Question

Calculate the concentration of buffer components present in 210.00 mL of a buffer solution that contains 0.300 M NH4Cl and 0.300 M NH3 immediately after the addition of 1.00 mL of 6.00 M HNO3.

Answer 1

Answer:

[NH3] = 0.270M

[NH4Cl] = 0.327M

Explanation:

The HNO3 will react with the weak base, NH3, as follows:

HNO₃ + NH₃ → NH₄⁺ + NO₃⁻

Initial moles of each specie of the buffer:

NH3 = NH4⁺ 0.210L * (0.300mol/L) = 0.063moles

The moles added of HNO3 = Additional moles of NH4Cl and the moles substracted of NH3:

0.001L * (6mol / L) = 0.006 moles.

After the addition:

Moles NH3 = 0.063mol - 0.006mol = 0.057moles

Moles NH4Cl = 0.063mol + 0.006mol = 0.0069moles

And their concentrations are:

[NH3] = 0.057moles / 0.211L = 0.270M

[NH4Cl] = 0.069moles / 0.211L = 0.327M