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Five solutions A,B,C,D and E when tested with universal indicator showed pH as
4,1,11,7 and 9, respectively. Which solution is
(a) neutral?
(b) strongly alkaline?
(c) strongly acidic?
(d) weakly acidic?
(e) weakly alkaline?
Arrange the pH in increasing order of hydrogen-ion concentration.
Answer:
We know that,
pH of a neutral solution = 7
pH of an acidic solution < 7
pH of a basic solution > 7
The lower the pH of a solution is than 7, the more is it’s acid concentration
The higher the pH of a solution is than 7, the more is it’s base concentration.
Given pH of the solutions
A - 4
B - 1
C - 11
D - 7
E - 9
Arranging in decreasing level of pH (and hence increasing level of H + ion concentration. Because, more the pH, higher the acidic nature, higher the H + ions concentration)
C>E>D>A>B
(from most basic to most acidic)
(a) neutral
pH of D = 7
Hence, it is neutral
(b) strongly alkaline?
pH of C = 11 >> 7
It is much higher than 7, hence it’s strongly alkaline
(c) strongly acidic?
pH of B = 1 << 7
It is much lesser than 7, hence it’s strongly acidic
(d) weakly acidic?
pH of A =4 < 7
It is less than 7, hence its acidic but it is much lesser than 7 , hence it’s weakly acidic.
(e) weakly alkaline?
pH of E = 9 >7
It is more than 7, hence its basic but It is not much higher than 7, hence it’s weakly basic.
