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List of cation to be tested

Brown precipitate formed when added with sodium hydroxide or ammonia solution. Fe3+ is present.

Dirty green precipitate formed when added with sodium hydroxide or ammonia solution. Fe2+ is present.

Cu2+ dissolve in excess of ammonia solution to form dark blue solution.

Blue precipitate is formed when Cu2+ is added with sodium hydroxide or ammonia solution.

This picture shows the comparison between Cu2+ in ammonia solution (light blue precipitate) and Cu2+ in excess of ammonia solution (dark blue solution).

When Fe3+ is added with potassium thiocyanate (KSCN), blood red colour is observed.

When Pb2+ is added with potassium iodide (KI), yellow precipitate is observed.

When ammonium ion (NH4+) is added with Nessler's Reagent, brown precipitate is observed.

Form 4 Chapter 8: Anion Test - Test for the present of nitrate ion - Brown ring

When solution with nitrate ion is added with dilute sulphuric acid and iron(II) sulphate, then followed by a few drops of concentrated sulphuric acid, a brown ring will formed.

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chapter 8 Form 4: Salts

Below are some pictures of the solutions.

Iron(II) sulphate

Iron(III) chloride

Ammonium Chloride

Lead(II) nitrate

Zinc nitrate

Magnesium nitrate

Copper(II) sulphate

Calcium nitrate

Aluminium nitrate

Potassium iodide

Potassium thiocynate

Nessler's Reagent

Aqueous ammonia

Our Chemistry Lab Memories

Special Pictures

On 3 May 2010, I spotted a baby bird by the corridor on the way to chemistry lab. It's was so cute and looked heavy. I guess it can't fly yet.

22 July 2010, the 6B1 students found a beetle on a student's table. I quickly took a picture of it before my camera running out of battery.

To investigate the combustion of metals in oxygen

Aim :
To investigate the combustion of metals in oxygen

Procedure :
1.    A piece of  5 cm magnesium ribbon is cleaned with sandpaper.
2.    The magnesium ribbon is held with a pair of tongs and lit in the Bunsen burner.
3.    It is quickly placed into a gas filled with oxygen.
4.    Any changes that occurs are recorded.

The white powder formed is magnesium oxide.

Magnesium oxide is formed.

Special thanks to ace_0106 for typing the procedure.

Experiment 3.2: To Study Redox Reaction in terms of Displacement Reaction of a Metal from its Salt Solution

Aim :
To study the redox reaction in terms of displacement reaction of a metal from its salt solution.

Procedure :
1.    A strip of zinc plate and a strip of copper plate are cleaned with sandpaper.
2.    The zinc plate is then immersed in the copper(II) sulphate solution (test tube P) and the copper plate is immersed in silver nitrate solution (test tube Q).
3.    The mixture is left aside for half an hour.
4.    The changes that take place on the zinc plate, the copper plate, and in the copper(II) sulphate solution and the silver nitrate solution are recorded.

Special Thanks to ace_0106 for typing the procedures.

*Test tube P
Zinc plate in copper(II) sulphate solution.

Copper metal is deposited on the zinc plate. The blue colour fades as the concentration of Cu2+ ions decreases.

*test tube Q
The shining silver metal is precipitated on copper plate.

Experiment 3.3: To Study the Displacement Reaction Between Halogens and Halide Ions

Aim :
To study the displacement reactions between halogens and halide ions

Procedure :
1.    A test tube is filled with 2 cm3 of potassium bromide, KBr solution.
2.    2 cm3 of chlorine water is added to the potassium bromide solution. The mixture is shaken gently.
3.    2 cm3 of 1,1,1,-trichloromethane (CH3CCl3) is then added to the misture obtained in step 2. The mixture is then shaken vigorously.
 4.    The test tube is allowed to stand for a few minutes and the colour of the 1,1,1,-trichloromethane layer is recorded.

5.    Steps 1 to 4 are repeated using the following mixtures.

a)    Chlorine water and potassium iodide, KI solution
b)    Liquid bromine and potassium chloride, KCl solution
c)    Liquid bromine and potassium iodide solution
d)    Iodine solution and potassium bromide solution
e)    Iodine solution and potassium chloride solution

A special thanks to ace_0106 for typing the procedures.

Br2 + KCl  no displacement occur.

Activities 2.6 To Prepare Ethyl Ethanoate

Aim :
To study the chemical properties of ethanoic acid (reaction between ethanoic acid and alcohol)   

Procedure :
1.    2 cm3 of ethanoic acid is poured into a test tube.
2.    4 cm3 of pure ethanol is added to the ethanoic acid.
3.    By using a dropper, four drops of concentrated sulphuric acid are added slowly and carefully to the mixture. The resulting solution is shaken gently.
(Precaution : concentrated sulphuric acid is very corrosive !!!)

4.    The reaction mixture is heated slowly and carefully until it boils. The test tube is shaken continuously.
5.    The contents of the test tube is poured into a beaker half-filled with water.
6.    The odour, colur and solubility of the organic product is obtained and recorded.

The distillate is a colourless liquid and with a fragrant odour. The liquid is insoluble in water and floats on water.
•    organic product (ester)- ethyl ethanoate

Activities 2.4 To Investigate the Properties of Ethanol

Aim :
To investigate the properties of alcohol

Procedure :
(A) Combustion of ethanol in air

1. About 1 cm3 of ethanol is added to an evaporating dish.
2. The ethanol is ignited using a lighted wooden splint.
3. The flammability of ethanol and the nature of the flame is observed.

(B) Oxidation of ethanol

1. The boiling tube is filled with approximately 5 cm3 of potassium dichromate(VI) solution, K2Cr2O7.
2. About 5 cm3 of dilute sulphuric acid is added to the potassium dichromate(VI) solution.
3. About 5 cm3 of ethanol is added to the acidified potassium dichromate(VI) solution.

4. A rubber stopper fitted with a delivery tube is inserted into the boiling tube. The delivery tube is inserted into a test tube placed in a beaker half-filled with ice cold water.

5. The mixture of ethanol and acidified potassium dichromate(VI) ios boiled slowly. The distillate is collected in the test tube.

6. The distillate is tested with a piece of blue litmus paper.
A colourless distillate is obtained.
The property of the distillate is acidic. It turns blue litmus paper red.

The orange colour of acidified potassium dichromate(VI) turns green.
The distillate has a vineger smell. Ethanoic acid is produced.

(C) Dehydration of ethanol

1. About 2 cm3 of ethanol is put into a dry test tube.
2. A small amount of glass wool is inserted into the test tube to absorb the ethanol.
3. Some porcelain chips are placed in the middle section of the test tube.

4. The test tube is closed with a rubber stopper fitted with a delivery tube. Another test tube is filled with water and inverted into a beaker.
5. The porcelain chips are heated strongly. The Bunsen burner flame is then shifted to the glass wool to vaporise the ethanol absorned in it.

6. The gas released is collected in two set test tubes.The following tests are carried out on the gas collected.

A) The flammability of the gas
B) The reaction of the gas with liquid bromine