Chapter 11.3: Strength and concentration

Question 1

How do strong and weak acids differ?

Answer 1

Strong acids fully ionise in aqueous solution while weak acids only partially ionise

Same concept applies for strong/weak bases

Question 2

Name 2 weak acids

Answer 2

Ethanoic/carbonic

Question 3

Name a weak alkali

Answer 3

Ammonia solution

Question 4

What are the differences between the strength and concentration of an acid?

Answer 4

• Strength refers to extent of ionisation of an acid/base
• Concentration refers to how much of an acid or base is dissolved in a solution

These 2 do not affect each other but both affect the pH of a solution

Question 5

What are some methods to measure pH?

Answer 5

• Indicators
• pH sensors attached to a data logger
• pH meter

Question 6

What are the benefits of a pH meter?

Answer 6

Measures pH electrically, accurately and reliably.

Question 7

Formula for pH

Answer 7

-log(concentration of H+ ion)

Look carefully at number of H+ ions for a particular acid

Question 8

Why do we control the pH of soil?

Answer 8

pH of soil may become unsuitable for plant growth due to:
- too much fertiliser
-environmental pollution (acid rain)

Question 9

How do we control the pH of soil?

Answer 9

• Calcium oxide (quicklime)
• Calcium hydroxide (slaked lime)

Known as “liming”, neutralising the acid in the soil