### Chapter 2: Acids, Bases and Salts

Q
##### Acids,Bases, and Salts

Question:

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.

The pH of the neutral solution should be 7. From the given compound, solution D has pH 7. So, solution D will be neutral.

The pH of an alkaline solution should be between 7 and 14. The strongly alkaline solution should have a pH greater than 9. The pH of the solution C and E is 11 and 9 respectively. This means that solution C is strongly alkaline while solution E is weakly alkaline.

The pH of an acidic solution should be less than 7. The strongly acidic solution should have a pH of less than 4. The pH of solution A and B is 4 and 1 respectively. This means that solution A is weakly acidic while solution B is strongly acidic.

(a) D

(b) C

(c) B

(d) A

(e) E

The pH is defined as a scale which is used to measure the concentration of hydrogen ion present in the solution. The expression of pH is shown below:

$\boldsymbol{\mathbf{}pH=-\log { \left[ { H }^{ + } \right] } }$

The pH of the solution is inversely proportional to the concentration of hydrogen ion. This means that the solution that has low pH, will have the highest concentration of hydrogen ions while the solution that has high pH will have the lowest concentration of hydrogen ions. The pH of solution B is 1 while the pH of solution C is 11. This means that solution B contains the highest concentration of hydrogen ion while solution C contains the lowest concentration of hydrogen ions.

Thus, the correct answer C < E < D < A < B.

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