Chapter 8 Key Concepts

Question 1

What happens when alkali solution becomes saturated?

Answer 1

Any further metal and hydroxide ions form a solid ppt

Question 2

How to show the trend of increasing alkalinity down the group?

Answer 2

• add a spatula of each group two oxide to water in a test tube
• shake mixture. Rn there’s not enuf water to dissolve all of the metal hydroxide that forms. Hence you’ll have a saturated solution of each metal hydroxide with some white solid undissolved at the bottom
• measure pH of each solution
• alkalinity of solution would increase

Question 3

Use of CaOH2

Answer 3

Agriculture

• added to fields as white lime powder by farmers to increase pH of acidic soil
• neutralises soil to make water

Eg CaOH2 + 2H+ -> 2H2O + Ca2+

Question 4

Uses of MgOH2

Answer 4

Milk of magnesia. A suspension of white MgOH2.

MgOH2s + 2HCl aq-> MgCl2aq + 2H20l

Question 5

Uses of Mg and CaCO3

Answer 5

The main ingredients of indigestion tablets acting as antacids.
CaCO3+2HCl -> CaCl2 + H20 + CO2

Question 6

Trend down in bp group 7

Answer 6

More e
Stronger lf
More energy needed to break intermolecular forces
Bp increases

Question 7

Trend in reactivity of group 2

Answer 7

Atomic radius increases
Outer shell electrons experience more shielding
Less nuclear attraction to outermost electrons
Reactivity decreases

Question 8

Trend in reactivity of group 2

Answer 8

Atomic radius increases
Outer shell electrons experience more shielding
Less nuclear attraction to outermost electrons
Reactivity decreases

Question 9

What happens when you add indicator solution to a solution of chlorine in water

Answer 9

Indicator first turns red because two Acids present

Colour the disappears cuz of bleaching action of HClO

Question 10

Pros of using chlorine

Answer 10

Ensures that water is fit to drink
Kills bacteria

*pro out weighs cons
Quality of drinking water would be compromised by diseases eg typhoid and cholera break outs

Question 11

Cons of using chlorine

Answer 11

Extremely toxic gas
Respiratory irritant in small concentrations. Large con can be fatal
Cl in drinking water can react with organic hydrocarbons eg methane from decaying vegetation to make suspected carcinogens aka chlorinated hydrocarbons

Question 12

Use of chlorine tablets

Answer 12

Post natural disasters
Chlorine tablets produce chlorine in low Con at steady rates
-use
Purify water for drinking
Swimming pools
Purify water supply after a natural disaster