At equilibrium, the concentrations of the reactants and the products are generally not equal to each other.
Correct Answer
True
True. Equilibrium means the concentrations have stopped changing, not that they match; depending on K, the mixture may be mostly products, mostly reactants or anywhere in between.
Category: Dynamic Equilibrium
Question 2
A reversible reaction can reach equilibrium starting from a flask that contains only products.
Correct Answer
True
True. If only products are present, the reverse reaction runs first and forms reactants until the forward and reverse rates become equal. Equilibrium can be approached from either direction.
Category: Dynamic Equilibrium
Question 3
The equilibrium concentrations reached in a reaction depend on the starting amounts, although the value of K at that temperature does not.
Correct Answer
True
True. Different starting mixtures lead to different sets of equilibrium concentrations, but each set gives the same value of K when substituted into the equilibrium expression at that temperature.
Category: Dynamic Equilibrium
Question 4
For H2(g) + I2(g) ⇌ 2HI(g), changing the volume of the container does not shift the equilibrium.
Correct Answer
True
True. There are 2 moles of gas on each side, so compressing or expanding the mixture changes every concentration by the same factor and leaves Q equal to K. Volume changes shift only equilibria with unequal moles of gas on the two sides.
Category: Le Chatelier's Principle
Question 5
The magnitude of an equilibrium constant indicates how quickly a reaction reaches equilibrium.
Correct Answer
False
False. K describes the composition of the mixture at equilibrium, not the rate. A reaction with a very large K can still be extremely slow; speed is a matter of kinetics.
Category: Equilibrium Expressions
Question 6
When the reaction quotient Q equals the equilibrium constant K, the system is at equilibrium.
Correct Answer
True
True. K is the value Q takes at equilibrium. When Q = K, the forward and reverse rates are equal and there is no net change in the amounts of reactants or products.
Category: Reaction Quotient
Question 7
In the Haber process, ammonia is removed as it forms, which keeps shifting the equilibrium toward making more ammonia.
Correct Answer
True
True. Removing a product lowers Q below K, so the system responds by forming more product. Continuous removal of ammonia lets the process convert more nitrogen and hydrogen than a closed equilibrium would.
Category: Le Chatelier's Principle
Question 8
When K is close to 1, appreciable amounts of both reactants and products are present at equilibrium.
Correct Answer
True
True. A K near 1 means the product terms and reactant terms in the equilibrium expression are of similar size, so neither side dominates. Very large K values favor products and very small K values favor reactants.
Category: Equilibrium Expressions
Question 9
In the simplified convention used in general chemistry, equilibrium constants are reported without units.
Correct Answer
True
True. Equilibrium constants are formally based on activities, which are unitless, so K values are treated as dimensionless numbers even though they are calculated from molar concentrations or pressures.
Category: Equilibrium Expressions
Question 10
An equilibrium constant has a negative value when the reactants are favored.
Correct Answer
False
False. An equilibrium constant is a ratio of positive quantities, so it is always positive. When reactants are favored, K is a positive number less than 1.
Category: Equilibrium Expressions
Question 11
When water is the solvent in an aqueous equilibrium, its concentration is left out of the equilibrium constant expression.
Correct Answer
True
True. Water acting as the solvent is essentially a pure liquid whose relative concentration barely changes, so it is treated as 1 and omitted, just as pure solids and pure liquids are.
Category: Equilibrium Expressions
Question 12
At equilibrium, the rate constant of the forward reaction equals the rate constant of the reverse reaction.
Correct Answer
False
False. At equilibrium the forward and reverse rates are equal, but the rate constants usually are not. The ratio of the forward rate constant to the reverse rate constant equals K.
Category: Dynamic Equilibrium
Question 13
Raising the temperature of an exothermic reaction at equilibrium shifts the equilibrium toward the products.
Correct Answer
False
False. For an exothermic reaction, heat behaves like a product, so adding heat shifts the equilibrium toward the reactants and lowers K.
Category: Le Chatelier's Principle
Question 14
The equilibrium constant Kp is written using the molar concentrations of the gases in the reaction.
Correct Answer
False
False. Kp is written using the partial pressures of the gases. The constant written with molar concentrations is Kc.
Category: Equilibrium Expressions
Question 15
A reaction mixture with a reaction quotient of zero contains only products.
Correct Answer
False
False. Q has product terms in its numerator, so Q = 0 means no product is present yet; the mixture contains only reactants and the net reaction will run forward.
Category: Reaction Quotient
Question 16
Le Chatelier's principle states that a system at equilibrium responds to a stress by shifting in the direction that partly offsets that stress.
Correct Answer
True
True. For example, adding a reactant causes the system to consume some of it, and removing heat from an exothermic reaction causes it to produce more heat by shifting toward products.
Category: Le Chatelier's Principle
Question 17
A catalyst speeds up the forward reaction of an equilibrium but leaves the rate of the reverse reaction unchanged.
Correct Answer
False
False. A catalyst lowers the activation energy of both the forward and reverse reactions and speeds both of them, which is why it does not change the position of equilibrium.
Category: Le Chatelier's Principle
Question 18
The equilibrium constant is calculated from the concentrations present at the start of a reaction.
Correct Answer
False
False. K is calculated from the concentrations present once equilibrium is reached. The same expression applied to concentrations at any other moment, including the start, gives the reaction quotient Q.
Category: Equilibrium Calculations
Question 19
For 2A(g) ⇌ B(g) with Kc = 4.0, an equilibrium mixture that contains [A] = 0.50 M has [B] = 2.0 M.
Correct Answer
False
False. Kc = [B]/[A]^2, so [B] = 4.0 × (0.50)^2 = 4.0 × 0.25 = 1.0 M. The value 2.0 M comes from forgetting to square [A].
Category: Equilibrium Calculations
Question 20
Adding more of a pure solid reactant to a heterogeneous equilibrium shifts the equilibrium toward the products.
Correct Answer
False
False. A pure solid does not appear in the equilibrium expression, so adding more of it does not change Q and causes no shift, as long as some solid was already present.
Category: Le Chatelier's Principle