30cm³ of 2.0M hydrochloric acid completely reacts with 5.0g of impure zinc carbonate. Calculate the per centage purity of zinc carbonate. (Zn=65, C=12, O=16)
Step III
Use mole ratio from the equation in step I
work out the mole of ZnCo used.
ZnCo : Hcl
   1 : 2

Since the number of moles of Hcl is

=

Then, the number of moles of ZnCo₃ is