Chemical Equilibrium Fundamentals

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Questions and Answers

What is the purpose of writing an equilibrium constant expression?

To determine the initial concentrations of reactants only

To find the amount of products at the start of the reaction

To find out how fast the reaction occurs

To establish the relationship between reactants and products at equilibrium (correct)

When given the initial and equilibrium concentrations of reactants, what is typically necessary to find the equilibrium concentrations of products?

The final concentrations of all substances

The temperature of the reaction

The use of a stoichiometric table (correct)

An understanding of reaction rates

Which of the following statements regarding heterogeneous equilibria is correct?

Heterogeneous equilibria do not exist in chemical reactions

Only the concentration of gaseous and aqueous species are included in the equilibrium expression (correct)

All phases of reactants and products must be in the same state

Solid and liquid concentrations are included in the equilibrium constant expression

How does Le Chatelier's Principle predict the effect of increasing the concentration of reactants on a reaction at equilibrium?

It shifts the equilibrium to favor product formation Signup and view all the answers

Why is it important to express the final answer for an equilibrium constant to the correct number of significant figures?

To reflect the precision of the measurements used in calculations Signup and view all the answers

What is the correct expression for the equilibrium constant $K_p$ of the reaction $A(g) + bB(g) \rightleftharpoons cC(g) + dD(g)$?

$K_p = \frac{P_C^c P_D^d}{P_A^a P_B^b}$ Signup and view all the answers

In an equilibrium expression, which substances are excluded?

Solids and Liquids Signup and view all the answers

What happens to the equilibrium constant $K$ when the temperature of a reaction changes?

It changes depending on the reaction Signup and view all the answers

Which of the following reactions represents a homogeneous equilibrium?

$A(g) + B(g) \rightleftharpoons C(g)$ Signup and view all the answers

Which statement best describes Le Chatelier's Principle?

An increase in concentration of reactants will shift the equilibrium to the right. Signup and view all the answers

How is the reaction quotient $Q$ related to the equilibrium constant $K$?

Both B and C are correct. Signup and view all the answers

In the equilibrium expression, what does the coefficient in front of a product or reactant represent?

Stoichiometric relationship Signup and view all the answers

What is an important characteristic of heterogeneous equilibria?

Solids and liquids do not appear in the equilibrium expression. Signup and view all the answers

What is the correct formula to calculate the concentration of a substance?

Concentration = Number of moles / Volume Signup and view all the answers

In a homogeneous equilibrium, how are the reactants and products distributed?

They are in the same phase. Signup and view all the answers

What does the equilibrium constant (K) indicate about a reaction?

The ratio of the concentrations of products to reactants at equilibrium. Signup and view all the answers

Given a reaction mixture of 0.235 moles of ethanoic acid in 1000 cm³, what is the concentration of ethanoic acid?

0.235 mol/dm³ Signup and view all the answers

What does a reaction quotient (Q) indicate when it is compared to the equilibrium constant (K)?

Q = K indicates the reaction is at equilibrium. Signup and view all the answers

In which scenario would equilibrium shift to the left according to Le Chatelier's Principle?

Adding more products. Signup and view all the answers

Which of the following is true about heterogeneous equilibria?

They can involve a mix of phases including solids, liquids, and gases. Signup and view all the answers

When given 0.182 moles of water in a reaction mixture of 1000 cm³, what is the concentration of water?

0.182 mol/dm³ Signup and view all the answers

What does a very large value of the equilibrium constant indicate about the equilibrium position?

It suggests the equilibrium position is pushed towards the products. Signup and view all the answers

What is the relationship between the total entropy change and the equilibrium constant?

Total entropy change can be used to explicitly calculate the equilibrium constant. Signup and view all the answers

In heterogeneous equilibria, what is the significance of involving different phases?

Solids and liquids do not appear in the expression for the equilibrium constant. Signup and view all the answers

What is true about the reaction quotient compared to the equilibrium constant?

The reaction quotient can predict the direction of the reaction before reaching equilibrium. Signup and view all the answers

Which scenario would lead to a shift in the equilibrium position according to Le Chatelier's Principle?

Increasing the temperature of an exothermic reaction. Signup and view all the answers

What does a very small value of the equilibrium constant suggest?

The reaction does not proceed to any measurable extent. Signup and view all the answers

When calculating equilibrium concentrations, which factor is not usually included in equilibrium expressions?

Concentrations of pure solids. Signup and view all the answers

What effect does increasing pressure have on a reaction at equilibrium involving an unequal number of gas moles?

It favors the side with fewer moles of gas. Signup and view all the answers

If the total entropy change for a reaction is positive, what can be inferred about the equilibrium constant?

The equilibrium constant is likely to be large. Signup and view all the answers

What is the primary factor that causes a change in the equilibrium constant, Kc?

Temperature Signup and view all the answers

Which types of species are included in the equilibrium expression?

Aqueous and gaseous substances Signup and view all the answers

For the reaction A + bB ⇌ cC + dD, which of the following represents the correct equilibrium expression?

Kc = [C]^c [D]^d / [A]^a [B]^b Signup and view all the answers

Which statement best describes homogeneous equilibria?

They involve reactants and products in the same phase. Signup and view all the answers

According to Le Chatelier's Principle, what will happen if the concentration of a reactant is increased in a system at equilibrium?

The reaction will favor the formation of products. Signup and view all the answers

What does the reaction quotient, Q, represent in a chemical reaction?

The ratio of the concentrations of products to reactants at any point. Signup and view all the answers

When solids are present in a chemical equilibrium, how are they treated in the equilibrium expression?

Their concentrations are considered constant and excluded from the expression. Signup and view all the answers

In a system at equilibrium, what effect does increasing temperature have on an exothermic reaction?

It shifts the equilibrium to the left, favoring reactants. Signup and view all the answers

Which of the following equations correctly reflects an equilibrium constant expression?

Kc = [C][D]/[A][B] Signup and view all the answers

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Description

Test your understanding of chemical equilibrium with this quiz covering key principles like equilibrium constant expressions, Le Chatelier's Principle, and the differences between heterogeneous and homogeneous equilibria. Questions also explore the significance of significant figures and the effects of temperature on equilibrium constants.