Question

A solution is prepared by dissolving 0.23 mol of nitrous acid and 0.27 mol of sodium nitrite in water sufficient to yield 1.00 L of solution. The addition of 0.05 mol of HCl to this buffer solution causes the pH to drop slightly. The pH does not decrease drastically because the HCl reacts with the __________ present in the buffer solution. The Ka of nitrous acid is 1.36 × 10-3.A) H2OB) H3O+C) nitrite ionD) nitrous acidE) This is a buffer solution: the pH does not change upon addition of acid or base.

Answer 1

Complete Question

A solution is prepared by dissolving 0.23 mol of nitrous acid and 0.27 mol of sodium nitrite in water sufficient to yield 1.00 L of solution. The addition of 0.05 mol of HCl to this buffer solution causes the pH to drop slightly. The pH does not decrease drastically because the HCl reacts with the __________ present in the buffer solution. The Ka of nitrous acid is 1.36 × 10-3.

A) H2O

B) H3O+

C) nitrite ion

D) nitrous acid

E) This is a buffer solution: the pH does not change upon addition of acid or base.

Answer:

The correct option is  C

Explanation:

From the question we are told that

           The number of moles of nitrous acid is  $n = 0.23 \ mols$

          The number of moles of sodium nitrite is $m = 0.27 \ moles$

          The volume of the solution is  $V = 1.00\ L$

           The number of mole added is  $z = 0.05 \ moles$

             The Ka for nitrous acid is  $Ka = 1.36 *10^{3}$

Now looking at the question  we can see that the solution is  made up of

     A weak acid , and its salt and a strong base and this would imply that the buffer is an acidic buffer what this mean is that  the  addition of small amount of  acid to the solution would pH

   Sine Nitrite  ion is the basic component of the buffer the it then means that the HCl would react with the Nitrite  

Answer 2

Answer:

C) nitrite ion

Explanation:

From the system as given, it represents acidic buffer, this is by its constituents of a weak acid and it's salt with strong base.

The pH level of buffer solution doesn't have any form of changes upon addition of small amount of acid or alkali as they are consumed by component of buffer.

In this case as given, HCl added would react with Nitrite ion as it is the basic component of buffer.