# Question on colour intensityWatch

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#1
Right, I've been literally banging my head on the wall over this.
A transition metal ion, M, reacts with a complexing agent, L, to form a coloured complex with the formula ML2 .

Portions of a 0.05 mol dm−3 solution of M were mixed with portions of a 0.05 mol dm−3 solution of L, so that the total volume of the resulting mixture was always 10 cm3 .

The colour intensities of the complex in these mixtures were measured using a colorimeter.

What would the graph of the results look like? 0
2 years ago
#2
Both M and L are presumably colourless when alone.

Hence, you know that both the extremes on the x axis will have intensity values at a minumum. That rules out D.

The maximum colour intensity will be obtained when the maximum amount of ML2 is present. You need to work out when that will be with respect to the proportions of the two solutions. As the concentrations of each are equal, that is easier.

Graph A says that the maximum amount of ML2 is present when there is an equal concentration of M and L.
Graph B says that the maximum amount of ML2 is present when there is 2 times as much L as there is M.
Graph C says that the maximum amount of ML2 is present when there is 2 times as much M as there is L.

The question really boils down to answering the question: Given the same overall concentration of M+L, what is the optimal ratio for the creation of ML2?
0
#3
(Original post by Infraspecies)
Both M and L are presumably colourless when alone.

Hence, you know that both the extremes on the x axis will have intensity values at a minumum. That rules out D.

The maximum colour intensity will be obtained when the maximum amount of ML2 is present. You need to work out when that will be with respect to the proportions of the two solutions. As the concentrations of each are equal, that is easier.

Graph A says that the maximum amount of ML2 is present when there is an equal concentration of M and L.
Graph B says that the maximum amount of ML2 is present when there is 2 times as much L as there is M.
Graph C says that the maximum amount of ML2 is present when there is 2 times as much M as there is L.

The question really boils down to answering the question: Given the same overall concentration of M+L, what is the optimal ratio for the creation of ML2?
Ahh, so looking at their M:L 1:2 ratio, it cannot be C because that would just be second most intense colour to B.
In what scenario would A be the answer? when the molecular formula is 1:1 ratio? (and equal concentration)
0
2 years ago
#4
(Original post by CaptainJackFail)
Ahh, so looking at their M:L 1:2 ratio, it cannot be C because that would just be second most intense colour to B .
In what scenario would A be the answer? when the molecular formula is 1:1 ratio? (and equal concentration)
B is most coloured yes.

And yes, that is when A is the answer.

I don't know what you mean 'it cannot be C because that would just be the second most intense colour to B'. C is just false.
0
#5
(Original post by Infraspecies)
B is most coloured yes.

And yes, that is when A is the answer.

I don't know what you mean 'it cannot be C because that would just be the second most intense colour to B'. C is just false.
Oh, yeah you're right, the graph of C makes no sense when looking at the ratio, apologies and thanks for the clarification. 0
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