Redox reactions chlorine water

In summary, Homework Equations state that an unknown ionic solution could be either NaI (aq), AgCl, ZnI2 or CuBr2. Question 1 found that adding Br2 (aq) to the solution caused it to turn red-brown in color, while question 2 found that when chlorine water was added to the sample, the solution changed to a straw brown color. The unknown solution is most likely to be KI (aq) or KBr (aq) or Br2 (aq) or F2(aq).
  • #1
paperdoll
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Homework Statement



I am having trouble trying to find out if things react with each other or not. I don't really know how to read the reactivity series well :confused:

Homework Equations


Question 1: a student was given a beaker of an unknown ionic solution to identify. she conducted the following tests:

1. add br2 (aq): mixture turns red-brown colour
2. add Al(s): no observed change to solution or metal

the unknown ionic solution could be:
NaI (aq), AgCl, ZnI2 or CuBr2

Question 2:
when chlorine water is added to a sample of colourless ionic solution, the solution changed to a straw brown colour. The unknown solution is most likely to be:

KI(aq) or KBr (aq) or Br2 (aq) or F2(aq)

The Attempt at a Solution


For question 1,I know that aluminium usually likes to give away electrons so the answer is likely to be NaI? because Na is a stronger reducing agent than Al I think.

For question 2
I can eliminate Br2 and F2 since they are not ionic but I am stumped on the other two possible answers.
 
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  • #2
Hi paperdoll! :smile:

I have a picture here that may help you:
enegtrend.jpg
With Na to the far left, you know that it will ionize in water immediately.
(Think of NaCl salt that easily dissolves.)

What Al far into the direction of the arrow, you know that Al will bind to any negative ion easily.
(Al will typically oxidize.)

With Br slightly ahead of I, Br would bind more tightly than I.
 
  • #3
I like Serena said:
Hi paperdoll! :smile:

I have a picture here that may help you:
enegtrend.jpg



With Na to the far left, you know that it will ionize in water immediately.
(Think of NaCl salt that easily dissolves.)

What Al far into the direction of the arrow, you know that Al will bind to any negative ion easily.
(Al will typically oxidize.)

With Br slightly ahead of I, Br would bind more tightly than I.

I understand the Na and the Al but I still don't understand Br and I. On my reduction potentials table Br is +1.07 and I is +0.54. But in this case, Br- would want to go to Br (l) which is a oxidation reaction. So wouldn't I be better at oxidation than Br? a bit confused :confused:
 
  • #4
paperdoll said:
I understand the Na and the Al but I still don't understand Br and I. On my reduction potentials table Br is +1.07 and I is +0.54. But in this case, Br- would want to go to Br (l) which is a oxidation reaction. So wouldn't I be better at oxidation than Br? a bit confused :confused:

I think you have it the wrong way around.

A high reduction potential means a strong tendency to attract an electron (and thereby reduce the charge).
In an oxidation reaction Br becomes Br- (just like in regular oxidation O becomes O2-).

So Br is better at oxidation (becoming Br-) than I is.

You'll see that Na has a strongly negative reduction potential (strong tendency Na → Na+).
Al has a less negative reduction potential (Al → Al3+).
I has a positive reduction potential (I → I-).
And Br has a more strongly positive reduction potential (stronger tendency Br → Br-).
 
Last edited:
  • #5


Redox reactions involving chlorine water can be quite complex, as chlorine can act as both an oxidizing agent and a reducing agent. In the first question, it is important to understand that chlorine water is a strong oxidizing agent, meaning it has a high tendency to accept electrons from other substances. This can be seen in the reaction with br2 (aq) where the chlorine water is reduced to form a red-brown color.

In terms of the unknown solution, it is important to consider the reactivity series, which is a list of elements in order of their tendency to give away electrons. In this case, aluminium is higher on the reactivity series than sodium, so it is not likely that the unknown solution is NaI (aq). It is possible that the unknown solution is ZnI2 or CuBr2, as both zinc and copper are lower on the reactivity series than aluminium and can therefore be oxidized by chlorine water.

For question 2, the fact that the solution changed to a straw brown color indicates that the chlorine water is acting as an oxidizing agent. This means that the unknown solution is most likely KBr (aq), as bromide ions can be easily oxidized by chlorine water to form a brown color. KI (aq) is also a possibility, but it is less likely as iodide ions are not easily oxidized by chlorine water. It is important to remember that the reactivity series is not the only factor to consider in redox reactions, as the chemical properties of the specific ions involved also play a role.
 

What is a redox reaction?

A redox reaction is a chemical reaction in which electrons are transferred from one substance to another. This transfer of electrons results in the oxidation of one substance and the reduction of another.

How does chlorine water participate in redox reactions?

Chlorine water, also known as hypochlorous acid, can participate in redox reactions as both an oxidizing agent and a reducing agent. This means that it can either lose or gain electrons, depending on the other substances involved in the reaction.

What are the products of a redox reaction involving chlorine water?

The products of a redox reaction involving chlorine water will depend on the other substances involved. Generally, the products will be a chloride ion and either a water molecule or a hydroxide ion, depending on whether the chlorine water acts as an oxidizing or reducing agent.

Is chlorine water safe to use in redox reactions?

Chlorine water can be dangerous if not handled properly. It is a strong oxidizing agent and can cause skin and eye irritation. It should only be used by trained professionals in a controlled laboratory setting.

What are some common applications of redox reactions involving chlorine water?

Redox reactions involving chlorine water have a variety of applications, including water treatment, disinfection of surfaces and equipment, and production of bleach and other cleaning products. It is also used in organic synthesis and as a bleaching agent in the paper and textile industries.

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