Brown - Chemistry: The Central Science 15th Edition - Chapter 15

Skip to main content

My Courses

Calculators AI Tools Study Prep Blog Study Prep Home

Ch.15 - Chemical Equilibrium

Back

Brown 15th Edition

Ch.15 - Chemical Equilibrium

Problem 85
At 900 °C, 𝐾_𝑐= 0.0108 for the reaction
CaCO₃(𝑠) ⇌ CaO(𝑠) + CO₂(𝑔)
A mixture of CaCO₃, CaO, and CO₂ is placed in a 10.0-L vessel at 900°C. For the following mixtures, will the amount of CaCO3 increase, decrease, or remain the same as the system approaches equilibrium?
(a) 15.0 g CaCO3, 15.0 g CaO, and 4.25 g CO2
(b) 2.50 g CaCO3, 25.0 g CaO, and 5.66 g CO2
(c) 30.5 g CaCO₃, 25.5 g CaO, and 6.48 g CO₂
Problem 86
When 1.50 mol CO2 and 1.50 mol H2 are placed in a 3.00-L container at 395 _x001F_C, the following reaction occurs: CO2(g) + H2(g) ⇌ CO(g) + H2O(g). If Kc = 0.802, what are the concentrations of each substance in the equilibrium mixture?
Problem 87a,b
The equilibrium constant constant 𝐾_𝑐 for C(𝑠) + CO₂(𝑔) ⇌ 2 CO(𝑔) is 1.9 at 1000 K and 0.133 at 298 K. (a) If excess C is allowed to react with 25.0 g of CO2 in a 3.00-L vessel at 1000 K, how many grams of CO are produced? (b) If excess C is allowed to react with 25.0 g of CO₂ in a 3.00-L vessel at 1000 K, how many grams of C are consumed?
Problem 89a
At 700 K, the equilibrium constant for the reaction CCl₄(𝑔) ⇌ C(𝑠) + 2 Cl₂(𝑔) is 𝐾_𝑝= 0.76. A flask is charged with 2.00 atm of CCl₄, which then reaches equilibrium at 700 K. (a) What fraction of the CCl₄ is converted into C and Cl₂?
Problem 89b
At 700 K, the equilibrium constant for the reaction CCl₄(𝑔) ⇌ C(𝑠) + 2 Cl₂(𝑔) is 𝐾_𝑝= 0.76. A flask is charged with 2.00 atm of CCl₄, which then reaches equilibrium at 700 K. (b) What are the partial pressures of CCl₄ and Cl₂ at equilibrium?
Problem 91
An equilibrium mixture of H2, I2, and HI at 458 _x001F_C contains 0.112 mol H2, 0.112 mol I2, and 0.775 mol HI in a 5.00-L vessel. What are the equilibrium partial pressures when equilibrium is reestablished following the addition of 0.200 mol of HI?
Problem 92d,e
Consider the hypothetical reaction A(𝑔) + 2 B(𝑔) ⇌ 2 C(𝑔), for which 𝐾_𝑐= 0.25 at a certain temperature. A 1.00-L reaction vessel is loaded with 1.00 mol of compound C, which is allowed to reach equilibrium. Let the variable x represent the number of mol/L of compound A present at equilibrium.
(d) The equation from part (c) is a cubic equation (one that has the form ax3 + bx2 + cx + d = 0). In general, cubic equations cannot be solved in closed form. However, you can estimate the solution by plotting the cubic equation in the allowed range of x that you specified in part (b). The point at which the cubic equation crosses the x-axis is the solution.
(e) From the plot in part (d), estimate the equilibrium concentrations of A, B, and C. (Hint: You can check the accuracy of your answer by substituting these concentrations into the equilibrium expression.)
Problem 93
At a temperature of 700 K, the forward and reverse rate constants for the reaction 2 HI(g) ⇌ H₂(g) + I₂(g) are k_f = 1.8×10⁻³⁰ M⁻¹s⁻¹ and k_r = 0.063 M⁻¹s⁻¹.
(a) What is the value of the equilibrium constant K_c at 700 K?
(b) Is the forward reaction endothermic or exothermic if the rate constants for the same reaction have values of k_f= 0.097 M⁻¹s⁻¹ and k_r= 2.6 M⁻¹s⁻¹ at 800 K?
Problem 94
Consider the reaction IO4- (aq) + 2 H2O (l) ⇌ H4IO6- (aq); Kc = 3.5 * 10^-2. If you start with 25.0 mL of a 0.905 M solution of NaIO4 and then dilute it with water to 500.0 mL, what is the concentration of H4IO6- at equilibrium?
Problem 95
At 800 K, the equilibrium constant for the reaction A₂(g) ⇌ 2 A(g) is K_c = 3.1 × 10^-4. (d) If the temperature is raised to 1000 K, will the reverse rate constant k_r increase or decrease? Will the change in k_r be larger or smaller than the change in k_f?
Problem 97
The protein hemoglobin (Hb) transports O2 in mammalian blood. Each Hb can bind 4 O2 molecules. The equilibrium constant for the O2 binding reaction is higher in fetal hemoglobin than in adult hemoglobin. In discussing protein oxygen-binding capacity, biochemists use a measure called the P50 value, defined as the partial pressure of oxygen at which 50% of the protein is saturated. Fetal hemoglobin has a P50 value of 19 torr, and adult hemoglobin has a P50 value of 26.8 torr. Use these data to estimate how much larger Kc is for the aqueous reaction 4 O2(aq) + Hb(aq) ⇌ Hb(O2)4(aq) in a fetus, compared to Kc for the same reaction in an adult.