Textbook Question
Which of the following reactions yield appreciable equilib- rium concentrations of both reactants and products?
(a) 2 Cu1s2 + O21g2 ∆ 2 CuO1s2; Kc = 4 * 1045
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Ch.15 - Chemical Equilibrium
Chapter 15, Problem 83
At 500 K, the equilibrium constant for the dissociation reaction H2(g) ⇌ 2H(g) is very small (Kc = 1.2 × 10⁻⁴²). (a) What is the molar concentration of H atoms at equilibrium if the equilibrium concentration of H2 is 0.10 M? (b) How many H atoms and H2 molecules are present in 1.0 L of 0.10 M H2 at 500 K?
Verified step by step guidance1
Step 1: Write the expression for the equilibrium constant (Kc) for the reaction H2(g) ⇌ 2H(g). The expression is Kc = [H]^2 / [H2].
Step 2: Substitute the given values into the Kc expression. You know Kc = 1.2 × 10⁻⁴² and [H2] = 0.10 M. So, 1.2 × 10⁻⁴² = [H]^2 / 0.10.
Step 3: Solve for [H] by rearranging the equation to find [H]^2 = Kc × [H2]. Then, calculate [H] by taking the square root of the result.
Step 4: For part (b), calculate the number of moles of H2 in 1.0 L of 0.10 M solution using the formula: moles = concentration × volume.
Step 5: Use the concentration of H atoms found in part (a) to calculate the number of moles of H atoms in 1.0 L, and then convert these moles to the number of atoms using Avogadro's number.
Related Practice
Textbook Question
The value of Kc for the reaction 3 O21g2 ∆ 2 O31g2 is 1.7 * 10-56 at 25°C. Do you expect pure air at 25 °C to contain much O3 (ozone) when O2 and O3 are in equilib- rium? If the equilibrium concentration of O2 in air at 25 °C is 8 * 10-3 M, what is the equilibrium concentration of O3?
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Open Question
Phosphine (PH3) decomposes at elevated temperatures, yielding gaseous P2 and H2: 2 PH3(g) ⇌ P2(g) + 3 H2(g), Kp = 398 at 873 K. (b) When a mixture of PH3, P2, and H2 comes to equilibrium at 873 K, P_P2 = 0.412 atm and P_H2 = 0.822 atm. What is P_PH3?
Open Question
Calculate the equilibrium concentrations of N2O4 and NO2 at 25 °C in a vessel that contains an initial N2O4 concentration of 0.0500 M. The equilibrium constant Kc for the reaction N2O4(g) ⇌ 2 NO2(g) is 4.64 × 10⁻³ at 25 °C.
Textbook Question
Calculate the equilibrium concentrations at 25 °C for the reaction in Problem 15.84 if the initial concentrations are
3N2O44 = 0.0200 M and 3NO24 = 0.0300 M.
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Open Question
A sample of HI 19.30 * 10^-3 mol^2 was placed in an empty 2.00-L container at 1000 K. After equilibrium was reached, the concentration of I2 was 6.29 * 10^-4 M. Calculate the value of Kc at 1000 K for the reaction H2(g) + I2(g) ⇌ 2 HI(g).