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# Moles Watch

1. Can someone please help me on this question because I'm not sure which moles value to use and why:
2. You have to work out which reactant is limiting first. You need 2 moles of HCl for one mole ZnO.
3. (Original post by Jennifer50)
Can someone please help me on this question because I'm not sure which moles value to use and why:
calculate the number of moles of HCL: 1.2 mol.

Find the limiting reagent: 1.2/2 = 0.06 mol (concentration x volume)/2

This is the limiting reagent and this means that ZnO is in excess. So you use the number of mol of the limiting reagent.

Therefore, you will get 0.06 mol of ZnCl2 produced and you just take 0.06 x Mr of ZnCl2.

Hope this helps! And is this aqa new spec?
4. (Original post by rosemondtan)
calculate the number of moles of HCL: 0.06 mol (concentration x volume)/2

This is the limiting reagent and this means that ZnO is in excess. So you use the number of mol of the limiting reagent.

Therefore, you will get 0.06 mol of ZnCl2 produced and you just take 0.06 x Mr of ZnCl2.

Hope this helps! And is this aqa new spec?
Number of moles of HCl is 1.2 mol, not 0.6 mol. Is assume you're just trying to show which reactant is limiting though?
5. (Original post by B_9710)
Number of moles of HCl is 1.2 mol, not 0.6 mol. Is assume you're just trying to show which reactant is limiting though?
oops yup! Thanks for the correction

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