For the reaction H2(g) + I2(g) ⇌ 2 HI(g), Kc = 55.3 at 700 K. In a 2.00-L flask containing an equilibrium mixture of the three gases, there are 0.056 g H2 and 4.36 g I2. What is the mass of HI in the flask?

Verified step by step guidance

Step 1: Convert the mass of H2 and I2 to moles using their molar masses. The molar mass of H2 is approximately 2.02 g/mol, and the molar mass of I2 is approximately 253.8 g/mol.

Step 2: Calculate the concentrations of H2 and I2 in the flask by dividing the number of moles of each gas by the volume of the flask (2.00 L).

Step 3: Use the equilibrium constant expression for the reaction, Kc = [HI]^2 / ([H2][I2]), to set up an equation. Substitute the known values of Kc, [H2], and [I2] into this expression.

Step 4: Solve the equation for [HI], the concentration of HI at equilibrium.

Step 5: Convert the concentration of HI to mass by multiplying the concentration by the volume of the flask and the molar mass of HI (approximately 127.9 g/mol).

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Equilibrium Constant (Kc)

The equilibrium constant, Kc, quantifies the ratio of the concentrations of products to reactants at equilibrium for a given reaction at a specific temperature. For the reaction H2(g) + I2(g) ⇌ 2 HI(g), Kc = [HI]^2 / ([H2][I2]). A higher Kc value indicates a greater concentration of products at equilibrium, which is essential for determining the amounts of substances in the reaction.

Molar Mass and Conversions

To find the mass of HI in the flask, it is crucial to convert the given masses of H2 and I2 into moles using their molar masses (H2: 2.02 g/mol, I2: 253.8 g/mol). This conversion allows for the calculation of the initial concentrations of the reactants, which can then be used to determine the equilibrium concentrations of all species involved in the reaction.

Stoichiometry of the Reaction

Stoichiometry refers to the quantitative relationship between reactants and products in a chemical reaction. In this case, the balanced equation shows that one mole of H2 reacts with one mole of I2 to produce two moles of HI. Understanding this ratio is essential for calculating the amount of HI produced based on the initial amounts of H2 and I2 present in the flask.

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