Question

How many grams of dry NH4Cl need to be added to 2.50 L of a 0.500 M solution of ammonia, NH3, to prepare a buffer solution that has a pH of 8.74? Kb for ammonia is 1.8*10^-5.

Answer 1

Concepts and reason

Buffer:

A buffer is a chemical solution that contains a weak acid/base mixed with its conjugate base/acid (as in the form of salts). It can resist change when a small amount of a strong acid/base is added to it. The acidic buffer solution is made up of less than and the alkali buffer solution is made up of more than.

Fundamentals

Henderson-Hasselbalch equation is a mathematical expression which can be used to calculate the of buffer solutions.

Concentration of acid and base can be calculated as follows:

Write the Henderson-Hasselbalch equation of basic buffer calculation.

Concentration of acid and base can be calculated as follows:

The reaction for given buffer solution can be written as follows

Given data:

So,

Then of given solution can be calculated as follows

Henderson-Hasselbalch was used for calculating the mass of as given below, the values of were substituted in Henderson-Hasselbalch equation.

Then

Finally

The mole of ammonium chloride was calculated as follows:

The mass of ammonium chloride is calculated as follows:

Ans:

The mass of is.