Q4 of 28 Page 187

The hydroxide ion concentration of a solution is 1.0 x 10 –8M. What is the pH of the solution?

Given:

The hydroxide ion concentration of a solution=[OH-]=1.0 x 10-8M


We know that : -


pOH = - log10 [OH-]


⇒ pOH = - log10[1.0 x 10-8]


⇒ pOH = -[ log101.0 + log1010-8 ]


Now, log101.0 = 0


⇒ pOH = -[0 + (-8) log1010 ]


Now, log1010 = 1


⇒ pOH = -[0-8 ]


⇒ pOH = -[-8]


⇒ pOH = 8


According to relation : -


PH + pOH = 14


⇒ PH = 14 - pOH


⇒ PH = 14 – 8


⇒ PH = 6


Hence, pH of the solution is 6.


More from this chapter

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2

The pH values of certain familiar substances are given below:


Analyse the data in the table and answer the following questions:


i) Which substances are acidic in nature?


ii) Which substances are basic in nature?

 3

Why does the colour of copper sulphate change when an iron nail is kept in it? Justify your answer.

 5

Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid is added to test tube A, while acetic acid is added to test tube B. The amount and concentration taken for both the acids are same. In which test tube does the reaction occur more vigourously and why?

 6

Two acids ‘A’ and ‘B’ were kept in beakers. Acid ‘A’ undergoes partial dissociation in water, whereas acid ‘B’ undergoes complete dissociation in water.

i) Of the two acids ‘A’ and ‘B’ , which is weak acid and which is strong acid?


ii) What is a weak acid?


iii) What is a strong acid?


iv) Give one example each.