Reversible reactions & Equilibria

What happens in a reversible reaction?

The products can react to form the original reactants.

How can the direction of a reversible reaction be changed?

By changing the conditions.

What is the equation for the dehydration of hydrated copper(II) sulfate?

Anhydrous CuSO₄ + H₂O ⇌ Hydrated CuSO₄

What happens when water is added to anhydrous copper(II) sulfate?

It turns blue as it forms hydrated copper(II) sulfate.

What happens when hydrated copper(II) sulfate is heated?

It loses water and turns white (anhydrous CuSO₄).

What is the equation for the effect of heat on ammonium chloride?

NH₄Cl ⇌ NH₃ + HCl

What happens when ammonium chloride is heated?

It decomposes into ammonia (NH₃) and hydrogen chloride (HCl) gases.

What is dynamic equilibrium?

When the forward and reverse reactions occur at the same rate in a closed system.

What remains constant at dynamic equilibrium?

The concentrations of reactants and products.

Why does a catalyst not affect the position of equilibrium?

It speeds up both the forward and reverse reactions equally.

How does increasing temperature affect equilibrium?

It shifts in the direction of the endothermic reaction.

How does decreasing temperature affect equilibrium?

It shifts in the direction of the exothermic reaction.

If the forward reaction is exothermic, how does increasing temperature affect yield?

It decreases the yield of the product.

How does increasing pressure affect equilibrium?

It shifts to the side with fewer moles of gas.

How does decreasing pressure affect equilibrium?

It shifts to the side with more moles of gas.

In the Haber process (N₂ + 3H₂ ⇌ 2NH₃), how does increasing pressure affect equilibrium?

It shifts to the right (towards ammonia) because there are fewer gas molecules.

Why do covalent compounds not conduct electricity?

They do not have free electrons; the electrons are shared in covalent bonds.

When do ionic compounds conduct electricity?

When molten or in aqueous solution because the ions are free to move.

Which ions move to the cathode (-) during electrolysis?

Positively charged ions (cations).

Which ions move to the anode (+) during electrolysis?

Negatively charged ions (anions).

What is produced at the cathode in electrolysis of aqueous solutions?

Hydrogen gas (H₂) unless the metal is less reactive than hydrogen. (If the metal is less reactive, the metal is deposited instead.)

What is produced at the anode in electrolysis of aqueous solutions?

Oxygen gas (O₂) unless halide ions (Cl⁻, Br⁻, I⁻) are present. (If halide ions are present, the halogen is produced instead.)

What happens during electrolysis of sodium chloride solution?

H₂ gas at the cathode Cl₂ gas at the anode

What happens during electrolysis of copper(II) sulfate solution?

Copper (Cu) at the cathode Oxygen (O₂) at the anode

What happens during electrolysis of acidified water (H₂SO₄)?

H₂ gas at the cathode. O₂ gas at the anode.

What happens during electrolysis of molten lead(II) bromide?

Lead (Pb) at the cathode. Bromine (Br₂) at the anode.

What happens at the cathode in terms of oxidation and reduction?

Reduction occurs (gain of electrons)

What happens at the anode in terms of oxidation and reduction?

Oxidation occurs (loss of electrons).

What is the anode made of in electrolysis of copper sulfate?

Impure copper.

What is the cathode made of in electrolysis of copper sulfate?

Pure copper.

What happens to copper ions during electrolysis of copper sulfate?

Cu²⁺ ions move to the cathode, gain electrons, and become pure copper.

What happens to impurities in the anode?

They form sludge below the anode.