- Reaction (if any) of chloride with bromine and iodine solution
- About 1mL of Potassium chloride solution is added to each of two test tubes
- About the same volume of bromine water is added to one of these tubes and the other was added with the same volume of iodine solution
- The test tubes is shake and the color changes is noted-(if any)
- A few drops of hexane are added to each tube, shake and allow it to settle and the color of each layer is noted.
- Reaction that taken place is observed and a copy of result are completed in table 11.1
Results:
Discussions:
Halogens act as oxidizing agents (electron acceptors) in the majority of their reactions.
X2 + 2 e 2 X-(aq)
When going down the group, the atomic size increases. As the atomic size increases, the ns2np5 valence electron in outermost shell is further apart from the nucleus. Thus the electronegativity decreases down the group. As the electronegativity decreased the oxidizing power of the halogens also decreases because of the size of the element and the electron affinity as well as hydration energy decreases. The halogens which are higher in the group can oxidize halide ions lower in the group. The arrangements of elements of group 17 according to periodic table is Fluorine,Chlorine,Bromine,Iodine and Astatine. Since Fluorine, F2 is higher in the group it is the strongest oxidizing agent in halogens group. It can oxidize chloride ion. This is obviously a redox reaction in which oxidation and reduction occurs simultaneously.
F2 + 2 Cl- 2 F- + Cl2
In this experiment iodide reacted with chlorine and bromine water. Normally iodide, bromide and chloride ions will be in an aqueous solution.
When iodide ions react with chlorine water, chlorine oxidised iodide ions from potassium iodide solution to iodine. The iodine appears either as a red solution if you are mean with the amount of chlorine you use, or as a dark grey precipitate if the chlorine is in excess. So chlorine act as the oxidizing agent in this reaction.
When iodide ions react with bromine water, bromine oxidized iodide ions from potassium iodide solution to iodine. A red solution of iodine is formed. So bromine acts as an oxidizing agent in this reaction.
Br2 + 2 I- 2 Br- + I2
When bromide ions react with chlorine water, chlorine oxidised bromide ions from potassium bromide solution to bromine. The bromine appears as an orange solution. So Chlorine acts as an oxidising agent in this reaction.
When bromide ions react with iodine solution, iodine will not oxidise bromide ions from potassium bromide to bromine because iodine is lowest element in the group compare with bromine, it does not strong enough to oxidise bromide ions. Thus no reaction occurs between bromide ions and iodine solution.
When chloride reacts with bromine water and iodine solution there will be no reaction because chloride ion is the strongest oxidising agent than bromide and iodide ions. Bromine and iodine cannot oxidize chloride ions to chlorine because they are does not strong oxidizing agent.Furthermore, Bromine and iodine are lower in the group ,so it cannot oxidize the halide ion which is higher than it in the group. Therefore there will be no colour changes in that reaction.
Br2 + 2 Cl- no reaction
I2 + 2 Cl- no reaction
During the experiment, hexane was added into the halogen halide solution. This is because hexane can used to determine the type of halogens molecules which present in the solution according to the colour change. In the reaction of iodide ions with chlorine and bromine, iodine has been extracted from the solution after adding hexane. That means iodide ion is displaced by chlorine and bromine. For the reaction of bromide ion with chlorine and iodine, only Br2 will extracted from chlorine solution after shake with hexane, and the bromine ions cannot be displaced by iodine because of the oxidizing power. For the reaction between chloride ion with bromine and iodine, there has no any reaction occur, and the bromine and iodine are extracted from both solutions respectively. From there, it can know that chloride ions cannot displace by any of bromine and iodine. Hence, the strongest oxidizing agent is chlorine, follow by bromine and iodine.
I2 < Br2 < Cl2
Questions:
1.
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I2 (aq KI) does not oxidize Cl- (aq)and Br-(aq)
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Br2 (aq) does not oxidize Cl- (aq) but oxidize I-(aq)
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Cl2 oxidize Br-(aq) and I-(aq)
2.
- Chlorine can oxidized the bromide ions in potassium bromide aqueous solution and also iodide ions in potassium iodide aqueous solution.
-
Cl2 + 2Br- 2Cl- + Br2
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Cl2 + 2I- 2Cl- + I2
- Bromine can oxidized the iodide ions in potassium iodide aqueous solution
-
Br2 + 2I- 2Br- + I2
3.
I2 < Br2 < Cl2
References:
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www.chemguide.co.uk/inorganic/group7/halogensasoas.html
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- dwb4.unl.edu/ChemSource/SourceBook/119HALO.pdf
- textbook.s-anand.net/ncert/class-11/chemistry/8-redox-reactions
- faculty.lacitycollege.edu/boanta/LAB101/.../periodic%20properties.d...