18.1 Further Aspects of Acids & Bases

Sketch the titration curve when 50 cm³ of 0.1 mol dm^-3 HNO₃ (aq) is titrated against 25 cm³ of 0.1 mol dm^-3 NH₃ (aq).

[4]

Select a suitable indicator for the titration from table 22 of the Data booklet.

[1]

Calculate the pH of 0.1 mol dm^-3 ammonia using section 21 of the Data booklet.

[5]

Deduce, using section 21 of the Data booklet whether the pH of 0.1 mol dm^-3 ethylamine would be higher or lower than 0.1 mol dm^-3 ammonia solution.

[1]

Indicators are solutions of weak acids or bases. Methyl red has the molecular formula C₁₅H₁₅N₂O₂.

Draw the structure of the conjugate base of methyl red.

[1]

What will be seen if a few drops of methyl red are added during a titration of 50 cm³ of 0.1 mol dm^-3 HCl (aq) against 25 cm³ of 0.1 mol dm^-3 NaOH ( aq). 

[1]

The pKa of methyl red is 5.1. Explain how this relates to the acid-base character of methyl red when added to water.

[3]

Using section 21 of the Data booklet, discuss the relationship between the chemical structures and acidity of chloroethanoic acid, dichloroethanoic acid and trichloroethanoic acid.

[3]

This question is about acid buffers.

Explain how you could make a buffer given a supply of the following:

20 cm³ of 0.10 mol dm^-3 chloroethanoic acid

20 cm³ of 0.10 mol dm^-3 potassium hydroxide

[3]

Determine the new concentration of each reactant in the buffer.

20 cm³ of 0.05 mol dm^-3 dichloroethanoic acid was reacted with 10 cm³ of 0.10 mol dm^-3 sodium hydroxide. Suggest, with a reason, a pH value for the resulting solution.