The Grass Doctor

I'm confused in Chemistry???

Urea, a compound in fertilizer, has the chmichal formula CO(NH2)2. What is the percentage composition of this compound? Also.... Which compound has the greater percentage of zinc? Smithsonite, ZnCO3 or Sphalerit, ZnS

Public Comments

1. The first question needs more information. What part of the compound do you need to find the chem. comp. of? Or do you need the fractional abundance? As for the second question, you just divide the molar mass of Zn by the formula mass of the compound. 1 mol Zn = 65.4 g 1 molecule ZnCO3 = 125.41g. 65.4g Zn/ 125.41g ZnCO3 = 0.52 = 52.1% ZnS = 97.46g. 65.4g Zn / 97.46 g ZnS = 0.671 = 67.1 %
2. They want to know the % composition of the individual elements. In your question that would be Carbon, Oxygen, Nitrogen, Hydrogen. You look up the molecular weight of the entire compound and divide the molecular weight of each individual atom over that total.. Hydrogen is in their twice, for NH2, and The entire NH2 molecule is in their twice...so in the end you'll have to multiply N by 2 and H by 4. It should come out in percentages less than 1. Do the same thing for the second part of your problem.
3. For the second question, you want to find the molar mass for each(add up the weights from the periodic table of all the elements in the compound). Then take the weight of zinc and divide into each compound seperately. The number given is the percentage. For the first question, i think there is a component you are leaving out, bc i can't solve it