Stoichiometry, % yield, Limiting Reactants

In the reaction 2H2 + O2 → 2H2O, if you start with 4 moles of H2 and 2 moles of O2, which is the limiting reactant?

• H2 is the limiting reactant because it will be completely consumed first.

• O2 is the limiting reactant because it will be completely consumed first.

• Both H2 and O2 are limiting reactants.

• There is no limiting reactant in this reaction.

What is the formula for calculating percent yield?

• Percent yield = (actual yield / theoretical yield) x 100%

• Percent yield = (theoretical yield / actual yield) x 100%

• Percent yield = (actual yield + theoretical yield) x 100%

• Percent yield = (actual yield - theoretical yield) x 100%

What is stoichiometry?

• A branch of chemistry that deals with the calculation of reactants and products in chemical reactions based on the conservation of mass.

• A method for measuring the temperature of chemical reactions.

• A technique used to separate mixtures into their individual components.

• A study of the physical properties of elements and compounds.

Define limiting reactant.

• The reactant that is present in excess in a chemical reaction.

• The substance that is completely consumed in a chemical reaction, limiting the amount of product that can be formed.

• The reactant that determines the rate of the reaction.

• The product that is formed in the largest quantity.

How do you identify the limiting reactant in a reaction?

• By calculating the moles of each reactant and determining which one produces the least amount of product.

• By identifying the reactant with the highest molecular weight.

• By measuring the temperature change during the reaction.

• By adding excess of one reactant to see which one runs out first.

How do you convert grams to moles?

• Multiply the mass of the substance by its molar mass.

• Add the mass of the substance to its molar mass.

• Divide the mass of the substance by its molar mass.

• Subtract the molar mass from the mass of the substance.

If you have 10 moles of A and 15 moles of B in the reaction A + 2B → C, how many moles of C can be produced?

• 3 moles of C

• 5 moles of C

• 7 moles of C

• 10 moles of C

What is percent yield?

• A measure of the total amount of product produced in a reaction.

• A measure of the efficiency of a reaction, calculated as (actual yield / theoretical yield) x 100%.

• The ratio of the actual yield to the maximum possible yield, expressed as a fraction.

• A calculation used to determine the purity of a substance.

If 10g of a reactant produces 8g of product, what is the percent yield?

• 70%

• 75%

• 80%

• 85%

What is the significance of the coefficients in a balanced chemical equation?

• They indicate the temperature at which the reaction occurs.

• They represent the physical state of the reactants and products.

• They indicate the ratio of moles of reactants and products involved in the reaction.

• They show the energy changes during the reaction.