Untitled Quiz

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Questions and Answers

Which statement best defines a strong acid?

A strong acid can only be an Arrhenius acid.

A strong acid ionizes partially in water.

A strong acid does not produce H+ ions in water.

A strong acid ionizes completely in water. (correct)

According to the Brønsted-Lowry concept, what role does a base play in a proton-transfer reaction?

It donates a proton.

It produces hydroxide ions.

It accepts a proton. (correct)

It acts as a buffer solution.

What characterizes a heterogeneous reaction?

At least two different phases are involved. (correct)

Reactants and products are in the same physical state.

It proceeds in both forward and reverse directions.

It does not reach an equilibrium state.

Which of the following pairs represents a weak acid and a weak base?

CH3COOH and NH3 Signup and view all the answers

What theory describes acids as electron pair acceptors and bases as electron pair donors?

Lewis concept Signup and view all the answers

What is the primary limitation of the Arrhenius concept of acids and bases?

It cannot explain acid-base reactions in non-aqueous solutions. Signup and view all the answers

Which of the following reactions is classified as an acid-base reaction?

HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l) Signup and view all the answers

What is the ionization constant a measure of?

The strength of the acid or base in a solution. Signup and view all the answers

What is the expression for the ionization constant of acetic acid (Ka)?

$\frac{[CH_3COO^-][H_3O^+]}{[CH_3COOH]}$ Signup and view all the answers

In the self-ionization of water, what ions are produced?

H3O+ and OH− Signup and view all the answers

Which statement correctly describes the equilibrium constant (Kw) for water?

$Kw$ varies based on temperature Signup and view all the answers

According to Le Chatelier’s principle, what occurs when pressure is increased in a reaction with more gaseous products than reactants?

The equilibrium shifts toward the reactants Signup and view all the answers

What is the effect of increasing the temperature on an endothermic reaction?

Shifts the equilibrium toward the products Signup and view all the answers

If more O2 is added to the equilibrium reaction 2 SO3(g) ⇌ 2 SO2(g) + O2(g), what will be the effect?

The reaction shifts to the left Signup and view all the answers

What happens when O2 is removed from the system in the equilibrium 2 SO3(g) ⇌ 2 SO2(g) + O2(g)?

Shifts the equilibrium toward the products Signup and view all the answers

What is the equilibrium constant expression for the reaction 2 SO2(g) + O2(g) ⇌ 2 SO3(g)?

$K_c = \frac{[SO3]^2}{[SO2]^2[O2]}$ Signup and view all the answers

Study Notes

Chemical Equilibrium

Chemical equilibrium is a state where the forward and reverse reactions occur at the same rate.
The concentrations of reactants and products remain constant.
A reversible reaction involves the simultaneous conversion of reactants to products and products to reactants.
An irreversible reaction proceeds in one direction only.

Types of Chemical Reactions in Aqueous Solutions

Acid-base reactions: acid + base → salt + water
- Example: HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)
Oxidation-reduction reactions (Redox reactions): involve electron transfer
Precipitation reactions: result in the formation of a solid precipitate

Acids and Bases

Arrhenius concept:
- An acid releases H⁺ ions in water.
- A base releases OH⁻ ions in water.
- Example: HCl(aq) → H⁺(aq) + Cl⁻(aq)
- Example: NaOH(aq) → Na⁺(aq) + OH⁻(aq)
- Limitation: Some bases do not contain OH⁻.
Brønsted-Lowry concept:
- An acid is a proton (H⁺) donor.
- A base is a proton acceptor.
Lewis concept:
- An acid is an electron pair acceptor.
- A base is an electron pair donor.

Strength of Acids and Bases

Strong acids and bases ionize completely in water.
Examples of strong acids: HCl, HBr, HI, HNO₃, H₂SO₄, HClO₄
Examples of strong bases: LiOH, NaOH, KOH, Ca(OH)₂, Sr(OH)₂, Ba(OH)₂

Equilibrium Constant Law

Equilibrium constant (Kc) is a measure of the ratio of products to reactants at equilibrium.
A homogeneous reaction involves all reactants and products in the same phase.
A heterogeneous reaction involves reactants and products in at least two different phases.

Weak Acids and Bases

Weak acids and bases ionize to a limited extent in water.
Examples: CH₃COOH, NH₃
Acid or base ionization constant (Ka or Kb) measures the strength of the acid or base.
The ionization constant is given by the equilibrium expression.

Self-Ionization of Water

Water can act as both an acid and a base (self-ionization).
Water dissociates into H₃O⁺ and OH⁻ ions.
The equilibrium constant for the self-ionization of water is Kw.
Kw = [H₃O⁺][OH⁻]

Equilibrium Constant Equation

Example: 2 SO₂(g) + O₂(g) ↔ 2 SO₃(g)
Kc = [SO₃]² / [SO₂]²[O₂]

Le Chatelier's Principle

A change in conditions of a system at equilibrium shifts the equilibrium to counteract the change.
- Change in concentration of a reactant or product
- Change in temperature
- Change in pressure (for gaseous reactions)

Predict the effect of the changes

Increasing the temperature: shifts the equilibrium towards the products in endothermic reactions.
Increasing the pressure: shifts the equilibrium towards the side with fewer moles of gas.
Adding more O₂: shifts the equilibrium towards the reactants.
Removing O₂: shifts the equilibrium towards the products.