Question

IN THE FOLLOWING ACID (HNO₃) WHY IS H+ FROM H₂O NEGLIGIBLE AND IN WHICH CASES WOULD IT NOT BE NEGLIGIBLE? WHY WOULD THE H+ IONS FROM HNO₃ NOT BE NEGLIGIBLE? WHY DO THE H+ IONS FROM THE ACID DRIVE THE EQUILIBRIUM TO THE LEFT AND WHY WOULD THE H+ IONS FROM H₂O NOT DRIVE THE EQUILIBRIUM? ALSO, IN WHICH CASE(s) WOULD THE EQUILIBRIUM BE SHIFTED TO THE RIGHT?

Calculate the pH for the following acids:
0.10 M HNO₃

Major species: H+, NO₃^-, and H₂O

The H+ ions from the acid will drive the equilibrium H₂O ( l ) = H⁺ ( aq ) + OH^- to the left.

Sources of H⁺:

1) H⁺from HNO₃ ( 0.10 M )

2. H⁺ from H₂O ( negligible )

[ H+ ] = 0.10

pH = -log ( 0.10 ) = 1.00

IN THE FOLLOWING ACID, (HNO₃), WHY IS H+ FROM H₂O NEGLIGIBLE AND IN WHICH CASES WOULD IT NOT BE NEGLIGIBLE? WHY WOULD THE H+ IONS FROM HNO₃ NOT BE NEGLIGIBLE? WHY DO THE H+ IONS FROM THE ACID DRIVE THE EQUILIBRIUM TO THE LEFT AND WHY WOULD THE H+ IONS FROM H₂O NOT DRIVE THE EQUILIBRIUM? ALSO, IN WHICH CASE(s) WOULD THE EQUILIBRIUM BE SHIFTED TO THE RIGHT?

Answer 1

Water is a very stable compound it dissociates in a very small amount , its dissociation constant is

So H+ and OH- ions we get from water are very low. On the other hand, Nitric acid is a strong acid and it releases H+ ions readily in water ,thats why the number of H+ ions are far more as compared to water . So those from Water can be neglected.

It will not be neglected when we get a very weak acid giving some H+ ions.

Shifting of equilibirium : If the quantity of reactants is increased ,then it will react more and more product will be formed; hence equilibirium is shifted to the right,

While if the products concentration is increased , then the equilibirium will shift to the left .

This is known as Le-Chatelier's principle.