces a metal oxide and hydrogen gas

Steam = over 100 degrees

Question 15

What is the general trend of reactivity of group 2? Why?

Answer 15

Reactivity increases down group 2

The outer two electrons are further from the nucleus (more principal energy levels) therefore are less strongly held and easier to lose (weaker ESF)

Question 16

What do group 2 have as a property?

Answer 16

They are reducing agents

They themselves oxidise

Question 17

How is titanium extracted?

Answer 17

1) TiO2 + 2C + 2Cl -> TiCl4 + 2CO
2) TiCl4 + 2Mg -> Ti + 4MgCl2

Magnesium or sodium can be used
Done at very high temperatures and using an argon atmosphere

Question 18

What are disadvantages to the extraction of titanium?

Answer 18

Expensive due to

High temperatures
Argon atmosphere
Cl made by electrolysis (not cheap)
CO waste has to be managed

Question 19

How do you test for a sulfate ion?

Answer 19

Add HCl
Then added BaCl2

If sulfate ions are present BaSO4 is produced
As BaSO4 is insoluble a white ppt is shown

Question 20

Why is a sample acidified first in the test for sulfate ions?

Answer 20

As carbonate ions also produce a white ppt with BaCl solution

So the acid reacts with CO3 ions to prevent a false positive result