Practical 4 Halogens

7/28/2019 Practical 4 Halogens

1/10

PRACTICAL 4

TOPIC : REACTION OF HALOGENS WITH WATER AND

SODIUM HYDROXIDE

NAME: NUR ARIFAH BT MOHD SABRI

MATRIX NO: DPM0010_2013B

PROGRAMME: DIPLOMA IN PHARMACY BATCH APRIL

2013

SEMESTER : 1

DATE : 12 JUNE 2013

LECTURERS NAME : MADAM ARIESMA RAZANA


2/10

OBJECTIVE : To determine the reaction of halogens with water and sodium hydroxide.

INTRODUCTION :

The Halogens are typical nonmetals and form the 7th Group in the Periodic Table . 'Halogens' means

'salt formers' and the most common compound is sodium chloride which is found from natural

evaporation as huge deposits of 'rock salt' or the even more abundant 'sea salt' in the seas and oceans.

The halogen dissociates in water to form it is respective acid or acids. In sodium hydroxide, since all

halogens are above hydroxides in the electronegative series, they displace the hydroxide to form the

sodiumhalide.

MATERIALS AND APPARATUS :

1. Liquid bromine

2. Liquid chlorine

3. Iodine crystals

4. Distilled water

5. pH paper

6. Dilute sodium hydroxide (0.1M)

7. Test tubes (6 pieces per group)


3/10

8. Dropper

9. Test tube rack

10. 5ml measuring cylinder


4/10

PROCEDURE :

Part A

reaction of halogens with water

I.) With chlorine

1. 5ml of distilled water is poured into a clean test tube. A few drops of liquid chlorine are added into

this test tube.

2. The solution is then tested with pH paper. All observations are recorded.

II.) With bromine

1. 5ml of distilled water is poured into a clean test tube. A few drops of liquid bromine are added into

this test tube.


III.) With iodine

1. 5ml of distilled water is poured into a clean test tube. A small iodine crystal is added into this test

tube.

2. The test tube is then closed with a stopper and shaken well.



5/10

Part B reaction of halogens with sodium hydroxide

I.) Chlorine and sodium hydroxide

1. 5ml of dilute sodium hydroxide is poured into a clean test tube. A few drops of liquid chlorine are

added into this test tube.


3. All observations are recorded.

II.) Bromine and sodium hydroxide

1. 5ml of dilute sodium hydroxide is poured into a clean test tube. A few drops of liquid bromine are

added into this test tube.



III.) Iodine and sodium hydroxide

1. 5ml of dilute sodium hydroxide is poured into a clean test tube. A small iodine crystal is added into

this test tube.



6/10


RESULTS

HALOGEN OBSERVATION

REACTION WITH WATER REATION WITH SODIUM

HYDROXIDE

CHLORINE YELLOW TO BLUE BLUE

BROMINE NOT CHANGE BLUE

IODINE NOT CHANGE BLUE

DISCUSSIONS

i) Halogens react with water to form acid. For example :

Chlorine reacts with water to form hydrochloric acid and hypochlorous acid, a solution that can be used

as a disinfectant or bleach:

Cl2 + H2O ->HCl + HClO

Bromine slowly reacts with water to form hydrogen bromide and hypobromous acid.

Br2 + H2O ->HBr + HBrO

Iodine reacts slightly with water to form hydrogen iodide and hypoiodous acid.

I2 + H2O -> HI + HIO


7/10

The reaction between iodine and water and between bromine and water does not give any changes to

the pH paper because the reaction is too slow.

ii) Halogens react with sodium hydroxide to form salt and water.

Chlorine reacts with sodium hydroxide to form sodium chlorate and water.

Cl2 + 2NaOH ->NaCl + NaOCl + H2O

Bromine reacts with sodium hydroxide to form sodium bromide and water.

Br2 + 2NaOH ->NaBr + NaBrO +H2O

Iodine reacts with sodium hydroxide to form sodium iodide and water.

6NaOH + 3I2 ->5NaI + NaIO3 + 3H2O


8/10

QUESTIONS

1.HALOGEN

REACTION WITH WATER REATION WITH SODIUM

HYDROXIDE

CHLORINE Cl2 + H2O -> HCLO + HCl Cl2 + 2NaOH ----- NaCl + NaOCl +

H2O

BROMINE Br2 + H2O ->HBrO + HBr Br2 + 2NaOH = NaBr + NaBrO

+H2O

IODINE I2 + H2O -> HIO + HI 3I2 + 6NaOH= 5NaI + NaIO3 +

3H2O

2. There are two properties of halogen other than those observed in this experiment . First,halogen have high effective nuclear charge, therefore they are highly electronegative. They gain

an electron through reaction with other elements.

Next, halogens are highly reactive, and will combine directly with almost all elements.

Due to this high level of reactivity, the halogens are almost never found in pure form; rather,

they have to be extracted.

3. The reactivity of halogens based on the periodic table: The halogen elements have sevenvalence electrons,they only require one additional electron to form a full octet. This

characteristic makes them more reactive than other non-metal groups. Halogens are one

electron short in the outermost (p) shell, adding an electron creates a stable configuration,

hence releases energy. The further you go up the halogen series (i.e. bromine->flourine) the

closer the outer orbit is to the nucleus, hence the greater the attraction and hence the higher

the electronegativity of the halogen.


9/10

PRECAUTIONS :

Always ensure that you wear proper fitting clothes and nothing that is too loose. You should also wear

your lab coat to avoid spilling anything on your clothes.

Make sure you read the bottle labels carefully and only use what you are supposed to use during an

experiment. You should not try out anything on your own unless you are very sure of what reagents or

chemicals you need to use and their results

Use rubber stopper to seal the mouth of the test tube.

Make sure that the the test tube is in a clean and dry condition before using it.

Place the eyes perpendicularly to the scale of graduated cylinder during the measuring of distilled

water, sodium hydroxide, chlorine and bromine to avoid parallax error.


10/10

CONCLUSION :

When chlorine react with water , the pH paper turns from yellow to blue. There are no change when

bromine and iodine react with water. When chlorine, bromine and iodine react with sodium hydroxide,

pH paper turns from yellow to blue.

REFERENCES :

1. http://www.docbrown.info/page03/The_Halogens.htm2. http://wiki.answers.com/Q/Reaction_of_halogen_with_water_and_sodium_hydroxide3. http://wiki.answers.com/Q/What_is_the_Equation_for_chlorine_water4. Chemistry for matriculation forth edition semester 1
http://www.docbrown.info/page03/The_Halogens.htmhttp://www.docbrown.info/page03/The_Halogens.htmhttp://wiki.answers.com/Q/Reaction_of_halogen_with_water_and_sodium_hydroxidehttp://wiki.answers.com/Q/Reaction_of_halogen_with_water_and_sodium_hydroxidehttp://wiki.answers.com/Q/What_is_the_Equation_for_chlorine_waterhttp://wiki.answers.com/Q/What_is_the_Equation_for_chlorine_waterhttp://wiki.answers.com/Q/What_is_the_Equation_for_chlorine_waterhttp://wiki.answers.com/Q/Reaction_of_halogen_with_water_and_sodium_hydroxidehttp://www.docbrown.info/page03/The_Halogens.htm

Documents

Practical 4 Halogens