Which one, if any, of the following statements correctly describes a reaction at

Question

Which one, if any, of the following statements correctly describes a reaction at equilibrium? At equilibrium there is no further net reaction, with the rate at which reactants are converted to products identical to the rate at which products are converted to reactants. At equilibrium the reaction stops, such that the rate at which the reaction occurs is zero. At equilibrium the net rate of reaction depends on the concentrations of each reactant and products. At equilibrium the net rate of reaction depends on the amounts of each reactant and product. Which one of the following factors affects the value of the equilibrium constant for a reversible reaction? Adding a catalyst Removing reactant Removing product Raising the temperature Consider the reaction N_2(g) + O_2(g) Rightarrow 2 NO(g) occurring with K_p = 1.0 times 10^-2 at 2000 Degree C. What happens when 0.40 bar of N_2 0.10 bar of O_2, and 0.080 bar of NO are placed in a previously evacuated rigid container held at this temperature? The partial pressures of NO decreases; the partial pressures of N_2 and O_2 increase. The partial pressures of NO decreases; the partial pressures of N_2 and O_2 remain unchanged. The partial pressures of NO increases; the partial pressures of N_2 and O_2 decrease. The partial pressures of NO remains unchanged; the partial pressures of N_2 and O_2 increase. The system is at equilibrium, and the partial pressures do not change. The reaction 2 NO_2(g) Rightarrow 2 NO(g) reaches equilibrium at an unspecified temperature when the concentrations of nitrogen dioxide and oxygen arc 3.0 M each and the concentration of nitrogen monoxide is 6.0 M. What is the value for the equilibrium constant in terms of concentrations at this temperature? The molar solubility of AgCl(s) in pure water at 25 Degree C is [AgCl]_ = s = 1.34 times 10^-5 M. Determine the solubility product K_sp for AgCl(s) Rightarrow Ag^+(aq) + Cl^-(aq). Assume ideal behavior. The entropy increases during which of the following processes: Freezing liquid water Dissolving sodium chloride crystals into liquid water Expanding argon gas isothermally from 2 bar to 1 bar Chilling a steel ball bearing from 100 degree C to 25 degree C Crystallizing a protein from an aqueous solution. An iron piston in a compressor has a mass of 3.62 Kg. If the specific heat of iron is 0.449 J/g degree C, how much heat is required to raise the temperature of the piston from 12.0 degree C to 111.0 degree C? The reaction, SiCl_4(g) + 2 H_2(g) rightarrow Si(s) + 4 HCl(g), for which standard enthalpy of change of reaction (delta h) = + 293.5 KJ/mole, take place in a reactor. The amount of silicon deposited at equilibrium when the volume of the reactor is increased: Increases Decreases Remains Unchanged Determine the change in Gibbs free energy (in Kj/mol) for the mixing of ice and liquid water at the normal melting point of water. Consider the following reaction: 2 Fe(s) + 3 CO_2(g) rightarrow Fe_2O_3(s) + 3 CO(g) What must be the temperature (in K) if ? Which one, if any, of the following statements correctly describes what happens in a hydrogen in a hydrogen fuel cell, where the unbalanced reaction H_2(g) + O_2(g) Rightaroow H_2O(l) occurs? Both H and O are reduced. H is reduced while O is oxidized. H is oxidized while O is reduced. Both H and O are oxidized. None of the above statements are correct. Which one of the following sets of 1/2 reactions is possible at the cathode of an electrochemical cell?

Explanation / Answer

36) Answer A;

37) Answer : D
If the temperature of a system is changed, a change in the value of Kc occurs. An increase in temperature always shifts
the equilibrium in the direction of the endothermic reaction, while a temperature decrease shifts the equilibrium in the
direction of the exothermic reaction. Therefore, for endothermic reactions the value of Kc increases with increasing
temperature, and for exothermic reactions the value of Kc decreases with increasing temperature.

38) K = [NO]2/([N2]x[O2]
Kp = pNO2/pN2xpO2 = ([NO]xRT)2/(([N2]xRT)x([O2]xRT)) = [NO]2/([N2]x[O2] = K
To calculate the equilibrium position, one has to go through the following steps:

                           N2(g)    +   O2(g) ---> 2 NO(g)
Initial pressures:        0.40           0.10          0.08
Equilibrium pressures: 0.40 + x          0.1 + x      0.08 - 2x

Kp = 1.0 x 10-2 = (0.08 -2x)2/(0.40 + x)(0.1 + x)
0.01 (x2 + 0.5x + 0.04) = 4x2 - 0.32x + 0.0064
3.99x2 - 0.325 x + 0.006 = 0

x = 0.053

Therefore;
pN2 (eq) = 0.4 + 0.053 = 0.453 bar
pO2 (eq) = 0.1 + 0.053 = 0.153 bar
pNO (eq) = 0.08 + 0.053 = 0.027 bar

So, the partial pressure of NO decreases and the partial pressure of N2 and O2 increases.
Therefore, answer : A

39) 2 NO2 (g) ----> 2 NO(g) + O2 (g)
Kc = [NO]2[O2]/[NO2]2 = (3.0)^2 x (3.0)/ (6.0)^2 = 0.75

Kc = 0.75

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