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ICSE Class 10 Chemistry Question 3 of 28

Acids, Bases and Salts — Question 16

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Question

Question 16

Define pH value. What would you say about the pH of a solution in which

(i) H+ aq. ions = OH- ions

(ii) evolves CO2 when heated with Na2CO3

(iii) OH-ions > H+ aq. ions.

Answer

pH is defined as the negative logarithm [to the base 10] of the hydrogen ion concentration expressed in moles/litre. Thus, pH = -log10H+. It represents the strength of acids and alkalis, expressed in terms of hydrogen ion concentration [H+ aq.]

(i) When, H+ ions = OH- ions, the solution is neutral with pH = 7.

(ii) When the solution evolves CO2 when heated with Na2CO3, it is acidic in nature with pH less than 7.

(iii) when, OH-ions > H+ aq. ions, the solution is basic in nature with pH more than 7.