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 should result when $1.50 \mathrm{~g}$ of barium peroxide is treated with $25.0 \mathrm{~mL}$ of hydrochloric acid solution containing $0.0272 \mathrm{~g}$ of $\mathrm{HCl}$ 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 should result when $1.50 \mathrm{~g}$ of barium peroxide is treated with $25.0 \mathrm{~mL}$ of hydrochloric acid solution containing $0.0272 \mathrm{~g}$ of $\mathrm{HCl}$ per $\mathrm{mL}$ ? What mass of which reagent is left unreacted?

Key Concepts

Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions. It involves using the balanced chemical equation to understand and convert between the amounts (in moles or mass) of substances involved in the reaction, ensuring that the law of conservation of mass is upheld.

Limiting Reagent

The limiting reagent is the reactant that is entirely consumed first in a chemical reaction. This concept is crucial because the amount of product formed is dictated by this reagent. Identifying the limiting reagent helps in predicting the maximum possible yield of the reaction.

Molar Mass and Mass-to-Mole Conversions

Molar mass is the mass of one mole of a substance and is essential for converting between mass and moles. This conversion is fundamental in stoichiometric calculations since chemical equations are balanced in moles, not in grams.

Reaction Yield

Reaction yield refers to the amount of product that can be formed in a chemical reaction, based on the stoichiometry and the limiting reagent. It is calculated by first converting the given masses of reactants to moles, then using the balanced equation to determine the moles of product, and finally converting those moles back to mass.

Excess Reagent and Unreacted Mass

In reactions where one reactant is in excess, the excess reagent remains unreacted after the completion of the chemical process. Calculating the leftover amount of an excess reactant involves determining how much of it was required to fully react with the limiting reagent and then finding the difference from the original amount.