GATE-2018 (24) :Wyllie – Time average equation

CSIR-NET 2015

139. In a productive Ocean surface water pH is 8.3 and deep water pH is 7.8 , What is the surface : deep H+ ion activity ratio?

A) 8.3 : 7.8            B) √ 10:1                       C) 1: √ 10                           D)7.8:8.3

Solution:

Hydrogen Ion concentration and P^H

P^H = -log (H⁺) ------------------(1)

(H⁺) = 10^-7 , which we call a P^H of 7

This means, for example, that a hydrogen-ion concentration of a solution with a P^H of 4 is 10^-4 is 10^-4 mol/l, meaning it contains 0.0001 mol of hydrogen ions in a solution of 1 liter.

P^H = 8.3 , hydrogen ion concentration 10^-8.3 mol/l (surface water)

P^H = 7.8 , hydrogen ion concentration 10^-7.8 mol /l ( deep water)

Therefore, surface : deep H⁺ ion activity = 10^-8.3 / 10^-7.8

= 10^{-8.3 +7.8}

= 10^-0.5

= 1/√10

Surface: deep H⁺ ion activity = 1: √10

Solution:

 

Explanation:

Hydrogen Ion concentration and pH:-

pH is determined by hydrogen-ion concentration.

so, pH is defined by the following formula :- pH=-log(H+)

The concentration of hydrogen ions in any solution we are likely to 

encounter will range from 1 mol to 0.000001 mol per liter of  

solution.

In the case of a neutral solution,

(H+) =10^-7, which we call a pH of 7.

This means, for example, that a hydrogen-ion concentration of a  

solution with a pH of 4 is 10^-4 mol/l , meaning it contains 0.0001 

 mol of hydrogen ions in a solution of 1 liter. In the same way, a 

solution with a pH of 5 contains 10^-5 mol/l of hydrogen ions, a 

solution with pH of 6 contains 10^-6 mol/l of hydrogen ions, while 

the solution with a pH of 7 contains 10^-7 mol/l of hydrogen ions. 

You will notice that if you compare solution with pH of 4 and pH 

of 7 , the difference in pH is only 3, but the concentration of 

hydrogen ions with a pH of 7 is 1000 times as high as with a pH of 

4.

The character of acidic, basic and neutral is defined by the 

concentration of hydrogen ions [H+](mol/L). A solution with a 

concentration of hydrogen ions higher than 10-7mol/L is acidic, 

and a solution with a lower concentration is alkaline (another way 

to say basic). Using the formula, pH=-log[H+], a pH of 7 is neutral, 

a pH less than 7 is acidic, and a pH greater than 7 is basic. As one 

can see from this formula, ten times a given concentration of 

hydrogen ions means one unit lower in terms of pH value (higher 

acidity), and vice versa. 

Pure water is neutral, with a pH of 7.0. When chemicals are mixed 

with water, the mixture can become either acidic or basic. Vinegar 

and lemon juice are acidic substances, while laundry detergents and 

ammonia are basic. 

Chemicals that are very basic or very acidic are called "reactive." 

These chemicals can cause severe burns. Automobile battery acid 

is an acidic chemical that is reactive. Automobile batteries contain 

a stronger form of some of the same acid that is in acid rain. 

Household drain cleaners often contain lye, a very alkaline 

chemical that is reactive.