PLEASE HELPPPP AS chemistry practical.....!!

[hell0]

Ok so I have the practical - paper 3 on nov 3.
And for the second part of the question.. about the testing things.
I DON'T UNDERSTAND HOW YOU TEST FOR GASES....!!!
what if yu do a test, gas is released and you have to test for it but the gas is already gone?
And some of them take too long! and you only one chance.
Will they provide with all the materials for every single gas test?
and most important! how do you know which gas is released!!? if you don't know one of the reactants

[Deadly_king]

Ok so I have the practical - paper 3 on nov 3.
And for the second part of the question.. about the testing things.
I DON'T UNDERSTAND HOW YOU TEST FOR GASES....!!!
what if yu do a test, gas is released and you have to test for it but the gas is already gone?
And some of them take too long! and you only one chance.
Will they provide with all the materials for every single gas test?
and most important! how do you know which gas is released!!? if you don't know one of the reactants

Testing for a gas usually requires some form of heating before the gas evolves. Hence before heating you need to have all the necessary materials ready. Moreover you should have a hint which gas is going to be liberated upon the experiment you are carrying out.

Example :
1.You must already have a damp litmus paper(red or blue) at the mouth of your boiling tube if you are testing for chlorine gas.

Try this, it might be helpful :
http://www.practicalchemistry.org/experiments/advanced/category.html

Let me know if you still have some doubts

[Vin]

Yup. Get all your things in one place. You might even have to repeat the experiment a couple of times. Remember never to touch the litmus paper to the test tube. Don't be satisfied with the results you get, even if you have a slightest doubt what gas is liberated, test it again to be sure. Also, don't waste your time repeating it many times except the necessary requirement.

Good Luck!

[hell0]

Ok, so for example what if it tells you to add HCL to FA1 and observe changes and test for the gas?
What gas would that be?

[Vin]

Yeah, you should guess that you have to test for Cl₂ gas. In addition you should be ready for the CO₂ test as well, recollect that addition of dilute acid is the test for CO₃^-, where CO2 is produced.

[Dania]

What is the best reagent to use when asked to distinguish between Pb²⁺and Al³⁺ ions?

[Deadly_king]

What is the best reagent to use when asked to distinguish between Pb²⁺and Al³⁺ ions?

Sulfuric acid.

Pb²⁺ will form a white precipitate of lead(II) sulfate while no visible change occurs with Al³⁺

[Dania]

Thanks