Question 1

Gaseous hydrogen bromide decomposes at elevated temperatures according to the following equation: 2 HBr(g)⇌ H₂(g)+ Br₂(g). At a certain temperature a 2.00 L flask is initially filled only with 0.600 mol of HBr.What is the value of K_c at that temperature if the flask contains 0.104 mol of H₂ at equilibrium?

Accepted Answer

The equilibrium constant expression for this reaction is:K_c = [H₂][Br₂]/[HBr]²At equilibrium, the concentrations of the gases are:[H₂] = 0.104 mol/2.00 L = 0.0520 M[Br₂] = 0.104 mol/2.00 L = 0.0520 M[HBr] = (0.600 mol - 2(0.104 mol))/2.00 L = 0.196 MSubstituting these values into the equilibrium constant expression, we get:K_c = (0.0520 M)(0.0520 M)/(0.196 M)² = 7.04 × 10^-2

Question 2

The solubility of 1:1 salts is measured by the equilibrium constant for the general reaction: MX(s)= Mⁿ⁺(aq)+ X^n-(aq).Given the following salts and their equilibrium constants for the reaction above at 25°C,which salt is the least soluble?

Accepted Answer

The solubility of a salt is inversely related to the value of its equilibrium constant. The salt with the smallest equilibrium constant is the least soluble. SrCO3 has the smallest equilibrium constant (5.6 × 10^-10), making it the least soluble.

Question 3

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 concentration of H₂ will shift the equilibrium to the right, according to Le Chatelier's principle, to form more CH₄.

Question 4

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

The answer of The enthalpy for the following reaction is...

Question 5

A crude type of disappearing ink is based on the following endothermic equilibrium: [Co(H₂O)₆]Cl₂ (aq)⇌ [CoCl₂(H₂O)₄] (aq)+ 2 H₂O (l) (colorless)(blue) If the reactant solution is used to write on a piece of paper and the paper is allowed to partially dry,what can be done to bring out the colored handwriting?

Accepted Answer

The answer of A crude type of disappearing ink is...

Question 6

For acid solutions of the same molarity acid strength is proportional to the equilibrium concentration of H₃O⁺.For equimolar solutions of acids,which equilibrium expression below corresponds to the strongest acid?

Accepted Answer

The answer of For acid solutions of the same molarity...

Question 7

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

Doubling the volume of the container decreases the pressure, which shifts the equilibrium to the right to produce more gas molecules, according to Le Chatelier's principle.

Question 8

Ammonium carbamate can dissociate into gases at 25°C according to the reaction: NH₂COONH₄(s)⇌ 2 NH₃(g)+ CO₂(g) If sufficient ammonium carbamate is sealed in a flask,the total pressure will be 0.117 atm at equilibrium.What is the value of K_p at 25°C?

Accepted Answer

The equilibrium expression for the dissociation of ammonium carbamate into gases is given by $K_p = \frac{P_{NH_3}^2 \cdot P_{CO_2}}{P_{solid}}$. Since the pressure of the solid is constant and not included in the $K_p$ expression, we can simplify the expression to $K_p = P_{NH_3}^2 \cdot P_{CO_2}$. At equilibrium, the total pressure ($P_{total}$) is the sum of the partial pressures of $NH_3$ and $CO_2$. Given that $2NH_3$ and $1CO_2$ are produced, for every mole of ammonium carbamate that dissociates, the ratio of $NH_3$ to $CO_2$ will be 2:1. Therefore, if $x$ is the partial pressure of $CO_2$, then $2x$ will be the partial pressure of $NH_3$, making $P_{total} = 3x = 0.117$ atm. Solving for $x$ gives $x = 0.039$ atm. Substituting these values into the $K_p$ expression gives $K_p = (2x)^2 \cdot x = (2 \cdot 0.039)^2 \cdot 0.039 = 2.37 \times 10^{-4}$.

Question 9

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

Accepted Answer

Adding an inert gas does not change the concentrations of reactants or products in the reaction mixture, and therefore does not affect the equilibrium concentrations. Inert gases do not participate in the chemical reaction and thus do not disturb the equilibrium. On the other hand, adding reactants or products will shift the equilibrium to one direction, decreasing the concentration of the added substance and increasing the concentration of the other substances to re-establish the equilibrium. Similarly, decreasing the pressure or volume will also shift the equilibrium to the side with fewer moles of gas, while increasing the temperature will shift the equilibrium in the direction that absorbs heat (endothermic) or releases heat (exothermic).

Question 10

Oxalic acid can donate two protons to water in successive reactions: (1)H₂C₂O₄(aq)+ H₂O(l)⇌ H₃O⁺(aq)+ HC₂O₄^-(aq) (2)HC₂O₄^-(aq)+ H₂O(l)⇌ H₃O⁺(aq)+ C₂O₄^2-(aq) If K_c1 = 5.9 × 10^-2 and K_c2 = 6.4 × 10^-5 at 25°C,what is the value of K_c for reaction (3)? (3)H₂C₂O₄(aq)+ 2 H₂O(l)⇌ 2 H₃O⁺(aq)+ C₂O₄^2-(aq)

Accepted Answer

The overall equilibrium constant $K_c$ for reaction (3) is the product of the equilibrium constants for reactions (1) and (2), i.e., $K_{c1} \times K_{c2} = 5.9 \times 10^{-2} \times 6.4 \times 10^{-5} = 3.776 \times 10^{-6}$, which is approximately $3.8 \times 10^{-6}$.

Question 11

The pink and blue species below form a violet colored mixture at equilibrium: [Co(H₂O)₆]²⁺ (aq)+ 4 Cl^- (aq)⇌ [CoCl₄]^2- (aq)+ 6 H₂O (l) (pink)(blue) If the concentration of [Co(H₂O)₆]²⁺ is increased,what happens to the solution?

Accepted Answer

According to Le Chatelier's Principle, if the concentration of one of the species in equilibrium is increased, the equilibrium will shift in the direction that consumes that species. In this case, we can see that the species being consumed is [Co(H₂O)₆]²⁺, which is pink in color. Therefore, as more of this species is consumed, the solution will shift towards the blue-colored species and increase the concentration of [CoCl₄]^2-.

Question 12

Iron oxide ores are reduced to iron metal by exothermic reaction with carbon monoxide: FeO(s)+ CO(g)⇌ Fe(s)+ CO₂(g) Which of the following changes in condition will cause the equilibrium to shift to the right?

Accepted Answer

According to Le Chatelier's principle, an increase in the concentration of CO will shift the equilibrium to the right in order to consume the excess CO. Therefore, adding CO will cause the equilibrium to shift to the right. Adding FeO or CO₂ will increase the concentrations of the reactants and will shift the equilibrium to the left to consume the excess, while raising the temperature will favor the endothermic direction, shifting the equilibrium to the left. Therefore, only adding CO is the best choice to shift the equilibrium to the right.

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

According to Le Chatelier's principle, when the volume is decreased, the equilibrium will shift in the direction that produces fewer moles of gas. In this case, CH4 has only one mole of gas, while C and H2S each have zero moles of gas, so decreasing the volume will shift the equilibrium to the right, favoring the formation of more CH4. Thus, choice C will result in a net reaction to the right to form more product. Adding He or more C will not affect the equilibrium because they are not part of the reaction. Increasing the volume will favor the formation of more gases, but there are no additional moles of gas on either side of the reaction, so it will not affect the equilibrium.

Question 14

Salt solubilities can be compared by the concentration of cation formed when the salt dissolves in the general reaction: M_aX_b(s)⇌ a M^b+(aq)+ b X^a-(aq).Given the following salts and their equilibrium constants for the reaction above at 25°C,which salt is the least soluble?

Accepted Answer

The least soluble salt is the one with the lowest solubility product constant (Ksp). AgCl has the lowest Ksp value (1.8 × 10^-10), indicating it is the least soluble among the given options.

Question 15

"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

Le Châtelier's principle states that if a stress, such as a change in temperature, pressure, or concentration, is applied to a reaction mixture at equilibrium, the reaction will shift in the direction that partially counteracts the effect of the stress. This principle helps to predict the effect of changes on the equilibrium position of a reaction.

Question 16

Acids donate protons to water according to the general equation: HA(aq)+ H₂O(l)⇌ H₃O⁺(aq)+ A^-(aq) Consider the following acids and their equilibrium constants for reaction with water at 25°C.If all the acids have the same initial concentration,which is the strongest acid (i.e.which donates the most protons to water)?

Accepted Answer

HIOS3 has the highest equilibrium constant (Ka = 1.7 × 10^-1), indicating it donates the most protons to water, making it the strongest acid among the options.

Question 17

The equilibrium constant K_cfor the reaction HF(aq)+ H₂O(l)⇌ H₃O⁺(aq)+F^-(aq)is 3.5 × 10^-4.What is the equilibrium concentration of H₃O⁺ if the initial concentration of HF is 1.0 M?

Accepted Answer

The balanced chemical equation for the reaction is:
HF(aq) + HSO4⁻(aq) ↔ HSO3⁻(aq) + F⁻(aq) + H2O(l)
The equilibrium constant (K) is given as:
K = [HSO3⁻][F⁻]/[HF][HSO4⁻]
K = 3.5 × 10⁻⁴
The initial concentration of HF is 1.0 M. Let the equilibrium concentration of HSO3⁻ be x.
At equilibrium, the concentration of F⁻ and HSO4⁻ will also be x (due to stoichiometry).
Therefore, the concentration of HF and HSO4⁻ will be (1.0 - x) M.
Substituting the values into the equilibrium constant expression:
3.5 × 10⁻⁴ = x²/(1.0 - x)
Solving for x using the quadratic formula gives:
x = 1.9 × 10⁻² M
Therefore, the equilibrium concentration of HSO3⁻ is 1.9 × 10⁻² M, which is equivalent to the concentration of HSO3⁻ and F⁻.

Question 18

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 of these changes can shift the equilibrium position: adding reactants or products changes concentrations, altering pressure or volume affects reactions with unequal moles of gases, and changing temperature affects the equilibrium constant.

Question 19

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

Lowering the temperature will shift the equilibrium to the right for an exothermic reaction, as it favors the formation of products.

Question 20

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

Accepted Answer

Increasing the pressure will shift the equilibrium towards the side with fewer moles of gas, which is the left side in this reaction.

Quiz 13: Chemical Equilibrium

The solubility of 1:1 salts is measured by the equilibrium constant for the general reaction: MX(s) = Mⁿ⁺(aq) + X^n-(aq) .Given the following salts and their equilibrium constants for the reaction above at 25°C,which salt is the least soluble?

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)

For acid solutions of the same molarity acid strength is proportional to the equilibrium concentration of H₃O⁺.For equimolar solutions of acids,which equilibrium expression below corresponds to the strongest acid?

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?

Ammonium carbamate can dissociate into gases at 25°C according to the reaction: NH₂COONH₄(s) ⇌ 2 NH₃(g) + CO₂(g) If sufficient ammonium carbamate is sealed in a flask,the total pressure will be 0.117 atm at equilibrium.What is the value of K_p at 25°C?

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

The pink and blue species below form a violet colored mixture at equilibrium: [Co(H₂O) ₆]²⁺ (aq) + 4 Cl^- (aq) ⇌ [CoCl₄]^2- (aq) + 6 H₂O (l) (pink) (blue) If the concentration of [Co(H₂O) ₆]²⁺ is increased,what happens to the solution?

Iron oxide ores are reduced to iron metal by exothermic reaction with carbon monoxide: FeO(s) + CO(g) ⇌ Fe(s) + CO₂(g) Which of the following changes in condition will cause the equilibrium to shift to the right?

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

Salt solubilities can be compared by the concentration of cation formed when the salt dissolves in the general reaction: M_aX_b(s) ⇌ a M^b+(aq) + b X^a-(aq) .Given the following salts and their equilibrium constants for the reaction above at 25°C,which salt is the least soluble?

"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

The equilibrium constant K_cfor the reaction HF(aq) + H₂O(l) ⇌ H₃O⁺(aq) +F^-(aq) is 3.5 × 10^-4.What is the equilibrium concentration of H₃O⁺ if the initial concentration of HF is 1.0 M?

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

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

Quiz 13: Chemical Equilibrium

The solubility of 1:1 salts is measured by the equilibrium constant for the general reaction: MX(s) = Mn+(aq) + Xn-(aq) .Given the following salts and their equilibrium constants for the reaction above at 25°C,which salt is the least soluble?

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)

For acid solutions of the same molarity acid strength is proportional to the equilibrium concentration of H3O+.For equimolar solutions of acids,which equilibrium expression below corresponds to the strongest acid?

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?

Ammonium carbamate can dissociate into gases at 25°C according to the reaction: NH2COONH4(s) ⇌ 2 NH3(g) + CO2(g) If sufficient ammonium carbamate is sealed in a flask,the total pressure will be 0.117 atm at equilibrium.What is the value of Kp at 25°C?

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

The pink and blue species below form a violet colored mixture at equilibrium: [Co(H2O) 6]2+ (aq) + 4 Cl- (aq) ⇌ [CoCl4]2- (aq) + 6 H2O (l) (pink) (blue) If the concentration of [Co(H2O) 6]2+ is increased,what happens to the solution?

Iron oxide ores are reduced to iron metal by exothermic reaction with carbon monoxide: FeO(s) + CO(g) ⇌ Fe(s) + CO2(g) Which of the following changes in condition will cause the equilibrium to shift to the right?

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

Salt solubilities can be compared by the concentration of cation formed when the salt dissolves in the general reaction: MaXb(s) ⇌ a Mb+(aq) + b Xa-(aq) .Given the following salts and their equilibrium constants for the reaction above at 25°C,which salt is the least soluble?

"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

The equilibrium constant Kc for the reaction HF(aq) + H2O(l) ⇌ H3O+(aq) +F-(aq) is 3.5 × 10-4.What is the equilibrium concentration of H3O+ if the initial concentration of HF is 1.0 M?

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

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

The solubility of 1:1 salts is measured by the equilibrium constant for the general reaction: MX(s) = Mⁿ⁺(aq) + X^n-(aq) .Given the following salts and their equilibrium constants for the reaction above at 25°C,which salt is the least soluble?

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)

For acid solutions of the same molarity acid strength is proportional to the equilibrium concentration of H₃O⁺.For equimolar solutions of acids,which equilibrium expression below corresponds to the strongest acid?

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?

Ammonium carbamate can dissociate into gases at 25°C according to the reaction: NH₂COONH₄(s) ⇌ 2 NH₃(g) + CO₂(g) If sufficient ammonium carbamate is sealed in a flask,the total pressure will be 0.117 atm at equilibrium.What is the value of K_p at 25°C?

The pink and blue species below form a violet colored mixture at equilibrium: [Co(H₂O) ₆]²⁺ (aq) + 4 Cl^- (aq) ⇌ [CoCl₄]^2- (aq) + 6 H₂O (l) (pink) (blue) If the concentration of [Co(H₂O) ₆]²⁺ is increased,what happens to the solution?

Iron oxide ores are reduced to iron metal by exothermic reaction with carbon monoxide: FeO(s) + CO(g) ⇌ Fe(s) + CO₂(g) Which of the following changes in condition will cause the equilibrium to shift to the right?

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

Salt solubilities can be compared by the concentration of cation formed when the salt dissolves in the general reaction: M_aX_b(s) ⇌ a M^b+(aq) + b X^a-(aq) .Given the following salts and their equilibrium constants for the reaction above at 25°C,which salt is the least soluble?

The equilibrium constant K_cfor the reaction HF(aq) + H₂O(l) ⇌ H₃O⁺(aq) +F^-(aq) is 3.5 × 10^-4.What is the equilibrium concentration of H₃O⁺ if the initial concentration of HF is 1.0 M?

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

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