13.2 To use the standard solution of sodium carbonate solution prepared in experiment 13.1 to standardise a given hydrochloric acid solution Flashcards
Why is it not recommended procedure to pipette directly from the volumetric flask?
This is not recommended because any impurities on the pipette would contaminate the entire solution in the volumetric flask.
Why is it important not to add too much indicator?
Indicators are either weak acids or weak bases and adding too much indicator could affect the accuracy of the result. Also, adding too much indicator could give a very intense colour that may make it difficult to see the colour change at the end point.
Why do we have to standardise HCl solution?
The HCl solution must be standardised because HCl itself is not a primary standard, i.e. it is not possible to take an accurately known amount of HCl and dissolve it in a fixed volume of water togive a solution of known concentration.
What is the purpose of carrying out the titration more than once?
Carrying out the titration more than once gives a more accurate titration figure since the average of two readings agreeing to within 0.1 cm3 is used in the calculations.
Describe the appearance of the isolated sodium chloride.
Sodium chloride is a white crystalline solid.
Why is the result of the first titration usually ignored?
It is ignored because it is likely to be inaccurate, since the purpose of the first titration is to tell youapproximately where the end point lies.
Name the gas given off during the titration.
Carbon dioxide. (Na2CO3 + 2HCl —> 2NaCl + H2O + CO2)
