1) When 8 liters of hydrogen sulfide gas
react with 2.43 mol of zinc, what mass of
zinc sulfide can be formed?
If a student goes to lab and gets a 65.2%
yield, how many grams of zinc sulfide did
they actually retrieve in lab?
HINT: balanced equation, limiting reagent,
2 parallel equations to evaluate,
% yield = (AY/TY)100
2) When a single replacement reaction
occurs, and one metal replaces another, the
metal that is produced is in _______ form
(think lab).
The reactant that gets used up first in a
chemical reaction is the ________ reagent.
3) In lab, you witnessed a single
replacement reaction between iron and
copper (II) sulfate. How many atoms of iron
must react with sufficient copper (II) sulfate
to produce 165.4 g of copper metal?
Assume the iron takes a +2 form when
bonded.
HINT: Since you have more than one substance, a
balanced equation with correct formulas is needed.
You’ll also need Avogadro’s number to deal with atoms.
4) 58.2 g of phosphoric acid reacts with 55.5
g of magnesium hydroxide. When this
happens:
a) what is the theoretical yield of
magnesium phosphate?
b) if 70.6 g of magnesium phosphate are
retrieved in lab, what is the percentage
yield?
c) what mass of excess reagent is left
over?
HINT: You have more than one substance
so you need a balanced equation with
correct formulas. Since you are given a
known mass of each reactant, it is a limiting
reagent problem. This means you need two
parallel calculations so that you can compare
the mass of magnesium phosphate possible
from each reactant.
5) Potassium chlorate decomposes to give
potassium chloride and oxygen gas. We saw
this on mole day with the gummy bear
sacrifice. If 13.3 grams of potassium
chlorate decompose, what mass of oxygen
gas is produced?
HINT: You have more than one substance
so you need a balanced chemical equation
that uses the correct formulas.
6) Octane gas, C8H18, burns in the presence
of oxygen. If 2.6 moles of octane burn with
sufficient oxygen at STP, how many liters of
carbon dioxide gas will be produced?
HINT: You have more than one substance
so you need a balanced equation with
correct formulas. Also, since you’re asked
about liters, you’ll need the molar volume
tool.
7) Calcium phosphide is prepared by the reaction
of solid calcium metal and solid phosphorus.
Determine the mass of calcium phosphide that can
be formed if 25 g of calcium combine with 25 g of
phosphorus in the aforementioned reaction. What
mass of excess reagent was used? What mass of
excess reagent was left over?
HINT: You need a balanced equation. There are amounts of each
reactant so you need 2 parallel calculations to determine limiting
reagent. To find amounts of excess reagent used and left, you’ll
need stoichiometry as well as subtraction.