Objective: Determine the amount of sulphate by the gravimetric method.

Procedure
A) To precipitate BaSO4

I)Pipette 25.0ml of given sulphate solution (Na2SO4) into a 250ml beaker.
ii) Add 50ml of water and 5drops of concentrated HCl
iii) Heat to boiling and, with vigorous sitrring, add dropwise from a measuring cylinder 10ml of 10% BaCl2 solution
iv) Cover the beaker with a watch glass and allow digestion for 20 minutes
v) Test for complete precipitation by adding a afew drops of BaCl2 to the clear supernatant liquid.

Part B) Washing and filtration of Ba2SO4 precipitate
I)Decant the clear supernatant by filtration at the vacuum pump, using a pre weighed crucible.
ii) Wash and swirl the precipitate with about 20ml of warm deionised water.
iii)Use a 'rubber-policeman' to dislodge any particles on the beaker.
iv)Allow to settle
v)Decant the liquid through filter paper
vi)Repeat washing and decanting at least twice.
vii)Discard filtrate

Part C) Drying and weighing of BaSO4 precipitate
I) Dry the crucible in the oven at 150 degree celsius for about 1/2 hour.
ii)Cool the crucible with BaSO4 precipitate in a desiccator for about 10 minutes.
iii) Weigh the crucible when it is cooled down.


Questions

1) Why do you add HCl to the mixture of BaCl2 and NaSO4?
2) What are the factors that favour the formation of BaSO4 crystals?
3) How do you check the purity of BaSO4 crystals formed?
4) How do you improve the purity of BaSO4?
5) Besides, determining the amount of sulphate by the gravimetric method, what other objectives does this experiments poses for students?
6) What is the theory behind using instruments such as crucible, vacuum pump and desiccator?

Care to check for a similar question?

https://www.askmehelpdesk.com/math-sciences/gravimetric-analysis-urgent-362986.html

I've checked tt question before... but my questions differ from it... do u know e answers?

All are there except for the 'purity part'. You should get all the answers you need if you read through the thread carefully. Concerning the apparatus you used, you should know their theory since you make use of them, or you have never used them in a laboratory...

For the purity question, you can rewash and re-filtrate. If you have impurities, I guess you know what that means. And just repeat the purification process like you did to purify.