Math Problem Statement

Suppose a 500mL flask is filled with 1.0 mol of N2 and 1.5 mol of O2. The following reaction becomes possible: N2 + O2 -><- 2NO The equilibrium constant K for this reaction is 3.24 at the temperature of the flask. Calculate the equilibrium molarity of NO. Round your answer to two decimal places.

Solution

Let's solve the problem step-by-step.

Step 1: Write down the balanced chemical equation

N2+O22NO\text{N}_2 + \text{O}_2 \leftrightarrow 2\text{NO}

Step 2: Define the initial conditions

  • Volume of the flask, V=0.5V = 0.5 L
  • Moles of N2\text{N}_2 = 1.0 mol
  • Moles of O2\text{O}_2 = 1.5 mol
  • Equilibrium constant, Kc=3.24K_c = 3.24

Step 3: Initial concentrations

Since the volume of the flask is 0.5 L, we calculate the initial concentrations of N2\text{N}_2 and O2\text{O}_2:

[N2]0=1.0mol0.5L=2.0M[\text{N}_2]_0 = \frac{1.0 \, \text{mol}}{0.5 \, \text{L}} = 2.0 \, \text{M} [O2]0=1.5mol0.5L=3.0M[\text{O}_2]_0 = \frac{1.5 \, \text{mol}}{0.5 \, \text{L}} = 3.0 \, \text{M}

Step 4: Set up the equilibrium expression

Let xx be the change in molarity of N2\text{N}_2 and O2\text{O}_2 that reacts to form 2x2x molarity of NO\text{NO}. The equilibrium concentrations are:

[N2]=2.0x[\text{N}_2] = 2.0 - x [O2]=3.0x[\text{O}_2] = 3.0 - x [NO]=2x[\text{NO}] = 2x

Step 5: Write the equilibrium expression using KcK_c

The equilibrium constant expression is:

[ K_c = \frac{[\text{NO}]^2}{[\text{N}_2][\text{O}_2]} ]

Plugging in the equilibrium concentrations:

3.24=(2x)2(2.0x)(3.0x)3.24 = \frac{(2x)^2}{(2.0 - x)(3.0 - x)}

Step 6: Solve for xx

3.24=4x2(2.0x)(3.0x)3.24 = \frac{4x^2}{(2.0 - x)(3.0 - x)}

Cross-multiply and solve the quadratic equation:

3.24(2.0x)(3.0x)=4x23.24 \cdot (2.0 - x)(3.0 - x) = 4x^2 3.24(6.05x+x2)=4x23.24 \cdot (6.0 - 5x + x^2) = 4x^2 19.4416.2x+3.24x2=4x219.44 - 16.2x + 3.24x^2 = 4x^2

Combine like terms:

19.4416.2x0.76x2=019.44 - 16.2x - 0.76x^2 = 0

Rearrange into standard quadratic form:

0.76x2+16.2x19.44=00.76x^2 + 16.2x - 19.44 = 0

Step 7: Solve the quadratic equation

Using the quadratic formula:

x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

Substituting a=0.76a = 0.76, b=16.2b = -16.2, and c=19.44c = -19.44:

x=(16.2)±(16.2)240.76(19.44)20.76x = \frac{-(-16.2) \pm \sqrt{(-16.2)^2 - 4 \cdot 0.76 \cdot (-19.44)}}{2 \cdot 0.76}

Step 8: Calculate the values

Solving this gives:

x1.11x \approx 1.11

Step 9: Determine the equilibrium concentration of NO

[NO]=2x=2×1.11=2.22M[\text{NO}] = 2x = 2 \times 1.11 = 2.22 \, \text{M}

Therefore, the equilibrium molarity of NO\text{NO} is 2.22 M.

Would you like more details or have any questions?

Related Questions

  1. How would the equilibrium shift if the temperature were increased?
  2. What would happen to the equilibrium concentration of NO\text{NO} if more O2\text{O}_2 were added initially?
  3. How does the value of the equilibrium constant KcK_c change with temperature?
  4. What are the units of KcK_c in this reaction, and why?
  5. How do you use the ICE (Initial, Change, Equilibrium) table to find equilibrium concentrations?

Tip

Always check if your quadratic equation solution makes sense by substituting the value back into the equilibrium expression to verify accuracy.

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Math Problem Analysis

Mathematical Concepts

Chemical Equilibrium
Quadratic Equations
Stoichiometry

Formulas

Equilibrium constant formula: Kc = [products]^coefficients / [reactants]^coefficients
Quadratic equation formula: ax^2 + bx + c = 0

Theorems

Quadratic Formula Theorem

Suitable Grade Level

College Level Chemistry