Question

Standardization of Ammonia Solution

In my practical, it says "standardise the supplied 0.2M NH₃ in 2M NH₄NO₃ solution by titration with the standardized 0.1M HCl supplied. Use the conical flask to do the titration. Titrate 10mL aliquot of ammonia solution containing several drops of a suitable indicator with the acid. Titrate to an endpoint of 0.02mL(+-) on the burette.

Question:

Is the 0.2M NH₃ in 2M NH₄NO₃ solution a single solution? (or 0.2M NH3 have to be mixed with NH4NO3 solution?) And when doing titration, does the ammonia solution have to go on beaker (10mL?) with few drops of indicator and HCl solution on burette? And I am not sure whats it meant by titrating to an endpoint of 0.02mL(+-) on the burette.

Thanks!

Answer 1

0.2M NH3 +2M NH4NO3 is a combination of NH3/NH4⁺ that is conjugate base and its salt combination ,so it is a buffer solution with ka=5.6E-10 and a fixed pH range.It is a single solution ,as only NH3 is neutralized by HCl on titration.

NH3 + HCl--->NH4⁺ +Cl^-

10mL aliquot of ammonia solution containing several drops of a suitable indicator is to be taken in the beaker and HCl will go in the burette.

Titating to an end point with standard admissible error of 0.02 ml: this means if your end point is ,say, 20.5 ml then it can be 0.02ml or in other words 20.5ml0.02ml