Titrations and Salt Preparations

Question 1

Describe the method of an acid alkali titration

Answer 1

1. rinse the burette with distilled water and fill the burette with standardised solution (the alkali - NaOH)
2. fill the conical flask with the substance being titrated (acid - HCl)
3. put a few drops of phenolphthalein into the flask of acid. it should stay colourless bc its an acid
4. open the stopcock and slowly add the standardised solution to the flask until the solution indicates a colour change (pink) due to alkali added.
5. measure the amount of standarised solution used from the burette
6. repeat until you reach concordant results (0.2 difference only) and find the average of your results.
7. calculate concentration using formula.

Question 2

Describe the method to produce a pure, dry sample of soluble salt starting from an insoluble reactant

Answer 2

1. starting with insoluble reactant - mix/react with suitable acid to form a soluble salt
2. filtration: put the substance through filter paper to remove excess insoluble starting material
3. crystalisation and evaporation: heat substance to evaporate all water until crystals start to form. then pat dry with a paper towel or leave out to dry

Question 3

Describe the method to produce a pure dry sample of soluble salt from an acid and alkali

Answer 3

1. mix the acid and alkali to produce salt and water
2. crystalisation and evaporation: heat substance to evaporate all water until crystals start to form. then pat dry with a paper towel or leave out to dry

Question 4

Describe the method to produce a pure dry sample of an insoluble salt from 2 soluble reactants

Answer 4

1. mix both soluble starting materials to form an insoluble salt. it is obtained from the precipitate of the solution.
2. wash the precipitate and leave outside to dry

Question 5

Describe the method to produce a pure dry HYDRATED sample of copper (ii) sulfate crystals from copper (ii) oxide

Answer 5

1. dissolve copper (ii) oxide into sulfuric acid to form copper (ii) sulfate solution
2. evaporation and crystalisation: heat substance to evaporate excess water until crystals start to form. then pat dry with a paper towel or leave out to dry

Question 6

Describe the method to prepare a pure dry sample of lead (ii) sulfate

Answer 6

1. mix lead (ii) nitrate solution with sulfuric acid to get the precipitate of lead (ii) sulfate
2. filter the precipitate through filter paper and wash it with distilled water
3. leave outside to dry

Question 7

What is the balanced chemical equation for producing copper (ii) sulfate?

Answer 7

CuO (s) + H2SO4 (aq) -> CuSO4 (aq) + H2O (l)

Question 8

What is the balanced chemical equation for producing lead (ii) sulfate?

Answer 8

Pb(NO3)2 (aq) + H2SO4 (aq) -> PbSO4 (s) + 2HNO3 (aq)