Identification of gases
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If there is no change to the colour of litmus paper after testing for gases using the moist litmus paper, what does it mean and what do you then test it with?
It means the gas is neutral. You test it with lighted splint and a glowing splint. If it ‘pops’ with a lighted splint —> it means the gas is hydrogen If it ‘relights’ with a glowing splint—> it means the gas is oxygen
If, after testing for gases using the moist litmus paper and the moist red litmus paper turns blue, what does it mean
It means the gas is an alkaline The gas is most likely ammonia, NH3
If, after testing for gases using the moist blue litmus paper and it turns red, what does it mean and what do you do next?
It means the gas is acidic We then pass the gas through limewater or pass the gas through aqueous acidified potassium manganate (VII) If, after passing the gas through limewater and it gives a white precipitate with limewater, it means the gas is carbon dioxide. (CO2) If, after passing the gas through aqueous acidified potassium manganate (VII) and it turns aqueous acidified potassium manganate (VII) from purple to colourless, it means the gas is sulfur dioxide (SO2)
What should the blank be? Na 2 SO 3 + 2 HCL—>
Na 2 SO 3 + 2 HCL —> 2NaCl + SO 2 + H2O
What should the blank be? Zn + H2SO4 —>____________
Zn + H2SO4 —> Zn SO4 + H 2
What should the blank be? 2 H2O2 —> ___________
2 H2O2 —> 2H2O + O2
What should the blank be? CaCO3 + HCl —> ______________
CaCO3 + HCl —> CaCl2 + CO 2 + H2O
What should the blank be? NH4Cl + NaOH –> _____________
NH4Cl + NaOH –>NH3 + NaCl + H2O
What should the blank be? NaClO + 2 HCl –> ________________
NaClO + 2HCl –> NaCl + Cl2 + H2O
What should you take note when heating something in a test tube?
• The test-tube holder should be clipped about 1cm below the mouth of the test-tube, NOT at the middle of the test-tube. • When heating, move the test-tube gently, ensuring the whole mixture is heated, NOT just one spot. • When heating, the test-tube should be held about 45 degrees to the flame and the mouth should be pointed away from others. • When testing the gas with litmus paper, the paper should be held at the mouth of the test-tube, WITHOUT touching the test-tube.