Silly chemistry question :( Watch

anonymous14
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Hello,

Well, I have a question (Chemistry), 'why should you wait for the reaction to finish reacting completely?' (The reaction in this case is between copper sulfate and magnesium.)

I am curious to know, because this question appeared in a Chemistry test which I did this week, I did write an answer for this, but I would like to know how other people would approach this question.

Thank you to anyone who replies
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addylad
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To ensure that the results are accurate? Especially if you are measuring pH, volume of gas given off, etc.
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anonymous14
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(Original post by addylad)
To ensure that the results are accurate
I feel slightly relieved,as I wrote something similar to this.
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Unkempt_One
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What was the context of the question?
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anonymous14
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(Original post by Unkempt_One)
What was the context of the question?
The question was:

'In the reaction between copper sulfate and magnesium, why must you wait for the magnesium to react completely ?'

(The test was regarding exothermic and edothermic reactions.)
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Unkempt_One
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Oh, right. Erm, presumably it's something to do with being sure of the full extent of the temperature change? It completely depends on so many other problems though, is it for an experiment or just a demo? If it's for an experiment you must always wait for every reaction to complete, otherwise the results will not be comparable as a variable not being compared isn't being properly controlled.
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amy.qtr
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To make sure that the results completely are finished.
This is because sometimes results do vary within time and in this case it can be within seconds. So if your test was 11 seconds the 9tth can have a different result to what it would have in 11

Not a stupid question , but it was stupid to say that it was stupid lol -)
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Unkempt_One
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(Original post by amy.qtr)
To make sure that the results completely are finished.
This is because sometimes results do vary within time and in this case it can be within seconds. So if your test was 11 seconds the 9tth can have a different result to what it would have in 11

Not a stupid question , but it was stupid to say that it was stupid lol -)
We weren't given enough background information on the experiment to say whether it was a stupid question or not. I hate this type of question because the answer is always so simple yet I always search for underlying explanations when I don't need to.

Why do you ensure the reaction is finished completely?

To ensure the result has finished completely.

Why do you wait for the result to finish completely?

Because the results can vary with time.

Why do we care if the results vary with time?

Because we need to make sure the temperature change for each result is scientifically comparable.

What defines scientific comparibility in the case of endothermic/exothermic reactions?

Being able to ensure all variables except the temperature change are controlled.

But what about the time it takes for the reaction to finish? Is that not also varying?

E-e-e-ettoh . . .
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