Moles! (1 Viewer)

[xwrathbringerx]

Hey guys

1. A sample of iron wire reacts with oxygen to form iron (III) oxide. If 3.58 g of the wire yields 5.00 g of the iron (III) oxide, calculate the percentage purity of the iron.

2. The smelting process of chalcopyrite, CuFeS2, is represented by the following equation:

2CuFeS2(s) + 5O2 --> 2Cu(s) + 2FeO(s) + 4SO2(g)

If 22.0 kg of the chalcopyrite reacts and the percentage yield for this process is 95%, calculate the mass of copper formed.

3. How many moles of (i) magnesium chloride (ii) magnesium ions (iii) chloride ions are there in 16.4 mL 0.117 mol/L magnesium chloride solution?

I have no clue how to do these questions. Cold someone please help?

Thanx!

 

[mtsmahia]

im confused...i understand how to do the maths, but i dont really understand what they are asking for....wtf is % purity??

 

[study-freak]

For Q2, work out the number of moles of chalcopyrite and work out mole ratio of chalcopyrite to copper, and hence calculate the number of moles of copper. Work out 95% of that (I do't know if that 95% is by mass or by moles) and work out your final answer in grams or kilograms.

For Q3, use n=cv to calculate the number of moles of MgCl2. That's your answer for (i).
Then MgCl2(aq)->Mg2+(aq) + 2Cl-(aq).
So work out the mole ratio of MgCl2 to Mg2+ or Cl- and hence work out the number of moles of them present in the solution.