# Can someone spot the error in the question?

#### lioric

Summary
This is a question from a local exam paper.
I can see a huge error in the question
Can someone confirm this error.

#### TeethWhitener

Gold Member
Well, you made an error saying that hydrated copper sulfate was gray:
https://en.wikipedia.org/wiki/Copper(II)_sulfate
You also made an error when you said you were going to melt copper sulfate over a flame (it decomposes to sulfur trioxide and copper oxide without melting).

But yes, there seems to be an error in the mass in part d. I'm assuming that's what you were talking about.

#### lioric

But yes, there seems to be an error in the mass in part d. I'm assuming that's what you were talking about.
Yes. I wanted to make sure that it was a typo that the teacher made
Also look at the last answer
Technically the student is correct. Since amount of water lost was to be divided by the total mass in the beginning of the question.
It's not the student's fault that the numerator is greater than the denominator. That happened because of the typo in the question.

BTW this is the question paper of my student. I helped her study for her high school exam.
If it was me, I would have complained about the question in the exam Hall. I wouldn't have written the answer to the wrong question.

#### TeethWhitener

Gold Member
I’m a bit surprised that the percent in part (e) they’d be interested in is a mass percent. If you convert the masses to moles, you find that there are 5 waters per CuSO4 molar unit, which is actually the case for hydrated copper sulfate. It’s a well-written question if you get rid of the mistakes.

#### lioric

I’m a bit surprised that the percent in part (e) they’d be interested in is a mass percent. If you convert the masses to moles, you find that there are 5 waters per CuSO4 molar unit, which is actually the case for hydrated copper sulfate. It’s a well-written question if you get rid of the mistakes.
Of course it's well written it was copied from an olevel paper. The teacher just changed the substance and masses.

"Can someone spot the error in the question?"

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