Topic 8.4: Strong and weak acids and bases

Question 1

What is the main difference between strong and weak acids/bases?

Answer 1

Extent of ionization/dissociation

a) Strong fully dissociate in solution (=>)
b) Weak partially dissociate in solution (<=>)

Question 2

Which type of substance produces more OH-/H+ ions at the same concentration?

Answer 2

Strong acids/bases

Question 3

Examples of strong acids (3)

Answer 3

a) HCl
b) H2SO4
c) HNO3

Question 4

Examples of weak acids (4)

Answer 4

a) CH3COOH
b) H2CO3
c) Propanoic acid
d) H3PO4

Question 5

Examples of strong bases (2)

Answer 5

a) Group 1 Hydroxides

d) Ba(OH)2

Question 6

Examples of weak bases (2)

Answer 6

a) NH3 (Ammonia)

b) C2H5NH2

Question 7

Definition of a strong acid

Answer 7

It is a good proton donor and has a weak conjugate base

Question 8

Definition of a strong base

Answer 8

It is a good proton acceptor and has a weak conjugate base

Question 9

Experimental techniques used to determine acid / base strengths

Answer 9

a) Conductivity
b) pH
c) Rates of reaction

Question 10

Hypothesis using conductivity to determine strength of an acid / base

Answer 10

Strong acids and bases will be better conductors than weak acids and bases at the same concentration

Question 11

Explanation of difference in conductivity between strong and weak acids/bases

Answer 11

a) The concentration of H+ will be higher in a strong acid than in a weak acid, and the concentration of OH- will be higher than in a weak base
b) The more ions present, the more conductive a solution.

Question 12

Hypothesis using pH to determine strength of an acid / base

Answer 12

At the same concentration, strong acids have lower pH than weak acids / strong bases have a higher pH than weak bases

Question 13

Explanation of difference in pH between strong and weak acids/bases

Answer 13

a) Because pH is a measure of H+ concentration, the pH scale can be used directly to compare the strengths of acids (provided they are of equal molar concentration).
b) The higher the H+ concentration, the lower the pH value.

Question 14

Hypothesis using rates of reaction to determine strength of an acid / base

Answer 14

Strong acids will react more vigorously with metals/carbonates

Question 15

Explanation of difference in pH between strong and weak acids/bases

Answer 15

a) The reaction of acids depend on the concentration of H+ ions.
b) Reaction rate will be sped up with stronger acids.

Question 16

Difference between strength and concentration

Answer 16

a) How much an acid/base disassociates in aqueous solution

b) Number of moles of acid/base in a certain volume.