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Thursday, September 6, 2007

Chemistry Questions

Hi. need some help for the following questions.

Q1) What other gases is present inside a chimney besides dust, sulphur dioxide and carbon dioxide? [2 marks]Ans: carbon monoxide, oxides of nitrogen. CORRECT?

Q2) Why must a litmus paper be moist when testing for gases? [1 mark]Ans: So that the gas can dissolve in water to form its H+ or OH- ions that determines its acidic/alkaline property. CORRECT?

Q3) What apparutus is best used to transfer 125cm3 of acid into a beaker? [1 mark]Ans: Pipette or burrete?

Q4) Why can't a solution of copper (ii) oxide crystal be heated? Why must it be left evaporating and not heating? [1 mark]Ans: Because the crystals upon heating will decompose. CORRECT?

4 comments:

Anonymous said...

Answer for question3 is pipette. Cos pipette measures 25cm3 of liquid.
So if you want to measure 125 cm3, just do it 3 times using a pipette! =)

And the rest of the answers are correct! yay.hahaha

lijun(: said...

Q3) What apparutus is best used to transfer 125cm3 of acid into a beaker? [1 mark]Ans: Pipette or burrete?

pipette can only measure up to 25cm3, or at most 50cm3 only. so i don't think it's possible to transfer it by pipette..

alwaysLovely said...

Ans: Pipette. There is 125cm3 pipette to transfer the acid (analyte, etc) into the beaker for acid-base titration.

Helen said...

I would like to ask something about the last question >>> yeah i think it will decompose

but can't the answer also be because it contains water of crystallisation .. and heating can cause it to lose this water .. forming an anhydride?