1))At equilibrium, ________. CH 4 (g) + 2 H 2 O (g) CO 2 (g) + 4 H 2 (g) 3)) the
ID: 1082761 • Letter: 1
Question
1))At equilibrium, ________.
CH4 (g) + 2 H2O(g) CO2(g) + 4 H2 (g)
3))
the rates of the forward and reverse reactions are equal
the value of the equilibrium constant is 1
all chemical reactions have ceased
the rate constants of the forward and reverse reactions are equal
the limiting reagent has been consumed
2))Which of the following expressions is the correct equilibrium-constant expression for the equilibrium given below:
The equilibrium-constant expression depends on the ________ of the reaction.
1.56 x 104
9.50 x 1018
6.44 x 105
5.26 x 10-20
1.90 x 1019
5))
stoichiometry
mechanism
the quantities of reactants and products initially present
temperature
stoichiometry and mechanism
4))
Given the following reaction at equilibrium, if Kc = 1.90 × 1019 at 25.0 °C, Kp = ________.
H2 (g) + Br2 (g) 2 HBr (g)
The Keq for the equilibrium below is 7.52 × 10-2 at 480.0 °C.
2Cl2 (g) + 2H2O (g) 4HCl (g) + O2 (g)
What is the value of Keq at this temperature for the following reaction?
2HCl (g) + 1/2 O2 (g) Cl2 (g) + H2O (g)
Br2 (g) + Cl2 (g) 2BrCl (g)
is Kp = 7.0. A closed vessel at 400 K is charged with 1.00 atm of Br2 (g), 1.00 atm of Cl2 (g), and 2.00 atm of BrCl (g). Use Q to determine which of the statements below is true.
The equilibrium partial pressures of Br2, Cl2, and BrCl will be the same as the initial values.
The reaction will go to completion since there are equal amounts of Br2 and Cl2.
At equilibrium, the total pressure in the vessel will be less than the initial total pressure.
The equilibrium partial pressure of Br2 will be greater than 1.00 atm.
The equilibrium partial pressure of BrCl (g) will be 4.00 atm.
8))Which reaction will shift to the left in response to a decrease in volume?
decrease the partial pressure of O2 (g)
decrease the value of the equilibrium constant
increase the partial pressure of CO2 (g)
decrease the partial pressure of CO
increase the value of the equilibrium constant
11))The effect of a catalyst on an equilibrium is to ________.
CO (g) + 2H2(g) CH3OH(g)
At equilibrium in a particular experiment, the concentrations of CO and H2 were 0.15 M and 0.36 M respectively. What is the equilibrium concentration of CH3OH? The value of Keq for this reaction is 14.5 at the temperature of the experiment.
increase the equilibrium constant so that products are favored
slow the reverse reaction only
shift the equilibrium to the right
increase the rate of the forward reaction only
increase the rate at which equilibrium is achieved without changing the composition of the equilibrium mixture
12)Consider the following chemical reaction:
a decrease in the total pressure (T constant)
a decrease in the total volume of the reaction vessel (T constant)
addition of some N2 to the reaction vessel (V and T constant)
some removal of NH3 from the reaction vessel (V and T constant)
an increase in total pressure by the addition of helium gas (V and T constant)
10))
Consider the following reaction at equilibrium:
2CO2 (g) 2CO (g) + O2 (g) H° = -514 kJ
Le Châtelier's principle predicts that a decrease in temperature will ________.
4 Fe (s) + 3 O2 (g) 2 Fe2O3 (s)
N2 (g) + 3H2 (g) 2 NH3 (g)
H2 (g) + Cl2 (g) 2 HCl (g)
2 SO3 (g) 2 SO2 (g) + O2 (g)
2HI (g) H2 (g) + I2 (g)
9))
Consider the following reaction at equilibrium:
2NH3 (g) N2 (g) + 3H2 (g)
Le Châtelier's principle predicts that the moles of H2 in the reaction container will increase with ________.
products predominate
roughly equal amounts of products and reactants are present
only reactants are present
only products are present
reactants predominate
7))At 400 K, the equilibrium constant for the reaction
3.65
5.66 x 10-3
13.3
-0.0376
0.274
6))
The equilibrium constant for the gas phase reaction
H2 (g) + I2 (g) 2HI (g)
is Keq = 50 at 300 °C. At equilibrium, ________.
13))A reaction vessel is charged with hydrogen iodide, which partially decomposes to molecular hydrogen and iodine:
2HI (g) H2(g) + I2(g)
When the system comes to equilibrium at 425 °C the partial pressure of HI is 0.708 atm, and the partial pressures of H2 and I2 are both 0.0960 atm. The value of Kp at this temperature is ________.
Carbon monoxide and chlorine gas react to produce COCl2 gas. The Kp for the reaction is 1.49 × 108at 100.0 °C: In an equilibrium mixture of the three gases, PCO = PCl2 = 7.70 × 10-4 atm. The partial pressure of the product, phosgene ( COCl2 ), is ________ atm.
CaCO3 (s) CaO (s) + CO2 (g)
Le Châtelier's principle predicts that ________ will result in an increase in the number of moles of CO2.
CH4 (g) + 2 H2O (g) CO2 (g) + 4 H2 (g) H = +190 kJ
When CH4 is added :
2NO(g) + Cl2(g) 2NOCl(g)
What is Qc for this reaction? In which direction must the system proceed to reach equilibrium?
1.7 x 10-4, To the left
7.8 x 107 , To the left
1.7 x 10-4, To the right
4.3 x 104 , To the left
4.3 x 104 , To the right
7.8 x 107 , To the right
final)))
At elevated temperatures, molecular hydrogen and molecular bromine react to partially form hydrogen bromide:
H2 (g) + Br2 (g) 2HBr (g)
A mixture of 0.682 mol of H2 and 0.440 mol of Br2 is combined in a reaction vessel with a volume of 2.00 L. At equilibrium at 700 K, there are 0.546 mol of H2 present. At equilibrium, there are ________ mol of Br2 present in the reaction vessel.
the reactions shifts to the right
H increases
there is no change
Keq decreases
the reaction shifts to the left
20))The equilibrium constant Kc for the formation of nitrosyl chlorine from nitric acid and molecular chlorine is 6.5 x 104 at 35°C. In a certain experiment, 2.0 x 10-2 moles of NO, 8.3 x 10-3 moles of Cl2 and 7.2 moles of NOCl are mixed in a 5.0 L flask and are allowed to reach equilibrium.
increasing the temperature
decreasing the temperature
increasing the pressure
removing some of the CaCO3
None of the above
19))For the reaction:
2.51 × 1014
1.92 × 1011
1.15 × 105
3.98 × 10-15
8.83 × 101
17))Kp = 0.0198 at 721 K for the reaction
2HI (g) H2(g) + I2(g)
In a particular experiment, the partial pressures of H2 and I2 at equilibrium are 0.678 and 0.788 atm, respectively. The partial pressure of HI is ________ atm.
18))For the endothermic reaction
54.3
1.84 x 10-2
1.3 x 10-2
Kp cannot be calculated for this gas reaction when the volume of the reaction vessel is not given.
6.8 x 10-2
14))A sealed 1.0 L flask is charged with 0.500 mol of I2 and 0.500 mol of Br2. An equilibrium reaction ensues:
I2 (g) + Br2 (g) 2IBr (g)
When the container contents achieve equilibrium, the flask contains 0.84 mol of IBr. The value of Keq is ________.
15)))))))The equilibrium constant (Kp) for the interconversion of PCl5 and PCl3 is 0.0121. A vessel is charged with PCl5 giving an initial pressure of 0.123 atm and yields PCl3 and Cl2. At equilibrium, the partial pressure of PCl3 is ________ atm.
0.123
0.0330
0.0455
0.0782
0.0908
16))))
3))
Explanation / Answer
For the given combustion of methane in oxygen-rich environment, at equilibrium, the rates of forward and reverse reactions will be equal. This is why chemical equilibria are considered as dynamic equilibria instead of static ones as the forward and reverse reactions continue to occur even after the system as attained equilibrium. Only because the rates of forward and backward reactions are equal is the system apparently at a standstill to the observer. Moreover the given reaction type usually attains equilibrium only when the limiting reagent is completely consumed as the complete consumption drives the reverse reaction which can be explained by Le Chatlier's principle but at equilibrium there is always a certain quantity of the limiting reagent present from the decomposition of the products. In terms of the rate laws of the forward and backward reactions of the given equilibrium, it can be observed that the rate constants themselves are equal and so are the rates at equilibrium. Finally since the rates of forward and reverse reactions are equal at equilibrium, the equilbrium constant will be one. Therefore, the correct statements among the given about equilibrium are:
the rates of the forward and reverse reactions are equal
the value of the equilibrium constant is 1
the rate constants of the forward and reverse reactions are equal
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