Tests for gases
Apparatus:
* Test tubes
* Test tubes rack
* Red litmus paper
* Gauze map
* Tripods
* Bunsen Burner
* Test tubes clip
* Safety map
* Dropper
* Beaker
* Lab coat
* Safety goggles
* Lighter
* Dilute acid (HNO3)
* Silver nitrate (Ag NO3)
* Lead (II) Nitrate (PbNO3 )
* Sodium hydroxide (NaOH)
* Aluminium foil
* Barium Nitrate (BaNO3)
* Limewater
* Solution 1
* Solution 2
* Solution 3
* Solution 4
* Solution 5
Safety:
* Always wear goggles to provide protection for eyes.
* Always wear a lab coat to provide protection for clothing
* Girls should always tie back long hair during the experiment.
* When something gets into eyes, immediately flush it out by lots of water.
* Wash hands thoroughly before leave the lab after all lab work is finished.
* HNO3 is a kind of strong acid, though it has been diluted, but we still have to be careful when we are using it.
*Always clean up the lab and all apparatus after use, and dispose of substances according to proper disposal methods.
Method:
Test for the anions
Test for aqueous cations
Results:
SULUTION1:
SOLUTION2:
SOLUTION 3:
SOLUTION 4:
SOLUTION 5:
From the 5 tables, we can say that: Solution1 = Copper Carbonate
Solution 2 = Calcium Chloride
Solution 3 = Iron Sulphate
Solution 4 = Iodide
Solution 5 = Ammonium Carbonate
Discussion:
Theory
Cations – the charged of particles are called ions, the positive ions are called cations because they travel towards the cathode. Some metals are more reactive than others. The ions of very reactive metals are difficult to discharge. Sodium is a very reactive metal. When it reacts, sodium atoms form sodium ions. It is hard to force a sodium ion to accept an electron and turn back into a sodium atom. Hydrogen ions are discharges in preference to sodium ions, the ions of less reactive metals, such as copper and lead, are easy to discharge.
Anions - the Negative ions are called anions because they travel towards the anode. Sulphate ions and nitrate ions are very difficult to discharge. When solutions of sulphates and nitrates are electrolyzed, hydroxide ions are discharged instead, and oxygen is evolved.
What do “cations” and “anions” mean?
Cations are the charged particles that contain positive ions and anion are the charged particles that contain negative ions.
How can we test for the carbon dioxide that has been formed?
We can test it by adding limewater into the solutions, if the solutions change the color to milky white that means the solution contains carbon dioxide. If we can to get a more correct result, we can use a rubber cork to block the test tubes to keep the carbon dioxide inside the test tubes, then we can observe the color change more clearly, because the more carbon dioxide in the test tube the greater color changed of the solution.
How can we test for the ammonia that has been formed?
We can test it by heating up the solutions, and put piece of red litmus paper near the test tube, and observe the color change of the litmus paper. If the color don’t change, that means the solution doesn’t contain ammonia, if the color changes from red to blue that means the solution contains ammonia, ammonia is a base gas, so it changes red litmus paper blue.
How come we used dilute acid but not acid?
We used dilute hydrogen nitrate during this experiment, because when a strong acid is reacting, it will react with the substances very fast and strongly, so it is quite dangerous. We used the dilute acid, because the acid has been dissociated, it releases less hydrogen ion, so it reacts with substance much slowly, so it won’t be that dangerous.
Conclusion:
This experiment shows that we can find out the solutions by testing the anions and cations. After we found out the cations and anions, we can know what the solution is by add the two ions together. Such as: we find out the cations of solution2 is Calcium and the anions of solution2 is Chloride, so we can know that solution2 should be Calcium Chloride (Ca2Cl). We can know that by Cations + Anions.
From this experiment, we knew that, we can use lots of different kinds of tests to test the cations and anions. And we can find out what the solutions or substances are after we find out their cations and anions.
Evaluation:
