Worksheet on pH and pOH values of solutions





The measure of acidity or basicity of an aqueous solution is called pH. Aqueous solution with pH value less than 7 are called acid and solutions having pH value greater than 7 are called basic.

The measurement of pH value is very important in the field of medicine, biology, chemistry etc.

pOH is used to describe the concentration of hydrogen ion.  pOH is derived from pH value rather than measuring it independently.

Here, you can find some question related to “pH and pOH” and its answers:

Questions:

1. At 25^C, the pH value of solution is 6. The solution is:

(a)    Acidic

(b)   Basic

(c)    Neutral

(d)   Alkaline

 

2. When solid potassium cyanide is added in water, then its:

(a)    pH will decrease

(b)   pH will increase

(c)    Electrical conductivity will not change

(d)   pH will remain the same

 

3. If pH values of A, B, C, and D are 2.5, 9.5, 3.5, and 5.5 respectively, then the weakest acid is:

(a)    B

(b)   A

(c)    C

(d)   D

 

4. The aqueous solution of which of the following salts has the lowest pH value?

(a)    NaClO_3

(b)   NaClO_4

(c)    NaClO_2

(d)   NaClO

 

5. The dissociation constant is highest for:

(a)    C_6H_5OH

(b)   C_6H_5CH_2OH

(c)    CH_3C \equiv CH

(d)   CH_3NH_3+_3Cl^-

 

6. Dimethyl glyoxime gives a red precipitate with Ni^{2+}, which is used for its detection. To get this precipitate readily, the best pH range is:

(a)    < 1

(b)   2 – 3

(c)    9 – 11

(d)   3 – 6

 

7. When rain is accompanied by thunderstorm, the collected rain water will have a pH value:

(a)    Slightly lower than that of rain water without thunderstorm

(b)   Which depends on the amount of dust in air

(c)    Slightly higher than that of rain water without thunderstorm

(d)   Uninfluenced by the occurrence of thunderstorm

 

8. what is the pH of 0.01 M glycine solution? For glycine Ka_1 = 4.5 \times 10^{-3}\hspace{2mm} \text{and} \hspace{2mm}Ka_2 = 1.7 \times 10^{-10} 298 K:

(a)    6.94

(b)   7.06

(c)    5.06

(d)   8.02

 

9. The dissociation constant of an acid HA is 1 \times 10^{-5} . The pH value of 0.1 M solution of the acid will be:

(a)    3

(b)   4

(c)    1

(d)   5

 

10. The pH value of an acid is 5 and its concentration is 1 M. What is the value of Ka for the acid?

(a)    10^{-5}

(b)   10^{-10}

(c)    10^{-7}

(d)   10^{-8}

 

11. The pH of the solution, produced when an aqueous solution of pH 5 is mixed with an equal volume of an aqueous solution of pH 3, is:

(a)    3.3

(b)   4.3

(c)    2.5

(d)   6.3

 

12. The pH of pure water is:

(a)    Pressure independent

(b)   Temperature dependent

(c)    Temperature

(d)   Pressure dependent

 

13. Which one of the following statements is true?

(a)    pH + pOH = 14 for all aqueous solutions

(b)   p^H of 1 \times 10^{-8} MCl is 8

(c)    conjugate base of H_2PO^-_4 is HPO^{2-}_4

(d)   96,500 coulomb of electricity when passed through a CuSO_4 solution deposits 1 gram equivalent of copper at the cathode

 

14. A base dissolved in water, yields a solution with a hydroxyl ion concentration of 0.05 mol L^{-1}. The solution is:

(a)    Acidic

(b)   Neutral

(c)    Basic

(d)   Either (a) or (b)

 

15. Which of the following has pH value of 14

(a)    1 M NaOH

(b)   0.1 M NaOH

(c)    0.1 M H_2SO_4

(d)   1 M HCl

 

16. In which of the following acid-base titrations, pH is greater at equivalence point?

(a)    Hydrochloric acid versus ammonia

(b)   Acetic acid versus ammonia

(c)    Hydrochloric acid versus sodium hydroxide

(d)   Acetic acid versus sodium hydroxide ( )

 

17. The pH value of gastric juice in human stomach is about 1.8 and in small intestine it is about 7.8. If the pKa value of aspirin is 3.5, then the aspirin will be:

(a)    Completely ionized in the small intestine and in the stomach

(b)   Unionized in the small intestine and almost unionized in the stomach

(c)    Ionized in the small intestine and almost unionized in the stomach

(d)   Ionized in the stomach and almost unionized in the small intestine

 

18. Which of the following is not a buffer solution?

(a)    0.05 M KClO_4 + 0.005 M HClO_4

(b)   2 M C_6H_5NH_2 + 2M C_6H_5^+NH_3Br

(c)    0.8 M H_2S + 0.8 M KHS

(d)   3 M H_2CO_3 + 3M KHCO_3

 

19. pH  of an acidic buffer is given by:

(a)    pH = 1/2 pKa + \log \dfrac{[salt]}{[acid]}

 

(b)   pH = pKa + \log \dfrac{[salt]}{[acid]}

 

(c)    pH = pKa- \log \dfrac{[salt]}{[acid]}

 

(d)   pH = 1/2 \log Ka + \log \dfrac{[salt]}{[acid]}

 

20. The pH of a buffer solution, containing 0.2 mole per liter of CH_3COONa and 1.5 mol L^{-1} of CH_3COOH is (Ka for acetic acid is 1.8 \times 10^5):

(a)    3.45

(b)   4.87

(c)    5.48

(d)   9.23

 

21. Which of the following solutions is not buffer?

(a)    Boric acid + borax

(b)   Borax

(c)    Sodium chloride

(d)   Potassium hydroxide

Answers:

1.(a)     2. (b)     3. (a)     4. (b)     5. (a)

6. (c)     7. (a)     8. (b)     9. (a)     10. (b)

11. (a)     12. (b)     13. (a)      14. (c)     15. (a)

16. (d)     17. (c)     18. (a)     19. (b)     20. (b)

21. (c)



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