[Nikky Wong]

Smithsonite(or zinc carbonate) is a mineral ore of zinc. It reacts with nitric acid to give a salt A which can be used to set dyes on fabrics in the dyeing industry. The procedures for preparing the salt A from Smithsonite are as follows:
Stage 1 : Dissolve small portions of powdered Smithsonite in 100.0cm³ of 1.0M nitric acid in a beaker with constant stirring, until it is in excess.
Stage 2 : Filter the solution from Stage 1 to get a clear solution of salt A.
Stage 3 : Evaporate the filtrate from Stage 2 to obtain the crystals of salt A.

Questions:
(a) Name salt A. [is it zinc nitrate?]
(b) Write a chemical equation for the reaction between Smithsonite and nitric acid.
[is it : ZnCo₃(aq)+2HNO₃→Zn(NO₃)₂(aq)+CO₂(g)+H₂O(l) ?]
(c) State TWO obsercations indicating the powdered Smithsonite added is in excess.
(d) Why is it necessary to have Smithsonite added in excess?
(e) Draw a labelled diagram to show how to obtain the filtrate in Stage 2.
(f) Calculate the theoretical mass of anhydrous salt A that can be obtained.
(Relative atomic masses: N=14.0, O=16.0, Zn=65.4)

Thanks!

[Dan]

Smithsonite(or zinc carbonate) is a mineral ore of zinc. It reacts with nitric acid to give a salt A which can be used to set dyes on fabrics in the dyeing industry. The procedures for preparing the salt A from Smithsonite are as follows:
Stage 1 : Dissolve small portions of powdered Smithsonite in 100.0cm³ of 1.0M nitric acid in a beaker with constant stirring, until it is in excess.
Stage 2 : Filter the solution from Stage 1 to get a clear solution of salt A.
Stage 3 : Evaporate the filtrate from Stage 2 to obtain the crystals of salt A.

Questions:
(a) Name salt A. [is it zinc nitrate?]
(b) Write a chemical equation for the reaction between Smithsonite and nitric acid.
[is it : ZnCo₃(aq)+2HNO₃→Zn(NO₃)₂(aq)+CO₂(g)+H₂O(l) ?]
(c) State TWO obsercations indicating the powdered Smithsonite added is in excess.
(d) Why is it necessary to have Smithsonite added in excess?
(e) Draw a labelled diagram to show how to obtain the filtrate in Stage 2.
(f) Calculate the theoretical mass of anhydrous salt A that can be obtained.
(Relative atomic masses: N=14.0, O=16.0, Zn=65.4)

Thanks!

(a) Agreed.
(b) Looks fine assuming ZnCo₃ is just a typo (there is no cobalt in here).
(c) When the smithsonite is in excess, the reaction will stop (because all the nitric acid is consumed). Based on your chemical equations, what do you expect to observe when the reaction happens? These things will stop happening when the reaction is complete.
(d) If you do not use smithsonite in excess, what will be in your flask after stage 3? (look at the chemical equation)
(e) How do you obtain filter coffee from ground coffee beans? It's basically the same thing.
(f) Google yield calculation.

[Nikky Wong]

about part b, I think I have typed it wrongly, it should be:  ZnCO3(aq)+2HNO3→Zn(NO3)2(aq)+CO2(g)+H2O(l)

about part c, the observations are the reaction between the powdered Smithsonite and the nitric aicd, aren't they? I wrote: 1.many colourless gas bubbles are given out 2.The zinc carbonate dissolves.

about part d, that means if we don't use Smithsonite in excess, we cannot evaporate the filtrate, is it?

about part e, I got it. I drew a labelled diagram and please check the attach. I am not sure it's correct or wrong.

about part f, what do you mean? Would you kindly explain?

Thank you

[Dan]

about part b, I think I have typed it wrongly, it should be:  ZnCO3(aq)+2HNO3→Zn(NO3)2(aq)+CO2(g)+H2O(l)

Is ZnCO₃ really (aq)? Check state symbols

about part c, the observations are the reaction between the powdered Smithsonite and the nitric aicd, aren't they? I wrote: 1.many colourless gas bubbles are given out 2.The zinc carbonate dissolves.

You will observe these things when the the reaction is happening. The reaction stops when one (or more) of the reagents is completely consumed. If the mineral is in excess, all the nitric acid will be consumed so the mixture will stop bubbling and the  mineral will stop dissolving.

about part d, that means if we don't use Smithsonite in excess, we cannot evaporate the filtrate, is it?

If you do not use smithsonite in excess, what will be in your flask after stage 3?

about part e, I got it. I drew a labelled diagram and please check the attach. I am not sure it's correct or wrong.

Looks sensible to me

about part f, what do you mean? Would you kindly explain?

Explanations/tutorials on yield calculation are widely available online, have a look and then attempt the question - click here.

[Nikky Wong]

umm...it should be ZnCO₃(s).

thank you very much, you have helped me a lot:)