Strong Acids and Weak Acids

Question 1

what happens to acids in aqueous solutions

Answer 1

acids ionise in aqueous solutions - they produce hydrogen ions, H+
for example:
HCl – H+ + Cl-

Question 2

what happens to strong acids (e.g. sulfuric, hydrochloric and nitric acids) in water

Answer 2

ionise completely in water. All acid particles dissociate to release H+ ions.

Question 3

what happens to weak acids (e.g. ethanoic, citric and carbonic acids)
in solution

Answer 3

do not fully ionise in solution.
only a small proportion of acid particles dissociate to release H+ ions.

Question 4

is the ionisation of a weak acid a reversible reaction. Explain answer

Answer 4

yes it is and it sets up an equilibrium between the undissociated and dissociated acid. Since only only a few of the acid particles release H+, the position of equilibrium lies well to the left

Question 5

what is equilibrium

Answer 5

a state in which the rate of the forward reaction equals the rate of the backward reaction

Question 6

what do the reaction of acids involve

Answer 6

the H+ ions reacting with other substances. if the conc. of H+ ions is higher, the rate of reaction will be faster, so strong acids will be more reactive than weak acids of the same conc.

Question 7

what does the pH of an acid or alkali measure

Answer 7

the conc. of H+ ions in the solution

Question 8

what happens at every decrease of 1 on the pH scale

Answer 8

the conc. of H+ ions increase by a factor of 10

Question 9

what happens at every decrease of 2 on the pH scale

Answer 9

the conc. of H+ ions increases by a factor of 100.

Question 10

what is the rule for this

Answer 10

Factor H+ ion concentration changes by = 10 to the power of - x.

Question 11

what is x

Answer 11

the difference in pH. so if pH falls from 7 to 4 the difference is -3, and the factor the H+ ion concentration has increased by is 10 to the power of -(-3) = 10*3

Question 12

what does acid strength tell you

Answer 12

what proportion of acid molecules ionise in water

Question 13

what does concentration measure

Answer 13

how much acid there is in certain volume of water

Question 14

A student added strong acid to a weakly acidic solution of pH 6. the pH of the new solution was found to be 3 . by how many times did the concentration of the H- increase

Answer 14

3 - 6 = -3
change in conc. of H+ = 10 to the power of -(-3) = 10*3 = 1000
so, the conc. of H+ is 1000 times greater at pH = 3 than at pH = 6