WorksheetsLimiting and Excess Reactants - Practice Problems
Total questions: 15
Worksheet time: 38mins
1-9.
Answer the questions below after watching the video
What is the purpose of identifying a limiting reactant in a chemical reaction?
To measure the speed of the reaction
To identify the reactant with the highest molar mass
To calculate the total mass of the reactants
To determine which reactant will be completely used up first
How many moles of oxygen are required to completely react with 7.8 moles of magnesium?
3.9 moles
7.8 moles
15.6 moles
1.95 moles
Which reactant is the limiting reactant when reacting 7.8 moles of magnesium with 4.7 moles of oxygen?
None, they are in perfect stoichiometric amounts
Magnesium Oxide (MgO)
Magnesium (Mg)
Oxygen (O2)
Why do we use stoichiometry in limiting reactant problems?
To calculate the energy released
To determine the reactants' molar ratios
To balance the chemical equation
To identify the physical states of reactants
What role does the conversion factor play in these calculations?
It measures the reaction rate
It shows the molar ratio between reactants and products
It converts grams to moles
It determines the reaction's temperature
What is the maximum amount of magnesium oxide (MgO) that can be produced from 7.8 moles of magnesium?
9.4 moles
15.6 moles
3.9 moles
7.8 moles
How many moles of oxygen will be left over as the excess reactant?
0.8 moles
0 moles
1.6 moles
3.9 moles
What happens to the excess reactant in a chemical reaction?
It disappears without a trace
It is completely used up
It the limiting reagent remains unchanged
A portion of it remains unreacted
After identifying the limiting reactant, what is the next step?
Calculate the amount of product formed
Calculate the total mass of reactants
Determine the reaction rate
Measure the temperature change
a. Mg + 2HCl --> MgCl2 + H2
If you start with 100 grams of CaCO3 and 50 grams of HCl in the reaction CaCO3+2HCl→CaCl2+CO2+H2O , which is the limiting reactant? (Molar mass of CaCO3 = 100 g/mol, Molar mass of HCl = 36.5 g/mol)
CaCO3
HCl
Neither, as they react in exact stoichiometric amounts
It cannot be determined without more information
If 5.0 grams of A react with 3.0 grams of B to produce C, and after the reaction, there are still 1.0 grams of B left, which is the limiting reagent?
A
B
C
Both A and B
2C + 1M + G2 → C2MG2. If you have 5 Marshmallows (M), 9 Chocolate Pieces (C), and 9 Graham Cracker Halves (G), how many S'mores can you make?
If 4 moles of A react with 5 moles of B to produce 3 moles of C , what is the theoretical yield of C in grams if the molar mass of C is 60 g/mol?
60 grams
120 grams
180 grams
240 grams
What is the theoretical yield of H2O in grams when 16 grams of O2 react with excess H2 according to the equation 2H2+O2→2H2O ? (Molar mass of H2O = 18 g/mol)
18 grams
36 grams
72 grams
144 grams
