# Chemistry June 2022 help

A typical sample of limestone contains 95.0% by mass of calcium carbonate, CaCO3.
Fertiliser Z, Ca5NH4(NO3)11•10H2O (Mr = 1080.5gmol–1) can be made from limestone. Calculate the mass, in g, of limestone needed to make 1.50 kg of fertiliser Z.
1. Work out moles of fertiliser needed
2. Moles of calcium
3. Work out moles of calcium carbonate to contain moles of calcium.
4. Convert to mass of calcium carbonate
5. / 95. *100
Brev work it out please I can’t seem to get it
Brev work it out please I can’t seem to get it (Original post by Old man1234)1. Work out moles of fertiliser needed
2. Moles of calcium
3. Work out moles of calcium carbonate to contain moles of calcium.
4. Convert to mass of calcium carbonate
5. / 95. *100
1. 1500 / 1080.5 = x
2. 5X
3. 5X x 100.1 = y
4. Y /95 x 100 = answer

Try that should be about 140 g.
(edited 3 weeks ago)
on the mark scheme is says to times the moles of calcium by 5 to work out the mass, but where does the 5 come from?
Original post by lol12348
on the mark scheme is says to times the moles of calcium by 5 to work out the mass, but where does the 5 come from?

The five after Ca in the formula of Z. Sorry I missed that originally.
Original post by Old man1234
1. 1500 / 1080.5 = x
2. X
3. X x 100.1 = y
4. Y /95 x 100 = answer
Try that should be about 140 g.

Why do we divide it by 95 and times it by 100 to get the whole mass of limestone. I don’t get it
Original post by Llalib
Why do we divide it by 95 and times it by 100 to get the whole mass of limestone. I don’t get it
The answer to my step 3 gives the mass of calcium carbonate needed. 95 % of limestone is calcium carbonate so divide by 95 x 100 to get 100% mass of limestone needed.
Original post by Old man1234
The answer to my step 3 gives the mass of calcium carbonate needed. 95 % of limestone is calcium carbonate so divide by 95 x 100 to get 100% mass of limestone needed.