Chapter 15: Problem 14
Bromine and chlorine react to produce bromine monochloride according to the equation \\[ \mathrm{Br}_{2}(\mathrm{g})+\mathrm{Cl}_{2}(\mathrm{g}) \rightleftharpoons 2 \mathrm{BrCl}(\mathrm{g}) \\] \(0.2 \mathrm{mol}\) of bromine gas and \(0.2 \mathrm{mol}\) of chlorine gas are introduced into a sealed flask with a volume of \(5.0 \mathrm{dm}^{3}\). Under the conditions of the experiment, \(K=36.0 .\) How much BrCl will be present at equilibrium? (Section 15.4 )
Short Answer
Step by step solution
Write the Expression for Equilibrium Constant
Calculate Initial Concentrations
Set Up the Change in Concentration
Write Equilibrium Concentrations in Terms of x
Substitute into Equilibrium Expression
Solve for x
Determine Equilibrium Concentration of BrCl
Unlock Step-by-Step Solutions & Ace Your Exams!
-
Full Textbook Solutions
Get detailed explanations and key concepts
-
Unlimited Al creation
Al flashcards, explanations, exams and more...
-
Ads-free access
To over 500 millions flashcards
-
Money-back guarantee
We refund you if you fail your exam.
Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Equilibrium Constant
- The equilibrium constant is derived from the concentrations of the products raised to their stoichiometric coefficients divided by the concentrations of reactants raised to their stoichiometric coefficients.
- For the reaction \( \mathrm{Br}_{2} + \mathrm{Cl}_{2} \rightleftharpoons 2 \mathrm{BrCl} \), the expression for \( K \) is given by \[ K = \frac{{[\mathrm{BrCl}]^2}}{{[\mathrm{Br}_2][\mathrm{Cl}_2]}}. \]
- The value of \( K \), which is \( 36.0 \) in this case, helps us predict how far the reaction will proceed to produce \( \mathrm{BrCl} \).
Concentration Calculation
- Initially, we have 0.2 moles of \( \mathrm{Br}_2 \) and \( \mathrm{Cl}_2 \) each, introduced into a 5.0 dm³ flask. The initial concentration \( [\mathrm{Br}_2]_0 \) and \( [\mathrm{Cl}_2]_0 \) is calculated by dividing the moles by the volume of the flask:
- \[ [\mathrm{Br}_2]_0 = [\mathrm{Cl}_2]_0 = \frac{0.2 \text{ mol}}{5.0 \text{ L}} = 0.04 \text{ M}. \]
- This step sets the stage for the changes that occur as the reaction moves toward equilibrium.
Reaction Stoichiometry
- The balanced reaction \( \mathrm{Br}_{2} + \mathrm{Cl}_{2} \rightleftharpoons 2 \mathrm{BrCl} \) indicates that one mole of \( \mathrm{Br}_{2} \) reacts with one mole of \( \mathrm{Cl}_{2} \) to produce two moles of \( \mathrm{BrCl} \).
- When approaching equilibrium, a change \( x \) occurs where \( \mathrm{Br}_{2} \) and \( \mathrm{Cl}_{2} \) concentrations decrease by \( x \), while \( \mathrm{BrCl} \) increases by \( 2x \).
- The stoichiometric coefficients guide us in setting up these change relationships as: \[ [\mathrm{Br}_2] = 0.04 - x, \]\[ [\mathrm{Cl}_2] = 0.04 - x, \]\[ [\mathrm{BrCl}] = 2x. \]
Quadratic Equation
- We use the equilibrium expression and the known value of \( K \) to set up a quadratic equation as follows:
- The relationship \[ K = \frac{(2x)^2}{(0.04 - x)^2} \] leads to \[ 4x^2 = 36(0.04 - x)^2. \]
- Expanding and rearranging gives a quadratic equation: \[ 0 = 32x^2 - 2.88x + 0.0576. \]
- The quadratic formula \( x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \) is then used to find \( x \), the change in concentration.