Equilibrium Unit 12

When a chemical reaction is at equilibrium, the concentration of each reactant and the concentration of each product must be (1) constant (2) variable (3) equal (4) zero

An open flask is half filled with water at 25°C. Phase equilibrium can be reached after (1) more water is added to the flask (2) the flask is stoppered (3) the temperature is decreased to 15°C (4) the temperature is increased to 35°C

Given the equation representing a system at equilibrium: N2(g) + 3H2(g) <==> 2NH3(g) Which statement describes this reaction at equilibrium? (1) The concentration of N2(g) decreases. (2) The concentration of N2(g) is constant. (3) The rate of the reverse reaction decreases. (4) The rate of the reverse reaction increases.

For a reaction at equilibrium, which change can increase the rates of the forward and reverse reactions? (1) a decrease in the concentration of the reactants (2) a decrease in the surface area of the products (3) an increase in the temperature of the system (4) an increase in the activation energy of the forward reaction

Which type of equilibrium exists in a sealed flask containing Br2(ℓ) and Br2(g) at 298 K and 1.0 atm? (1) static phase equilibrium (2) static solution equilibrium (3) dynamic phase equilibrium (4) dynamic solution equilibrium

According to Table I, which equation represents a change resulting in the greatest quantity of energy released? (1 ) 2C(s) + 3H2 (g) à C2H6(g) (2) 2C(s) + 2 H2 (g) àC2H4(g) (3) N2 (g) + 3 H2 (g) à2NH3(g) (4) N2 (g) + O2(g) à2NO(g)

Which statement describes a reversible reaction at equilibrium? (1) The activation energy of the forward reaction must equal the activation energy of the reverse reaction. (2) The rate of the forward reaction must equal the rate of the reverse reaction. (3) The concentration of the reactants must equal the concentration of the products. (4) The potential energy of the reactants must equal the potential energy of the products.

In terms of entropy and energy, systems in nature tend to undergo changes toward (1 ) lower entropy and lower energy (2) lower entropy and higher energy (3) higher entropy and lower energy (4) higher entropy and higher energy

Given the equation representing a reaction at equilibrium : 2SO2(g) + O2(g) ==> 2SO3(g) + heat Which change causes the equilibrium to shift to the right? (1) adding a catalyst (2) adding more O2(g) (3) decreasing the pressure (4) increasing the temperature

Some solid KNO3 remains at the bottom of a stoppered flask containing a saturated KNO3(aq) solution at 22°C, Which statement explains why the contents of the fl ask are at equilibrium? (1) The rate of dissolving is equal to the rate of crystallizaion, (2) The rate of dissolving is greater than the rate of crystallization . (3) The concentration of the solid is equal to the concentration of the solution. (4) The concentration of the solid is greater than the concentration of the solution

Given the equation representing a closed system: N2O4(g) <=> 2NO2(g) Which statement describes this system at equilibrium? (1) The volume of the NO2(g) is greater than the volume of the N2O4(g) (2) The volume of the NO2(g) is less than the volume of the N2O4(g) (3) The rate of the forward reaction and the rate of the reverse reaction are equal (4) The rate of the forward reaction and the rate of the reverse reaction are unequal

Given the equation representing a system at equilibrium: 2SO2(g) + O2(g) <==> 2SO3(g) At equilibrium, the concentration of (1) SO2(g) must equal the concentration of SO3(g) (2) SO2(g) must be constant (3) O2(g) must equal the concentration of SO2(g) (4) O2(g) must be decreasing

The entropy of a sample of CO2 increases as the CO2 changes from (1) gas to liquid (3) liquid to solid (2) gas to solid (4) solid to gas

Which two factors must be equal when a chemical reaction reaches equilibrium? (1) the concentration of the reactants and the concentration of the products (2) the number of reactant particles and the number of product particles (3) the rate of the forward reaction and the rate of the reverse reaction (4) the mass of the reactants and the mass of the products

Given the equation representing a phase change at equilibrium: H2O(s) <==>H2O(l) Which statement describes this equilibrium? (1) The H2O(s) melts faster than the H2O(l) freezes. (2) The H2O(l) freezes faster than the H2O(s) melts. (3) The mass of H2O(s) must equal the mass of H2O(l). (4) The mass of H2O(l) and the mass of H2O(s) each remain constant.

Given the equation representing a system at equilibrium: N2(g) + 3H2(g)<==>2NH3(g) + energy Which changes occur when the temperature of this system is decreased? (1) The concentration of H2(g) increases and the concentration of N2(g) increases. (2) The concentration of H2(g) decreases and the concentration of N2(g) increases. (3) The concentration of H2(g) decreases and the concentration of NH3(g) decreases. (4) The concentration of H2(g) decreases and the concentration of NH3(g) increases.

Given the equation representing a reaction at equilibrium: H2(g) + I2(g) + heat--> 2HI(g) Which change favors the reverse reaction? (1) decreasing the concentration of HI(g) (2) decreasing the temperature (3) increasing the concentration of I2(g) (4) increasing the pressure

Which 1-mole sample has the least entropy? (1) Br2(s) at 266 K (3) Br2(l) at 332 K (2) Br2(l) at 266 K (4) Br2(g) at 332 K

Given the equation representing a reaction at equilibrium: NH3(g) + H2O(l) ==>NH4+(aq) + OH-(aq) The H+ acceptor for the forward reaction is (1) H2O(l) (3) NH4+(aq) (2) NH3(g) (4) OH-(aq)

Given the equation representing a system at equilibrium: H2O(s)<==>H2O(l) At which temperature does this equilibrium exist at 101.3 kilopascals? (1) 0 K (3) 32 K (2) 0°C (4) 273°C

Which statement must be true when solution equilibrium occurs? (1) The solution is at STP. (2) The solution is supersaturated. (3) The concentration of the solution remains constant. (4) The masses of the dissolved solute

Given the equation representing a reaction at equilibrium: N2(g) + 3H2(g)==> 2NH3(g) + energy Which change causes the equilibrium to shift to the right? (1) decreasing the concentration of H2(g) (2) decreasing the pressure (3) increasing the concentration of N2(g) (4) increasing the temperature

Which statement must be true for any chemical reaction at equilibrium? (1) The concentration of the products is greater than the concentration of the reactants. (2) The concentration of the products is less than the concentration of the reactants. (3) The concentration of the products and the concentration of the reactants are equal. (4) The concentration of the products and the concentration of the reactants are constant.

Which balanced equation represents a phase equilibrium? (1) H2(g) + I2(g)<==> 2HI(g) (2) 2NO2(g) <==> N2O4(g) (3) Cl2(g) <==> Cl2(l) (4) 3O2(g)<==> 2O3(g)

Given the system at equilibrium: 2POCl3(g) + energy <==> 2PCl3(g) + O2(g) Which changes occur when O2(g) is added tothis system? (1) The equilibrium shifts to the right and the concentration of PCl3(g) increases. (2) The equilibrium shifts to the right and the concentration of PCl3(g) decreases. (3) The equilibrium shifts to the left and the concentration of PCl3(g) increases. (4) The equilibrium shifts to the left and the concentration of PCl3(g) decreases

A chemical reaction is at equilibrium. Compared to the rate of the forward reaction, the rate of the reverse reaction is (1) faster and more reactant is produced (2) faster and more product is produced (3) the same and the reaction has stopped (4) the same and the reaction continues in both directions

Given the reaction at equilibrium: N2(g) + 3H2(g) -->2NH3(g) + 91.8 kJ What occurs when the concentration of H2(g) is increased? (1) The rate of the forward reaction increases and the concentration of N2(g) decreases. (2) The rate of the forward reaction decreases and the concentration of N2(g) increases. (3) The rate of the forward reaction and the concentration of N2(g) both increase. (4) The rate of the forward reaction and the concentration of N2(g) both decrease.

Which factors must be equal in a reversible chemical reaction at equilibrium? (1) the activation energies of the forward and reverse reactions (2) the rates of the forward and reverse reactions (3) the concentrations of the reactants and products (4) the potential energies of the reactants and products

Given the reaction system in a closed container at equilibrium and at a temperature of 298 K: N2O4(g) <==>2NO2(g) The measurable quantities of the gases at equilibrium must be (1) decreasing (3) equal (2) increasing (4) constant

Which statement must be true about a chemical system at equilibrium? (1) The forward and reverse reactions stop. (2) The concentration of reactants and products are equal. (3) The rate of the forward reaction is equal to the rate of the reverse reaction. (4) The number of moles of reactants is equal to the number of moles of product.

Given the equilibrium reaction at STP: N2O4(g) <==> 2 NO2(g) Which statement correctly describes this system? (1) The forward and reverse reaction rates are equal. (2) The forward and reverse reaction rates are both increasing. (3) The concentrations of N2O4 and NO2 are equal. (4) The concentrations of N2O4 and NO2 are both increasing.

Which statement correctly describes a chemical reaction at equilibrium? (1) The concentrations of the products and reactants are equal. (2) The concentrations of the products and reactants are constant. (3) The rate of the forward reaction is less than the rate of the reverse reaction. (4) The rate of the forward reaction is greater than the rate of the reverse reaction.

Given the equilibrium reaction in a closed system: H2(g) + I2(g) + heat-->2 HI(g) What will be the result of an increase in temperature? (1) The equilibrium will shift to the left and [H2] will increase. (2) The equilibrium will shift to the left and [H2] will decrease. (3) The equilibrium will shift to the right and [HI] will increase. (4) The equilibrium will shift to the right and [HI] will decrease.

Which type or types of change, if any, can reach equilibrium? (1) a chemical change, only (2) a physical change, only (3) both a chemical and a physical change (4) neither a chemical nor a physical change

A catalyst is added to a system at equilibrium. If the temperature remains constant, the activation energy of the forward reaction (1) decreases (2) increases (3) remains the same

Physical equilibrium

The only factor that can change keq is

If temp increases

If temp decreases

Increase in concentration

Decreases in concentration

If press. increases

If press decreases

(aq) has a higher entropy than