Question

2 MOLES OF ZINC REACTS WITH A CUPRIC CHLORIDE SOLUTION CONTAINING 6.023×10²² FORMULA UNITS OF CuCl2 calculate the moles of copper obtained

Answer 1

First write down the equation that takes place:

          Zn +  CuCl2 ---------->  ZnCl2 + Cu

There 1 mole of Zn will react with 1 mole of CuCl2 to give 1 mole of Cu.

From the question we have 2 moles of zinc, and 
CuCl2 has 6.023x10^22 formula units(calculate its moles)

If       6.023x10^23 (avagadro's constant) = 1 mole
then, 6.023x10^22                       =  1 mole x 6.023 x10^22/6.023x10^23
                                                     =  1 mole x 10^22/10^23
                                                     = 1 mole x 10^-1
                                                      =  0.1 moles
Find the limiting factor as not all the Zinc will react with the cupric chloride:
Since 1 mole of zinc requires 1 mole of CuCl2 to give 1 mole of copper, while in this case there is only 0.1 moles of CuCl2, then CuCl2 is the limiting factor and is what we use for the calculation as follows:

If 1 mole of CuCl2 gives 1 mole of Cu.
Then how much  will 0.1 mole of CuCl2 give = 1mole x 0.1 mole/1mole
                                                                       = 0.1 moles

Therefore moles of Cu obtained is 0.1 moles

Answer 2

Answer:

Equation: Zn + CuCl₂ ⇒ ZnCl₂ + Cu

= 65g of Zn + 134.5 g of Cucl₂ ⇒ 136g of ZnCl₂ + 63.5g of Cu

∴ Zn = 65, Cu = 63.5, Cl = 35.5

= 1 mole Zn + 1 mole Culc₂ ⇒ 1 mole of Cu

= 2 moles Zn + 0.1 mole Cucl₂ ⇒ ?

= 2 x 65 + 0.1 x 134.5 ⇒ 'X'g of Cu

= 130g of Zn + 13.45g of Cucl₂ ⇒ 'X'g of Cu

= 134.5g of Cucl₂ ⇒ 63.5g of Cu

= 13.45g of Cucl₂ ⇒ ?

= 13.45/134.5 x 63.5 = 6.35g = 0.1 mole

⇒ 0.1 mole Cu is obtained from 2 moles of Zn and 6.023 x 10²² formula units of CuCl₂