Reaction of gaseous fluorine with compound X yields a sin- gle product Y, whose mass percent composition is 61.7% F and 38.3% Cl. (c) Calculate ΔH° for the synthesis of Y using the following information: 2 CIF1g2 + O21g2 S Cl2O1g2 + OF21g2 ΔH° = + 205.4 kJ 2 CIF31l2 + 2 O21g2 S Cl2O1g2 + 3 OF21g2 ΔH° = + 532.8 kJ OF21g2 ΔH°f = + 24.5 kJ>mol

Verified step by step guidance

1. Identify the chemical formula of compound Y based on its mass percent composition: 61.7% F and 38.3% Cl. This suggests the formula is ClF3.
2. Write the balanced chemical equation for the formation of ClF3 from its elements: Cl2(g) + 3F2(g) -> 2ClF3(g).
3. Use Hess's Law to calculate the enthalpy change (ΔH°) for the formation of ClF3. This involves manipulating the given reactions to derive the desired reaction.
4. Reverse the first given reaction to express Cl2O and OF2 as reactants, and adjust the enthalpy change accordingly: Cl2O(g) + OF2(g) -> 2ClF(g) + O2(g), ΔH° = -205.4 kJ.
5. Combine the reversed first reaction and the second given reaction to eliminate intermediates and obtain the formation reaction of ClF3. Calculate the overall ΔH° using the enthalpy changes of the manipulated reactions.

Key Concepts

Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions based on the conservation of mass. It involves using balanced chemical equations to determine the relationships between the amounts of substances consumed and produced. Understanding stoichiometry is essential for calculating the quantities needed for reactions and for interpreting the results of chemical equations.

Enthalpy Change (ΔH°)

Enthalpy change (ΔH°) refers to the heat content change during a chemical reaction at constant pressure. It indicates whether a reaction is exothermic (releases heat, ΔH° < 0) or endothermic (absorbs heat, ΔH° > 0). Knowing the enthalpy changes of related reactions allows for the application of Hess's law, which states that the total enthalpy change for a reaction is the sum of the enthalpy changes for individual steps.

Mass Percent Composition

Mass percent composition is a way to express the concentration of an element in a compound as a percentage of the total mass of the compound. It is calculated by dividing the mass of the element by the total mass of the compound and multiplying by 100. This concept is crucial for determining the empirical formula of a compound and for understanding the proportions of elements involved in chemical reactions.