This apparatus is used to prepare a soluble salt from an acid and an alkali. Fig. 1 shows sulfuric acid in a conical flask and potassium hydroxide in a bure...
Question 1 Report
This apparatus is used to prepare a soluble salt from an acid and an alkali. Fig. 1 shows sulfuric acid in a conical flask and potassium hydroxide in a burette. The student first carries out a titration using indicator. The student then repeats the procedure using exactly the measured volumes but without indicator, so pure potassium sulfate solution can be crystallised.
(a) Give the name of the salt produced. [1]
(b) Use the method to describe why indicator is not added during the final preparation. [1]
(c) Describe two steps needed after neutralisation to obtain dry salt crystals from the solution. [2]
Fig. 1 shows a student comparing the electrical conductivity of dilute hydrochloric acid, ethanoic acid and distilled water. Equal volumes are placed in separate beakers. The circuit includes a lamp and two graphite electrodes. The hydrochloric acid makes the lamp brightest. The student uses the same battery and cleans the electrodes between liquids.
(a) Give the acid that makes the lamp brightest. [1]
(b) Describe what the bright lamp shows about this acid solution. [1]
(c) Use ions to give why distilled water gives little or no light. [2]
Answer Details
Preparation of potassium sulfate
(a) Sulfuric acid reacting with potassium hydroxide produces potassium sulfate. [1]
(b) Indicator is omitted in the final preparation because it would contaminate the salt solution and the crystals. [1]
(c) Heat the neutral salt solution to evaporate some water and make it concentrated. Then cool it to crystallise the salt, and filter and dry the crystals. [2]
Electrical conductivity investigation
(a) Hydrochloric acid makes the lamp brightest. [1]
(b) A bright lamp shows that the hydrochloric acid solution conducts electricity well. [1]
(c) Distilled water contains very few, or no, mobile ions. Without mobile ions to carry charge through the liquid, there is little or no current and therefore little or no light. [2]
Download The App On Google Playstore
Everything you need to excel in your exams
