Vocabulary
Define "excess reactant".
the reactant of which you have more than you need for a reaction to occur
Theoretical yield calculations are based off the ____________ reactant.
limiting
Given: 2 H2 + O2 -> 2 H2O
How many grams of H2O are produced when 2.50 mol O2 are reacted with excess H2?
90.1 g H2O
Given: Na + Br2 → NaBr
Find the limiting reactant if you combine 5.75 mol Na and 3.4 mol Br2 based on the unbalanced equation above.
Limiting reactant is Na
What is the mole ratio between hydrogen gas and oxygen gas in 2 H2 + O2 -> 2 H2O?
2 H2 : 1 O2
Define "limiting reactant".
the reactant which you "run out of" first, before the excess reactant
Write one math equation to describe how to find percent yield.
% yield = (actual product / theoretical product) * 100 %
Given: 2 KClO3 -> 2 KCl + 3 O2
If your theoretical yield is 80.0 grams of O2, how many moles of KClO3 do you need to decompose (assuming a 100 % yield)?
1.67 mol KClO3
Given: HgO -> Hg+O2
In the unbalanced equation above, how many moles of mercury are produced if 24.5 moles of mercury(II) oxide decompose?
Balanced: 2 HgO -> 2 Hg+ O2
24.5 mol HgO
What nomenclature type does MgF2 belong to AND what is the proper IUPAC name for this compound?
Type I nomenclature
magnesium fluoride
What is a mole ratio?
The ratio between substances in a chemical equation (represented by coefficients)
Provide at least one reason why a percent yield might appear to be greater than 100 %.
Examples: miscalculation, mismeasurement, contamination, etc.
Given: Mg + 2 NaF -> MgF2 + 2 Na
If you react 5.5 g NaF with excess Mg, how many moles of MgF2 will be produced?
0.065 mol MgF2
Given: Cu + AgNO3 -> Cu(NO3)2 + Ag
In the unbalanced equation above, how many moles of Cu are needed to react completely with 3.50 moles of AgNO3?
Balanced: Cu + 2 AgNO3 -> Cu(NO3)2 + 2 Ag
1.75 mol Cu
List three types of evidences of chemical changes.
Any three will work.
Define "theoretical yield".
the amount of a product that you should obtain from a reaction
Provide at least two reasons why a percent yield might be less than 100 %.
Your answer cannot be along the lines of "the person miscalculated".
Example: product lost in transfer, spillage, evaporation, side reactions, etc.
Given: LiOH + HBr ->LiBr + H2O
If you react 10.0 grams of LiOH with excess HBr, how many grams of LiBr should be produced?
36.3 g LiBr
Given: 6 Na + Fe2O3 -> 3 Na2O + 2 Fe
If 100.0 g of Na and 100.0 g of Fe2O3 are combined, determine the limiting reagent.
100.0 g Na * (mol / 22.99 g) = 4.350 mol Na
100.0 g Fe2O3 * (mol / 159.69 g) = 0.6262 mol Fe2O3
0.6262 mol Fe2O3 * (6 mol Na / mol Fe2O3) = 3.757 mol Na
Fe2O3 is LR
Contrast "liquid" and "aqueous".
Liquid is the pure substance melted. Aqueous is a substance dissolved in water.
Define "stoichiometry".
the relationship between amounts of substances in a chemical reaction
Describe how to find theoretical yield.
Find the limiting reactant, then use the mole ratio between the limiting reactant and the product to convert to theoretical yield.
Pentane (C5H12) reacts with oxygen gas to produce carbon dioxide and water.
How many grams of carbon dioxide will be produced by the reaction of 108.0 grams of pentane with excess oxygen?
C5H12 + 8 O2 -> 5 CO2 + 6 H2O
108.0 g C5H12 * (mol C5H12 / 72.15 g) * (5 mol CO2 / mol C5H12) * (44.01 g CO2 / mol) = 329.4 g CO2
Given: C2H5NH2 + O2 → CO2 + N2 + H2O
5.00 mol C2H5NH2 reacts with excess oxygen in the unbalanced equation above. If the percent yield for this reaction is 50.6%, how much CO2 was produced (in mol)?
Balanced: 2 C2H5NH2 + 7 O2 → 4 CO2 + N2 + 6 H2O
5.00 mol C2H5NH2 * (4 mol CO2 / 2 mol C2H5NH2) = 10.0 mol CO2 theoretically
50.6 % = (actual / 10.0 mol) * 100 %, therefore 5.06 mol actually produced
Balance the following equation.
PCl5 + H2O -> H3PO4 + HCl
PCl5 + 4 H2O -> H3PO4 + 5 HCl