Understanding Stoichiometry

What is stoichiometry and why is it important in chemistry?

• Stoichiometry is the study of chemical bonding.

• Stoichiometry focuses on the color changes in reactions.

• Stoichiometry is the study of the quantitative relationships in chemical reactions, crucial for predicting reactant and product amounts.

• Stoichiometry is only relevant for gases in reactions.

Define the law of conservation of mass in the context of stoichiometry.

• Mass can be converted into energy during a reaction.

• The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction.

• The total mass of products is always less than the reactants.

• Mass can be created in a chemical reaction.

How do you balance a chemical equation? Provide an example.

• C3H8 + 4 O2 -> 3 CO2 + 5 H2O

• C3H8 + 2 O2 -> CO2 + H2O

• For example, to balance the equation for the combustion of propane: C3H8 + 5 O2 -> 3 CO2 + 4 H2O.

• C3H8 + 3 O2 -> 2 CO2 + 3 H2O

What is a mole, and how is it used in stoichiometric calculations?

• A mole is equivalent to 1 liter of solution.

• A mole is a type of chemical reaction.

• A mole is a unit representing 6.022 x 10^23 particles, used in stoichiometric calculations to relate amounts in chemical reactions.

• A mole is a measure of temperature in chemistry.

Calculate the number of moles in 50 grams of water (H2O).

• 0.50 moles

• 3.14 moles

• 1.25 moles

• 2.77 moles

If 2 moles of hydrogen react with 1 mole of oxygen, how many moles of water are produced?

• 1 mole of water

• 3 moles of water

• 2 moles of oxygen

• 2 moles of water

Explain the concept of limiting reactants with an example.

• In the reaction 2H2 + O2 -> 2H2O, O2 is the excess reactant when 4 moles of H2 and 1 mole of O2 are present.

• In the reaction 2H2 + O2 -> 2H2O, O2 is the limiting reactant when 3 moles of H2 and 1 mole of O2 are present.

• In the reaction 2H2 + O2 -> 2H2O, both H2 and O2 are limiting reactants when 1 mole of each is present.

• In the reaction 2H2 + O2 -> 2H2O, H2 is the limiting reactant when 2 moles of H2 and 2 moles of O2 are present.

How do you determine the percent yield of a reaction?

• Percent Yield = (Theoretical Yield / Actual Yield) x 100%

• Percent Yield = (Actual Yield / Theoretical Yield) x 100%

• Percent Yield = (Actual Yield - Theoretical Yield) x 100%

• Percent Yield = (Actual Yield + Theoretical Yield) x 100%

What is the difference between empirical and molecular formulas?

• Empirical formulas show actual counts; molecular formulas show ratios.

• Molecular formulas are always simpler than empirical formulas.

• Empirical formulas are used only for gases, while molecular formulas are for solids.

• Empirical formulas show ratios; molecular formulas show actual counts.

Provide a stoichiometric calculation for the combustion of propane (C3H8).

• C3H8 + 5 O2 -> 3 CO2 + 4 H2O

• C3H8 + 3 O2 -> 2 CO2 + 2 H2O

• C3H8 + 4 O2 -> 3 CO2 + 5 H2O

• C3H8 + 6 O2 -> 4 CO2 + 3 H2O