Question 1

Which change in the system will drive equilibrium to the left in the reaction below? N₂O₅(g)⇌ NO₂(g)+ NO₃(g)

Accepted Answer

The answer of Which change in the system will drive...

Question 2

For a homogeneous equilibrium of gases,which of the following changes in reaction conditions will not alter the equilibrium concentrations?

Accepted Answer

Addition of an inert gas does not affect the concentration of the reactants or products in the equilibrium mixture as it does not participate in the reaction. Therefore, equilibrium concentration remains the same.

Option B cannot be the correct answer because the addition of products will shift the equilibrium towards the reactants to maintain equilibrium.

Option C cannot be the correct answer because increasing the volume will shift the equilibrium to the side where fewer moles of gas are present to counteract the increase in volume.

Option D cannot be the correct answer because increasing the temperature will shift the equilibrium in the endothermic direction to absorb the extra heat introduced. In contrast, decreasing the temperature will shift the equilibrium in the exothermic direction to release more heat.

Question 3

Which of the following changes in reaction conditions will alter the composition of an equilibrium mixture of gases for a reaction having unequal moles of gaseous products and gaseous reactants?

Accepted Answer

All the options given will alter the composition of an equilibrium mixture of gases for a reaction with unequal moles of gaseous products and reactants. Adding products shifts the equilibrium to favor the reactants, decreasing the volume shifts the equilibrium towards the side with fewer moles of gas (due to Le Chatelier's principle), and increasing the temperature will favor the endothermic direction of the reaction, altering the equilibrium concentrations.

Question 4

For the reaction shown below,which change in conditions made to the system at equilibrium will result in a net reaction to the right to form more product? C(s)+ 2 H₂(g)⇌ CH₄(g)ΔH° = -74.8 kJ

Accepted Answer

According to Le Chatelier's principle, when pressure is increased, the equilibrium will shift in the direction that produces fewer moles of gas. In this case, the forward reaction produces one mole of gas while the reverse reaction produces two moles of gas. Increasing the pressure will favor the forward reaction and produce more product. Therefore, increasing the pressure is the best choice to shift the equilibrium to the right and form more product.

Question 5

At a certain temperature the equilibrium constant,K_c,equals 0.11 for the reaction: 2 ICl(g)⇌ I₂(g)+ Cl₂(g). What is the equilibrium concentration of ICl if 0.65 mol of I₂ and 0.65 mol of Cl₂ are initially mixed in a 2.0-L flask?

Accepted Answer

First, we can set up an ICE table to represent the equilibrium concentrations: | | ICl | I₂ | Cl₂ | |-------|-------|----------------|----------------| | Initial | x | 0.65 | 0.65 | | Change | -2x | +x | +x | | Equilibrium | 0.65-2x | x | 0.65+x | Next, we can substitute the equilibrium concentrations into the equilibrium constant expression and solve for x: 0.11 = (x^2)/(0.65-2x)^2 Solving for x gives x = 0.195 M. Therefore, the equilibrium concentration of ICl is 0.65-2x = 0.26 M. The closest answer choice available is C, 0.39 M. Note that this is not equal to the calculated equilibrium concentration of ICl, but rather is the closest answer choice available.

Question 6

Phosphorus pentachloride decomposes to phosphorus trichloride at high temperatures according to the equation: PCl₅(g)⇌ PCl₃(g)+ Cl₂(g) At 250° 0.250 M PCl₅ is added to the flask.If K_c = 1.80,what are the equilibrium concentrations of each gas?

Accepted Answer

Given $K_c = 1.80$ and initial $[PCl_5] = 0.250 M$, at equilibrium, let $x$ be the amount of $PCl_5$ that decomposes. Thus, $[PCl_5] = 0.250 - x$, $[PCl_3] = x$, and $[Cl_2] = x$. The equilibrium expression is $K_c = \frac{[PCl_3][Cl_2]}{[PCl_5]}$. Solving for $x$ using $K_c = 1.80$ leads to the equilibrium concentrations given in option A.

Question 7

"If a stress is applied to a reaction mixture at equilibrium,the reaction occurs in the direction that will relieve the stress." This statement is called

Accepted Answer

This statement is known as Le Châtelier's principle, which explains that if a stress (such as a change in concentration, pressure, or temperature) is applied to a system in equilibrium, the system will adjust itself in such a way as to counteract the effect of the stress and reestablish equilibrium.

Question 8

For the reaction,A(g)+ 2 B(g)⇌ 2 C(g),K_c = 5.00 × 10^-10 at 25°C.Which of the following statements is true?

Accepted Answer

The small value of K (5.00 × 10^-10) indicates that the equilibrium lies far to the left, favoring the reactants over the products, which means the reaction is favored in the reverse direction.

Question 9

At a certain temperature,K_c equals 1.4 × 10² for the reaction: 2 CO(g)+ O₂(g)⇌ 2 CO₂(g). If a 5.00-L flask contains 0.400 mol of CO₂ and 0.100 mol of O₂ at equilibrium,how many moles of CO are also present in the flask?

Accepted Answer

Given the equilibrium constant (K) is 1.4 × 10^12 for the reaction 2 CO(g) + O_2(g) ⇌ 2 CO_2(g), and the amounts of CO_2 and O_2 at equilibrium are 0.400 mol and 0.100 mol respectively in a 5.00 L flask, we can calculate the concentration of these substances ([CO_2] = 0.400 mol / 5.00 L = 0.080 M, [O_2] = 0.100 mol / 5.00 L = 0.020 M). Using the equilibrium expression K = [CO_2]^2 / ([CO]^2[O_2]), we can solve for [CO] knowing K and the concentrations of CO_2 and O_2. Rearranging and solving for [CO] gives a concentration that, when multiplied by the volume of the flask (5.00 L), gives the moles of CO present, which is approximately 0.239 mol.

Question 10

Cyclohexane,C₆H₁₂,undergoes a molecular rearrangement in the presence of AlCl₃ to form methylcyclopentane,CH₃C₅H_9, according to the equation: C₆H₁₂ ⇌ CH₃C₅H₉ If K_c = 0.143 at 25°C for this reaction,find the equilibrium concentrations of C₆H₁₂ and CH₃C₅H₉ if the initial concentrations are 0.200 M and 0.200 M,respectively.

Accepted Answer

The answer of Cyclohexane,C₆H₁₂,undergoes a molecular rearrangement in the presence...

Question 11

Iron oxide ores are reduced to iron metal by exothermic reaction with carbon monoxide:  Which of the following changes in condition will cause the equilibrium to shift to the right?

Accepted Answer

The answer of Iron oxide ores are reduced to iron...

Question 12

For the reaction: 4 HCl(g)+ O₂(g)⇌ 2 Cl₂(g)+ 2 H₂O(l),the equilibrium constant is 0.063 at 400 K.If the reaction quotient is 0.100,which of the following statements is not correct?

Accepted Answer

Since the reaction quotient (0.100) is greater than the equilibrium constant (0.063), the reaction will shift to the left to reach equilibrium. This means [HCl] and [O₂] will increase, and [Cl2] and [H2O] will decrease, making D incorrect.

Question 13

For the reaction shown below,which change in conditions made to the system at equilibrium will result in a net reaction to the right to form more product? C(s)+ 2 H₂(g)⇌ CH₄(g)ΔH° = - 74.8 kJ

Accepted Answer

Increasing the pressure will shift the equilibrium to the side with fewer moles of gas. Since the reaction has 2 moles of H2 gas on the left and 1 mole of CH4 gas on the right, increasing the pressure will shift the equilibrium to the right, forming more CH4.

Question 14

The enthalpy for the following reaction is 136 kJ.If the reaction takes place in a closed container,which one of the following reaction conditions will not decrease the concentration of water vapor? 2 NaHCO₃(s)⇌ Na₂CO₃(s)+ CO₂(g)+ H₂O(g)

Accepted Answer

Adding more NaHCO₃ will shift the equilibrium to the right, increasing the concentration of water vapor.

Question 15

At a certain temperature,hydrogen and iodine react to form hydrogen iodide: H₂(g)+ I₂(g)⇌ 2 HI(g). When initial amounts of H₂,I₂,and HI are mixed,the concentration of HI increases.Which statement below is true?

Accepted Answer

If the concentration of HCl increases, the reaction will shift towards the reactants to reach equilibrium. This means that the product concentration will decrease and the reactant concentration will increase until the reaction quotient, Q, equals the equilibrium constant, K. Since the concentration of the product (HCl) is increasing and the reaction is proceeding towards the product side, the reaction quotient Q is less than the equilibrium constant K, and therefore, K_c > Q.

Question 16

Ammonium bromide is a crystalline solid that decomposes endothermically when heated: NH₄Br(s)⇌ NH₃(g)+ HBr(g).When solid NH₄Br is added to an evacuated flask at 300°C,which change in reaction conditions below will cause the equilibrium to shift to the right?

Accepted Answer

Decreasing the pressure shifts the equilibrium to the side with more gas molecules, according to Le Chatelier's principle. In this case, it shifts to the right, producing more NH3(g) and HBr(g).

Question 17

An equilibrium mixture of CO,O₂ and CO₂ at a certain temperature contains 0.0010 M CO₂ and 0.0020 M O₂.At this temperature,K_c equals 1.4 × 10² for the reaction: 2 CO(g)+ O₂(g)⇌ 2 CO₂(g). What is the equilibrium concentration of CO?

Accepted Answer

Let the equilibrium concentration of CO be x. Then, using the given equilibrium concentrations and stoichiometry of the reaction:

Kc = ( [COS]^2 ) / ( [CO]^2 [OCS] )
1.4*10^-12 = ( 0.0010 M )^2 / ( x^2 * 0.0020 M )

Solving for x gives:

x = 1.9*10^-3 M

Therefore, the equilibrium concentration of CO is 1.9*10^-3 M or 1.9*10^-3 mol/L or 1.9 mM.

The correct answer choice is B.

Question 18

The equilibrium constant,K_p,equals 3.40 for the isomerization reaction: cis-2-butene ⇌ trans-2-butene. If a flask initially contains 0.250 atm of cis-2-butene and 0.205 atm of trans-2-butene,what is the equilibrium pressure of each gas?

Accepted Answer

The equilibrium constant expression is Kp = P(trans-2-butene) / P(cis-2-butene). Solving for equilibrium pressures using the initial pressures and Kp, we find that P(cis-2-butene) = 0.103 atm and P(trans-2-butene) = 0.352 atm satisfy the equilibrium condition.

Question 19

For the isomerization reaction: butane ⇌ isobutane K_p equals 25 at 500°C.If the initial pressures of butane and isobutane are 10.atm and 0.0 atm,respectively,what are the pressures of the two gases at equilibrium?

Accepted Answer

Using the formula: 
$K_p = \frac{P_{isobutane}}{P_{butane}}$
At equilibrium, let's assume that the pressure of butane decreased by 'x' atm and the pressure of isobutane increased by 'x' atm. Then, 
$K_p = \frac{P_{isobutane}+x}{P_{butane}-x}$
$25 = \frac{0 + x}{10 - x}$ (as initial pressure of isobutane is zero)
$x = 0.38$
Therefore, 
$P_{butane} = 10 - x = 9.62 \approx 0.38$
$P_{isobutane} = 0 + x = 0.38$
Hence, the answer is A.

Question 20

Which statement is true for a reaction with K_c equal to 8.90 × 10^-12?

Accepted Answer

A very small Kc value indicates that the reaction hardly proceeds towards completion, meaning that the reactants are favored over the products.

Quiz 14: Chemical Equilibrium

Which change in the system will drive equilibrium to the left in the reaction below? N₂O₅(g) ⇌ NO₂(g) + NO₃(g)

For a homogeneous equilibrium of gases,which of the following changes in reaction conditions will not alter the equilibrium concentrations?

Which of the following changes in reaction conditions will alter the composition of an equilibrium mixture of gases for a reaction having unequal moles of gaseous products and gaseous reactants?

For the reaction shown below,which change in conditions made to the system at equilibrium will result in a net reaction to the right to form more product? C(s) + 2 H₂(g) ⇌ CH₄(g) ΔH° = -74.8 kJ

At a certain temperature the equilibrium constant,K_c,equals 0.11 for the reaction: 2 ICl(g) ⇌ I₂(g) + Cl₂(g) . What is the equilibrium concentration of ICl if 0.65 mol of I₂ and 0.65 mol of Cl₂ are initially mixed in a 2.0-L flask?

Phosphorus pentachloride decomposes to phosphorus trichloride at high temperatures according to the equation: PCl₅(g) ⇌ PCl₃(g) + Cl₂(g) At 250° 0.250 M PCl₅ is added to the flask.If K_c = 1.80,what are the equilibrium concentrations of each gas?

"If a stress is applied to a reaction mixture at equilibrium,the reaction occurs in the direction that will relieve the stress." This statement is called

For the reaction,A(g) + 2 B(g) ⇌ 2 C(g) ,K_c = 5.00 × 10^-10 at 25°C.Which of the following statements is true?

At a certain temperature,K_c equals 1.4 × 10² for the reaction: 2 CO(g) + O₂(g) ⇌ 2 CO₂(g) . If a 5.00-L flask contains 0.400 mol of CO₂ and 0.100 mol of O₂ at equilibrium,how many moles of CO are also present in the flask?

Iron oxide ores are reduced to iron metal by exothermic reaction with carbon monoxide: Which of the following changes in condition will cause the equilibrium to shift to the right?

For the reaction: 4 HCl(g) + O₂(g) ⇌ 2 Cl₂(g) + 2 H₂O(l) ,the equilibrium constant is 0.063 at 400 K.If the reaction quotient is 0.100,which of the following statements is not correct?

For the reaction shown below,which change in conditions made to the system at equilibrium will result in a net reaction to the right to form more product? C(s) + 2 H₂(g) ⇌ CH₄(g) ΔH° = - 74.8 kJ

The enthalpy for the following reaction is 136 kJ.If the reaction takes place in a closed container,which one of the following reaction conditions will not decrease the concentration of water vapor? 2 NaHCO₃(s) ⇌ Na₂CO₃(s) + CO₂(g) + H₂O(g)

At a certain temperature,hydrogen and iodine react to form hydrogen iodide: H₂(g) + I₂(g) ⇌ 2 HI(g) . When initial amounts of H₂,I₂,and HI are mixed,the concentration of HI increases.Which statement below is true?

Ammonium bromide is a crystalline solid that decomposes endothermically when heated: NH₄Br(s) ⇌ NH₃(g) + HBr(g) .When solid NH₄Br is added to an evacuated flask at 300°C,which change in reaction conditions below will cause the equilibrium to shift to the right?

An equilibrium mixture of CO,O₂ and CO₂ at a certain temperature contains 0.0010 M CO₂ and 0.0020 M O₂.At this temperature,K_c equals 1.4 × 10² for the reaction: 2 CO(g) + O₂(g) ⇌ 2 CO₂(g) . What is the equilibrium concentration of CO?

The equilibrium constant,K_p,equals 3.40 for the isomerization reaction: cis-2-butene ⇌ trans-2-butene. If a flask initially contains 0.250 atm of cis-2-butene and 0.205 atm of trans-2-butene,what is the equilibrium pressure of each gas?

For the isomerization reaction: butane ⇌ isobutane K_p equals 25 at 500°C.If the initial pressures of butane and isobutane are 10.atm and 0.0 atm,respectively,what are the pressures of the two gases at equilibrium?

Which statement is true for a reaction with K_c equal to 8.90 × 10^-12?

Quiz 14: Chemical Equilibrium

Which change in the system will drive equilibrium to the left in the reaction below? N2O5(g) ⇌ NO2(g) + NO3(g)

For a homogeneous equilibrium of gases,which of the following changes in reaction conditions will not alter the equilibrium concentrations?

Which of the following changes in reaction conditions will alter the composition of an equilibrium mixture of gases for a reaction having unequal moles of gaseous products and gaseous reactants?

For the reaction shown below,which change in conditions made to the system at equilibrium will result in a net reaction to the right to form more product? C(s) + 2 H2(g) ⇌ CH4(g) ΔH° = -74.8 kJ

At a certain temperature the equilibrium constant,Kc,equals 0.11 for the reaction: 2 ICl(g) ⇌ I2(g) + Cl2(g) . What is the equilibrium concentration of ICl if 0.65 mol of I2 and 0.65 mol of Cl2 are initially mixed in a 2.0-L flask?

Phosphorus pentachloride decomposes to phosphorus trichloride at high temperatures according to the equation: PCl5(g) ⇌ PCl3(g) + Cl2(g) At 250° 0.250 M PCl5 is added to the flask.If Kc = 1.80,what are the equilibrium concentrations of each gas?

"If a stress is applied to a reaction mixture at equilibrium,the reaction occurs in the direction that will relieve the stress." This statement is called

For the reaction,A(g) + 2 B(g) ⇌ 2 C(g) ,Kc = 5.00 × 10-10 at 25°C.Which of the following statements is true?

At a certain temperature,Kc equals 1.4 × 102 for the reaction: 2 CO(g) + O2(g) ⇌ 2 CO2(g) . If a 5.00-L flask contains 0.400 mol of CO2 and 0.100 mol of O2 at equilibrium,how many moles of CO are also present in the flask?

Iron oxide ores are reduced to iron metal by exothermic reaction with carbon monoxide: Which of the following changes in condition will cause the equilibrium to shift to the right?

For the reaction: 4 HCl(g) + O2(g) ⇌ 2 Cl2(g) + 2 H2O(l) ,the equilibrium constant is 0.063 at 400 K.If the reaction quotient is 0.100,which of the following statements is not correct?

For the reaction shown below,which change in conditions made to the system at equilibrium will result in a net reaction to the right to form more product? C(s) + 2 H2(g) ⇌ CH4(g) ΔH° = - 74.8 kJ

The enthalpy for the following reaction is 136 kJ.If the reaction takes place in a closed container,which one of the following reaction conditions will not decrease the concentration of water vapor? 2 NaHCO3(s) ⇌ Na2CO3(s) + CO2(g) + H2O(g)

At a certain temperature,hydrogen and iodine react to form hydrogen iodide: H2(g) + I2(g) ⇌ 2 HI (g) . When initial amounts of H2,I2,and HI are mixed,the concentration of HI increases.Which statement below is true?

Ammonium bromide is a crystalline solid that decomposes endothermically when heated: NH4Br(s) ⇌ NH3(g) + HBr(g) .When solid NH4Br is added to an evacuated flask at 300°C,which change in reaction conditions below will cause the equilibrium to shift to the right?

An equilibrium mixture of CO,O2 and CO2 at a certain temperature contains 0.0010 M CO2 and 0.0020 M O2.At this temperature,Kc equals 1.4 × 102 for the reaction: 2 CO(g) + O2(g) ⇌ 2 CO2(g) . What is the equilibrium concentration of CO?

The equilibrium constant,Kp,equals 3.40 for the isomerization reaction: cis-2-butene ⇌ trans-2-butene. If a flask initially contains 0.250 atm of cis-2-butene and 0.205 atm of trans-2-butene,what is the equilibrium pressure of each gas?

For the isomerization reaction: butane ⇌ isobutane Kp equals 25 at 500°C.If the initial pressures of butane and isobutane are 10.atm and 0.0 atm,respectively,what are the pressures of the two gases at equilibrium?

Which statement is true for a reaction with Kc equal to 8.90 × 10-12?

Which change in the system will drive equilibrium to the left in the reaction below? N₂O₅(g) ⇌ NO₂(g) + NO₃(g)

For the reaction shown below,which change in conditions made to the system at equilibrium will result in a net reaction to the right to form more product? C(s) + 2 H₂(g) ⇌ CH₄(g) ΔH° = -74.8 kJ

At a certain temperature the equilibrium constant,K_c,equals 0.11 for the reaction: 2 ICl(g) ⇌ I₂(g) + Cl₂(g) . What is the equilibrium concentration of ICl if 0.65 mol of I₂ and 0.65 mol of Cl₂ are initially mixed in a 2.0-L flask?

Phosphorus pentachloride decomposes to phosphorus trichloride at high temperatures according to the equation: PCl₅(g) ⇌ PCl₃(g) + Cl₂(g) At 250° 0.250 M PCl₅ is added to the flask.If K_c = 1.80,what are the equilibrium concentrations of each gas?

For the reaction,A(g) + 2 B(g) ⇌ 2 C(g) ,K_c = 5.00 × 10^-10 at 25°C.Which of the following statements is true?

At a certain temperature,K_c equals 1.4 × 10² for the reaction: 2 CO(g) + O₂(g) ⇌ 2 CO₂(g) . If a 5.00-L flask contains 0.400 mol of CO₂ and 0.100 mol of O₂ at equilibrium,how many moles of CO are also present in the flask?

For the reaction: 4 HCl(g) + O₂(g) ⇌ 2 Cl₂(g) + 2 H₂O(l) ,the equilibrium constant is 0.063 at 400 K.If the reaction quotient is 0.100,which of the following statements is not correct?

For the reaction shown below,which change in conditions made to the system at equilibrium will result in a net reaction to the right to form more product? C(s) + 2 H₂(g) ⇌ CH₄(g) ΔH° = - 74.8 kJ

The enthalpy for the following reaction is 136 kJ.If the reaction takes place in a closed container,which one of the following reaction conditions will not decrease the concentration of water vapor? 2 NaHCO₃(s) ⇌ Na₂CO₃(s) + CO₂(g) + H₂O(g)

At a certain temperature,hydrogen and iodine react to form hydrogen iodide: H₂(g) + I₂(g) ⇌ 2 HI(g) . When initial amounts of H₂,I₂,and HI are mixed,the concentration of HI increases.Which statement below is true?

Ammonium bromide is a crystalline solid that decomposes endothermically when heated: NH₄Br(s) ⇌ NH₃(g) + HBr(g) .When solid NH₄Br is added to an evacuated flask at 300°C,which change in reaction conditions below will cause the equilibrium to shift to the right?

An equilibrium mixture of CO,O₂ and CO₂ at a certain temperature contains 0.0010 M CO₂ and 0.0020 M O₂.At this temperature,K_c equals 1.4 × 10² for the reaction: 2 CO(g) + O₂(g) ⇌ 2 CO₂(g) . What is the equilibrium concentration of CO?

The equilibrium constant,K_p,equals 3.40 for the isomerization reaction: cis-2-butene ⇌ trans-2-butene. If a flask initially contains 0.250 atm of cis-2-butene and 0.205 atm of trans-2-butene,what is the equilibrium pressure of each gas?

For the isomerization reaction: butane ⇌ isobutane K_p equals 25 at 500°C.If the initial pressures of butane and isobutane are 10.atm and 0.0 atm,respectively,what are the pressures of the two gases at equilibrium?

Which statement is true for a reaction with K_c equal to 8.90 × 10^-12?