Leader: Sara
Course: Chem 177
Instructor: Bonaccorsi
Supplemental Instruction
Date: 2/5/14
Iowa State University
1) If you begin with 5 moles of Barium and 2 moles of Nitrogen. Which one is
limiting and how much product (in moles) will be obtained?
__3_Ba (s) + _1__N2(g)  _1__Ba3N2 (g)
Worksheet 3d:
Limiting Reagents
5 mole Ba*(1 mol Ba3N2/3 mol Ba) = 1.67 mol Ba3N2
2 mol N2*(1 mol Ba3N2/1 mol N2) = 2 mol N2
Ba is limiting
2) A chemist synthesizes phosphorus trichloride by mixing 10.0 g of white
phosphorus (P4) with 30.0 g of chlorine gas and obtained 31.2 g of liquid
phosphorus trichloride.
a. Write a balanced chemical equation for the above reaction.
1 P4(s) +6 Cl2(g) --> 4 PCl3(l)
b. How much product was produced (in moles)?
10.0g P4 * (mol/124.0g) = .0806 mol P4
30.0 g Cl2 (mol/71.0g) = .423 mol Cl2
.423 mol Cl2 * (4 mol PCl3/6 mol Cl2) = .282 mol PCl3
c. What was the limiting reagent?
Cl2
d. What was the percent yeild?
.282 mol PCl3 * ( 137.5 g PCl3/1mol) = 38.8 g PCl3
Percent yield = 31.2 g / 38.8 g = 80.4%
e. How much of the excess reagent is left over?
.423 mol Cl2 * (1 mol P4/6 mol Cl2) = .0705 mol P4
.0705 mol P4 * (124.0 g P4/mol P4) = 8.74 g P4 used
10.0 g – 8.74 g = 1.3 g P4 left over
3) If you dissolve 5 cubes of sugar in your morning coffee, what is the solvent and
what is the solute. If each cube had .36 moles of sugar, and the glass of coffee is
200 mL what is the molarity?
Solute: sugar
Solvent: coffee
Molarity = .36 moles * 5 / (200mL * (1L/1000mL)
4) Name the following?
Mg3(PO4)2
Magnesium Phosphate
iron (III) sulfate
Fe2(SO4)3
Hydroiodic acid
HI (aq)
SiO2
Silicon Dioxide
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