May 14th, 2018, 03:05 AM  #1 
Member Joined: May 2015 From: Australia Posts: 77 Thanks: 7  stoichiometry equation 1: 2ZnS + 2O2 > 2ZnO + SO2 equation 2: ZnO + CO > Zn + CO2 300 tons of ZnS are processed each month by the plant. only 95% of the ZnO can be converted to Zn. Calculate the mass of Zinc produced in one month. 0.95 x 300 tons ZnS = 285 tons ZnS n(ZnS) = m/M = 285,000,000g / 97.44g/mol = 2924877mol Since ZnS:ZnO is 2:2, n(ZnO)=2924977mol ZnO(eqn1):ZnO(eqn2) 2:1 Therefore, n(ZnO(eqn2))=1462438mol ZnO:Zn 1:1 n(Zn)=1462438mol m(Zn)= n x Mr = 95614224g = 95.6 tonnes Is that correct? part b) the plant burns hexene in an undersupply of oxygen to produce CO required: Equation 3: C6H12 + 6O2 > 6CO + 6H2O What mass of hexene is required on a daily basis for the conversion of 10 tons of ZnO? n(ZnO) = m/Mr = 100,000,00g / 81.38g/mol = 122880mol ZnO:CO 1:1 n(CO) = 122880 mol CO(eqn2):CO(eqn3) 1:6 n(CO(eqn3))= 737282 mol C6H12:CO 1:6 n(C6H12) = 737282/6 = 122880mol m(C6H12) = n x Mr = 122880 x 84.156 = 10341089g = 10.3 tonnes I'm not sure if my solutions are correct. 
May 14th, 2018, 06:38 AM  #2 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 13,964 Thanks: 991 
Don't think I've ever seen such confusing variables and equations!

May 14th, 2018, 07:16 AM  #3  
Math Team Joined: May 2013 From: The Astral plane Posts: 2,041 Thanks: 815 Math Focus: Wibbly wobbly timeywimey stuff.  Quote:
Here's a start: First change 300 tons to metric (ie. grams). $\displaystyle 300 \text{ tons ZnS} = 2.72155 \times 10^{8} \text{ g ZnS}$. So $\displaystyle \frac{2.72155 \times 10^{8} \text{ g ZnS}}{1} \cdot \frac{1 \text{ mol ZnS}}{97.44 \text{ g ZnS}} \cdot \frac{2 \text{ mol ZnO}}{2 \text{ mol ZnS}} = 2.7931 \times 10^6 \text{ mol ZnO}$ So you can produce $\displaystyle 95 \% \cdot 2.7931 \times 10^6 \text{ mol ZnO} = 2.6954 \times 10^6 \text{ mol ZnO}$ The second step is done the same way. Can you finish? Dan Last edited by skipjack; May 14th, 2018 at 08:49 AM.  
May 14th, 2018, 08:57 AM  #4 
Global Moderator Joined: Dec 2006 Posts: 20,288 Thanks: 1968 
Was 2ZnS + 3O$_2$ > 2ZnO + 2SO$_2$ intended? If "300 tons of ZnS" is correct, shouldn't the answer be given in tons rather than tonnes? Was "10 tons of ZnO" intended to be "10 tonnes of ZnO"? 
May 14th, 2018, 11:22 AM  #5  
Senior Member Joined: Jun 2015 From: England Posts: 891 Thanks: 269  Quote:
Why not just work in tonmolecules? The unit of weight is irrelevant.  
May 14th, 2018, 11:38 AM  #6  
Math Team Joined: May 2013 From: The Astral plane Posts: 2,041 Thanks: 815 Math Focus: Wibbly wobbly timeywimey stuff.  Quote:
And yes, if the problem is given in tons then the answer should be also. Thanks for the correction. Dan  

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