Hydrogen peroxide is used as a cleaning agent in the...

Hydrogen peroxide is used as a cleaning agent in the treatment of cuts and abrasions for several reasons. It is an oxidizing agent that can directly kill many microorganisms; it decomposes upon contact with blood, releasing elemental oxygen gas (which inhibits the growth of anaerobic microorganisms); and it foams upon contact with blood, which provides a cleansing action. In the laboratory, small quantities of hydrogen peroxide can be prepared by the action of an acid on an alkaline earth metal peroxide, such as barium peroxide: $$\mathrm{BaO}_{2}(s)+2 \mathrm{HCl}(a q) \longrightarrow \mathrm{H}_{2} \mathrm{O}_{2}(a q)+\mathrm{BaCl}_{2}(a q)$$ What mass of hydrogen peroxide can result when $1.50 \mathrm{~g}$ barium peroxide is treated with $25.0 \mathrm{~mL}$ hydrochloric acid solution containing $0.0272 \mathrm{~g} \mathrm{HCl}$ per $\mathrm{mL}$ ? What mass of which reagent is left unreacted?

Hydrogen peroxide is used as a cleaning agent in the treatment of cuts and abrasions for several reasons. It is an oxidizing agent that can directly kill many microorganisms; it decomposes upon contact with blood, releasing elemental oxygen gas (which inhibits the growth of anaerobic microorganisms); and it foams upon contact with blood, which provides a cleansing action. In the laboratory, small quantities of hydrogen peroxide can be prepared by the action of an acid on an alkaline earth metal peroxide, such as barium peroxide:
$$\mathrm{BaO}_{2}(s)+2 \mathrm{HCl}(a q) \longrightarrow \mathrm{H}_{2} \mathrm{O}_{2}(a q)+\mathrm{BaCl}_{2}(a q)$$
What mass of hydrogen peroxide can result when $1.50 \mathrm{~g}$ barium peroxide is treated with $25.0 \mathrm{~mL}$ hydrochloric acid solution containing $0.0272 \mathrm{~g} \mathrm{HCl}$ per $\mathrm{mL}$ ? What mass of which reagent is left unreacted?

Key Concepts

Stoichiometry

Stoichiometry involves using the quantitative relationships in a balanced chemical equation to determine the amounts of reactants consumed and products formed. In this context, it ensures that the proportions of barium peroxide, hydrochloric acid, and hydrogen peroxide are correctly applied when calculating how much product can be made based on the masses and volumes provided.

Limiting Reagent

The concept of the limiting reagent refers to the reactant that is completely consumed first in a chemical reaction, thereby determining the maximum amount of product that can be produced. Identifying the limiting reagent is essential because it directly controls the yield of hydrogen peroxide formed from the reaction between barium peroxide and hydrochloric acid.

Solution Concentration

Solution concentration, often expressed as mass per volume or molarity, is used to determine the number of moles of a solute present in a given volume of solution. In the problem, the concentration of hydrochloric acid is provided, which is necessary to calculate the total amount of acid available to react with barium peroxide.

Excess Reagent Calculation

Excess reagent calculation is the process of determining the amount of reactant that remains unreacted after the completion of a chemical reaction. Once the limiting reagent has been identified and the theoretical yield of the product is calculated, the difference between the initial amount and the amount that reacted shows the mass of the reagent left over.

Molar Mass Calculations

Molar mass calculations are critical for converting between the mass of a substance and the number of moles it represents. This conversion is fundamental in stoichiometric analyses, as it allows one to compare the actual amounts of reactants (such as barium peroxide and hydrochloric acid) on a molecular level to assess which one limits the reaction.

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