O Level Chemistry & IP Chemistry Notes by 10 Year Series Author - Chemistry Specialist

O Level Chemistry Made Easy

O Level Chemistry Questions: Experimental Techniques / Purification & Separation

This is a question sent in by a student doing GCE O Level Chemistry Examination:

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?

PS: Let’s us discuss on those questions above. You can leave your answers and suggested solutions in the “COMMENTS” section below.

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Sean Chua
Many know me as the Ten Year Series book author for JC A-Level H2 Chemistry and O-Level Pure Chemistry. My 19+ years of coaching experience (since 1999) with more than 1500 students from 180+ JCs and Secondary Schools has allowed me to understand the true reasons why students are not able to perform well in Chemistry. Most importantly, my strength lies in using everyday analogies (even grandmothers can understand!) to simplify abstract concepts. Also, my teaching methodology has been designed to be fun, enjoyable and effective for my students. If you want to have an enjoyable time learning Chemistry and being motivated to excel in Chemistry, contact me today at 98287357

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Comments

  3. burette, caz’ thatz more accurate and can even give the reading in points.
    in laboratories, mostly a burette is considered an appropriate instrument for adding acids.

  4. basically.. it’s doing it 5 times instead of three .. and a burette is a much more accurate apparatus as compared to the pipette. The 25cm3 may be a little vague, resulting in a higher probability of having experimental errors 🙂

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

  6. 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..

  7. 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

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