Just another Sig Fig Question

[Romperait]

And it's the same with this question as well (Calc the amount of Cl in mol in a 34 g sample of FeCl3):

Step 1. Calc the amount of FeCl3
          = 0.2095 mol

Step 2. As each mole of FeCl3 contains 3 mol of Cl- ions, calc the amount of Cl- ions.

n(Cl-) = 3 x 0.2095 = 0.628mol

Step 3. Correct number of sig figs.

n(Cl-) = 0.63mol < Why 2 sig figs? >.< Gaah.


Thank you for putting up with me but this is all so frustrating when you don't get it lol.

It's 2 significant figures because you are given a 34g sample of FeCl3.

[stonecold]

Yeah, what Romperait said.

And from my experience this year, I only believe you will lose a mark for incorrect sig.figs/states on the question that is designated.

So say Q2 says "give your answer to an appropriate number of significant figures" and you do, and then in Q5 you go one digit too many, I doubt you'll be punished, because Q5 did not specify to answer to the correct number of significant figures.

Also, I'd say the majority of teachers wouldn't even know the sig fig rules accept for the main multiplication and division one.  My teacher marked exams and she didn't know the others.

[dptjandra]

Well, from memory, only the multiplication/division and addition/subtraction rules are given in the examiner's report - the others are covered in uni textbooks (ironically, we didn't do them in chem, but in physics!)