Federal regulations set an upper limit of 50 parts per million (ppm) of NH₃ in the air in a work environment [that is, 50 molecules of NH₃(g) for every million molecules in the air]. Air from a manufacturing operation was drawn through a solution containing 1.00⨉10² mL of 0.0105 M HCl. The NH₃ reacts with HCl according to: NH₃₍aq) + HCl(aq) → NH₄Cl(aq). After drawing air through the acid solution for 10.0 min at a rate of 10.0 L/min, the acid was titrated. The remaining acid needed 13.1 mL of 0.0588 M NaOH to reach the equivalence point. (a) How many grams of NH₃ were drawn into the acid solution?

검증된 단계별 안내

Calculate the total volume of air drawn through the solution: \(10.0 \text{ L/min} \times 10.0 \text{ min} = 100.0 \text{ L}\).

Determine the initial moles of HCl in the solution: \(0.0105 \text{ M} \times 0.100 \text{ L} = 0.00105 \text{ mol HCl}\).

Calculate the moles of NaOH used in the titration: \(0.0588 \text{ M} \times 0.0131 \text{ L} = 0.00076968 \text{ mol NaOH}\).

Determine the moles of HCl that reacted with NH\(_3\) by subtracting the moles of NaOH from the initial moles of HCl: \(0.00105 \text{ mol} - 0.00076968 \text{ mol} = 0.00028032 \text{ mol HCl reacted}\).

Convert the moles of NH\(_3\) to grams using the molar mass of NH\(_3\) (17.03 g/mol): \(0.00028032 \text{ mol} \times 17.03 \text{ g/mol}\).

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions based on the balanced chemical equation. It allows us to determine the amount of substances consumed or produced in a reaction. In this case, understanding the stoichiometric relationship between NH3 and HCl is crucial for calculating how much NH3 reacted with the acid.

Molarity and Dilution

Molarity (M) is a measure of concentration defined as moles of solute per liter of solution. In this problem, the concentration of HCl is given, and we need to use it to find the number of moles of HCl that reacted. Additionally, the dilution of HCl after the reaction with NH3 will be important for determining how much acid remains, which can be used to find the amount of NH3 that was absorbed.

Titration

Titration is a laboratory technique used to determine the concentration of a solute in a solution by reacting it with a reagent of known concentration. In this scenario, the remaining HCl after the reaction with NH3 is titrated with NaOH to find out how much HCl was left, which helps in calculating the amount of NH3 that reacted. The equivalence point in titration indicates that the amount of titrant added is stoichiometrically equivalent to the amount of substance being analyzed.

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교과서 질문

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교과서 질문

Potassium superoxide, KO₂, is often used in oxygen masks (such as those used by firefighters) because KO₂ reacts with CO₂ to release molecular oxygen. Experiments indicate that 2 mol of KO₂(s) react with each mole of CO₂(g). (b) Indicate the oxidation number for each atom involved in the reaction in part (a). What elements are being oxidized and reduced?

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교과서 질문

Federal regulations set an upper limit of 50 parts per million (ppm) of NH₃ in the air in a work environment [that is, 50 molecules of NH₃(g) for every million molecules in the air]. Air from a manufacturing operation was drawn through a solution containing 1.00⨉10² mL of 0.0105 M HCl. The NH₃ reacts with HCl according to: NH₃₍aq) + HCl(aq) → NH₄Cl(aq). After drawing air through the acid solution for 10.0 min at a rate of 10.0 L/min, the acid was titrated. The remaining acid needed 13.1 mL of 0.0588 M NaOH to reach the equivalence point. (b) How many ppm of NH₃ were in the air? (Air has a density of 1.20 g/L and an average molar mass of 29.0 g/mol under the conditions of the experiment.)

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