At one time, a common means of forming small quantities of oxygen gas in the laboratory was to heat KClO₃: 2 KClO₃(s) → 2 KCl(s) + 3 O₂(g) ΔH = -89.4 kJ For this reaction, calculate H for the formation of (b) 10.4 g of KCl.

검증된 단계별 안내

Identify the molar mass of KCl by adding the atomic masses of K (potassium) and Cl (chlorine).

Calculate the number of moles of KCl in 10.4 g using the formula: \( \text{moles of KCl} = \frac{\text{mass of KCl}}{\text{molar mass of KCl}} \).

Use the stoichiometry of the balanced chemical equation to determine the relationship between moles of KCl and the enthalpy change (\( \Delta H \)).

Calculate the enthalpy change for the formation of the calculated moles of KCl using the relationship: \( \Delta H = \text{moles of KCl} \times \frac{-89.4 \text{ kJ}}{2 \text{ moles of KCl}} \).

Express the final enthalpy change in kJ for the formation of 10.4 g of KCl.

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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 equation. It allows us to determine the relationships between the amounts of substances involved in a reaction, such as how many grams of a product can be formed from a given mass of reactants. In this case, stoichiometry will help us relate the mass of KCl produced to the amount of KClO3 reacted.

Enthalpy Change (ΔH)

Enthalpy change (ΔH) is a measure of the heat energy absorbed or released during a chemical reaction at constant pressure. In the given reaction, ΔH = -89.4 kJ indicates that the reaction is exothermic, meaning it releases energy. Understanding ΔH is crucial for calculating the energy associated with the formation of products, such as KCl, from the reactants.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is essential for converting between the mass of a substance and the number of moles, which is necessary for stoichiometric calculations. To find the amount of KCl formed, we need to know its molar mass to convert the given mass (10.4 g) into moles for further calculations.

At one time, a common means of forming small quantities of oxygen gas in the laboratory was to heat KClO3: 2 KClO3(s) → 2 KCl(s) + 3 O2(g) ΔH = -89.4 kJ For this reaction, calculate H for the formation of (b) 10.4 g of KCl.