A student measured the pH values of four solutions A, B, C and D which were found to be 4, 1, 13 and 11 respectively. Which of the following statements are correct about these solutions ?
(a) A is strong acid and B is weak acid
(b) B is strong acid and D is weak base
(c) D is strong base and C is weak base
(d) C is strong base and A is weak acid

(1) (a) and (b)
(2) (b) and (c)
(3) (c) and (d)
(4) (b) and (d)

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Solution

pH scale ranges from 0-14. Acids have a range of 0-6.9 and bases have a range of 7.1-14. Lower the value of pH stronger the acid or higher the value of pH stronger will be the base. So, A and B are acids but pH of B is less than pH of A, so B is a stronger acid than A. C and D are the bases but pH of C is more than D, so C is stronger base than D.

Hence, the correct answer is option 4.

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