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Revision notes - Test For Gases and Ions
- Essay length: 858 words
- Submitted: 29/04/2012
-
Marked by teacher:
Kathryn Bradley
Teacher essay summary
This is an excellent summary of the different tests for gases and ions. This work deserves 4/5 but with a few minor changes could easily reach 5/5.
- structure is a little odd in places, resulting in repetition. Differentiation within the ion section would help with this.
- there should be greater use of chemical equations, as generally this helps with explanations.
Additionally, some explanation as to why various tests give certain results would be beneficial. Many exam papers ask you to explain the tests and observations, as well as simply asking you to state them.
Marked by teacher Kathryn Bradley 24/09/2012
The first 200 words of this essay...
Tests for Gases
Name
Formula
Test
Observations
Hydrogen
H2
Ignite gas.
Squeaky pop is heard.
Oxygen
O2
Place a glowing splint in a sample of the gas.
The glowing splint relights.
Carbon dioxide
CO2
Bubble gas through limewater (saturated solution of calcium hydroxide)
A solution turns from colourless to cloudy. A white (milky) precipitate of calcium carbonate forms which is sparingly soluble.
Ammonia
NH3
Test for gas using damp red litmus paper.
Litmus paper turns blue.
Chlorine
Cl2
Test 1
Test for gas using damp litmus paper (red or blue)
Chlorine bleaches the litmus paper very quickly.
Test 2
Test for gas using moist starch-iodide paper.
The paper turns blue-black.
Test 3
Pass gas through a solution of a bromide.
The solution turns from colourless to orange.
Test 4
Pass gas through a solution of an iodide.
The solution turns from colourless to brown (possibly with a black precipitate, iodine).
Nitrogen dioxide
NO2
Not many tests for this gas.
The gas is
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MbT essay summary
This is an excellent summary of the different tests for gases and ions. This work deserves 4/5 but with a few minor changes could easily reach 5/5.
- structure is a little odd in places, resulting in repetition. Differentiation within the ion section would help with this.
- there should be greater use of chemical equations, as generally this helps with explanations.
Additionally, some explanation as to why various tests give certain results would be beneficial. Many exam papers ask you to explain the tests and observations, as well as simply asking you to state them.
