XI US Before exam - Ciayou

1.    In the same concentration, of the following compounds, which has the strongest acidic properties ?

• H₂S

• HCl

• H₂SO₄

• HF

This symbol indicates that a reaction is _____

• reversible

• irreversible

The equilibrium constant expression for the reaction BrF_5(g) —> Br_2(g) + F_2(g) is

• Kc = [Br₂] [F₂] / [BrF_5]

• Kc = [BrF₅]² / [Br₂][F₂]⁵

• Kc = [Br₂] [F₂]⁵ / [BrF₅]²

• Kc = 2[BrF₅]² / ([Br₂] × 5[F₂]⁵)

• Kc = [Br₂] [F₂]² / [BrF₅]⁵

Which is the correct equilibrium constant expression for the following reaction?

Fe₂O_3(s) + 3H_2(g) —> 2Fe_(s) + 3H₂O_(g)

• K = [H₂O]3 / [H₂]³

• K = [Fe₂O₃] [H₂]³ / [Fe]²[H₂O]³

• K = [Fe]²[H₂O]³ / [Fe_2O₃] [H₂]³

• K= [Fe] [H₂O] / [Fe₂O₃] [H₂]

• K = [H₂] / [H₂O]

The equilibrium between carbon dioxide gas and carbonic acid is very important in biology and environmental science. CO_2(g) + H₂O_(l) —> H₂CO3(aq)

Which one of the following is the correct equilibrium constant expression (Kc) for this reaction?

• Kc= 1/ [H₂CO₃]

• Kc= [CO₂]/ [H₂CO₃]

• Kc= [H₂CO₃] / [CO₂]

• Kc= [CO₂] [H₂O] / [H₂CO₃]

• Kc= [H₂CO₃] / [CO₂] [H₂O]

Which of the following changes will shift the position of the equilibrium to the left?

• Increasing the temperature of an exothermic reaction.

• Increasing the pressure of a reaction that has the same number of moles of gas on both sides

• Adding a catalyst to a reaction

• Adding more concentrations to the reactants

At equilibrium, the rate of the forward reaction is ________ the rate of the backward reaction

• Greater than

• Equal to

• Less than

Which of the following will never affect the position of an equilibrium?

• The temperature

• The pressure

• A catalyst

• The concentration of reactants

Hydrogen can be made by reacting carbon with steam:

C(s) + H₂O(g) ⇌ H₂(g) + CO(g)

How can the equilibrium concentration of hydrogen be increased?

• Increase the concentration of steam

• Increase the concentration of carbon monoxide

• Use less carbon in the reaction

• Increase the concentration of hydrogen

The thermal decomposition of calcium carbonate is reversible:

CaCO₃(s) ⇌ CaO(s) + CO₂(g)

What happens to the position of equilibrium when the pressure is increased?

• It does not change

• It moves to the left

• It moves to the right

• It stays constant