Chemical Equilibrium and Gibbs Energy

• Reversible reactions include: N2(g) + 3H2(g) ⇌ 2NH3(g)

Equilibrium Constants

• At 500°C, Kp is 1.44 × 10-5 when partial pressures are measured in atmospheres
• Determine the corresponding Kc using concentrations in mol L-1

Equilibrium Shifts in Closed Containers

• In a closed container with N2O4(g) ⇌ 2NO2(g) at a fixed temperature, halving the volume affects equilibrium
• Kp= equilibrium constant
• α = degree of dissociation

Reaction Extent and Kc

• The extent of a reaction depends on KC
• If KC > 103, products predominate, proceeding nearly to completion
• If KC < 10-3, reactants predominate, rarely proceeding
• If KC is between 10-3 and 103, appreciable concentrations of both reactants and products are present

Gibbs Energy

• The standard Gibbs energy change (ΔG) relates to the reaction quotient (Q) and equilibrium constant (K)
• Use the equation: ΔG = ΔG° + RT In Q

Reaction Quotient (Qc)

• For H2(g) + I2(g) ⇌ 2HI(g), calculate Qc using molar concentrations
• Qc indicates the direction a reaction must shift to reach equilibrium

Production of Ammonia

• In N2(g) + 3H2(g) ⇌ 2NH3(g) with ΔH = -92.38 kJ mol-1, low temperature influences ammonia production
• The reaction is exothermic

Equilibrium Constant Expressions

• For 4NH3(g) + 5O2(g) ⇌ 4NO(g) + 6H2O(g), K is expressed in terms of product and reactant concentrations

Kc Units

• The unit of KC for CaCO3(s) ⇌ CaO(s) + CO2(g)can be expressed as mol L-1

Partial Pressures and Kp

• For C(s) + CO2(g) ⇌ 2CO(g). Kp can be calculated from the partial pressures of CO2 and CO at equilibrium

Acid-Base Chemistry

• According to Bronsted-Lowry theory, a conjugate acid-base pair involves proton transfer
• NH3(aq) + H2O(l) ⇌ NH4+(aq) + OH-(aq)

Dissociation Constants

• Ka indicates acid strength
• The correct order of increasing base strength refers to the bases CN-, F-, and NO2-

Ammonia Ionization

• In a 0.01 M ammonia solution with 5% ionization, determine the concentration of OH- ions

pH Calculation

• Mix 2.5 moles KCN and 2.5 moles HCN in 500 mL to determine the pH
• Use the pKa of HCN = 9.30

NaOH Solutions

• Dissolving 2g of NaOH in 1L of water yields a solution with a pH > 7

Molar Solubility

• For a salt like zirconium phosphate with molecular formula (Zr)3(PO4)4, calculate molar solubility (S)

Solubility of Silver Chloride

• Solubility (S)1, S2, S3, and S4 of AgCl exist in different solutions
• In water
• In 0.01 M CaCl2
• In 0.01 M NaCl
• In 0.05 M AgNO3, at a certain temperature, can be used to establish a correct order

Lewis Base Identification

• Know what can act as a Lewis base

Degree of Dissociation

• Degree of dissociation of a 0.1 M aqueous solution of a weak acid HA with Ka(HA) = 10-7
• Ka(HA) = 10−7.

Kb and Ka Relationship

• Can determine Ka for the NH4+ ion, if Kb for NH3 is 1.8 × 10-5

Kp and Kc Comparison

• Understand the relationship between Kp and Kc
• N2O4 ⇌ 2NO2
• N2 + 3H2 ⇌ 2NH3
• H2 + I2 ⇌ 2HI
• CO + H2O ⇌ CO2 + H2

Solubility Product

• The equilibrium expression for the reaction P4(s) + 5O2(g) ⇌ P4O10(s) can be correctly represented as KC = 1/[O2]5

Barium Hydroxide Solutions

• Determine pH of .001 M Ba(OH)2

Salt Nature

• Understand what does not show its correct nature mentioned against it?
• KBr has a neutral solution
• NaCN has an acidic nature
• NH4NO3 solutions have acidic solution
• KF solutions are considered basic

pH calculations

• In five litres of water, add 0.05 moles of NaOH
• Calculate the pH of the solution

Match Reactions

• Match the reaction A) Fe(OH)3 B) Ag2CrO4 C) CH3COOAg, and D) Ca3(PO4)2

• Match the following Ksp i) Ksp= s2 ii) Ksp = 27 s4 iii) Ksp =108 s5 and iv)K sp = 4s3

• Buffer solutions are a mixture of a weak acid together with a base

• Some reactions undergo only cationic hydrolysis

• Others undergo reactions and a matching Ksp= 4s3

pH of Mixed Solutions

• Equal volumes of solutions at pH10 and pH 12 yields a resulting solution of pH 11.7

Nickel Hydroxide Solutions

• If the solubility product of Ni(OH)2 is 2 x 10-15, calculate the resulting molar solubility of aqueous of 0.2 M NaOH

Degree of Dissociation Calculation

• In a reaction PCl5 ⇌ PCl3 + Cl2, determine the total moles at equilibrium
• The degree of dissociation of PCl5 is 30 %

Correct Relations

• ΔG = gibbs energy
• K represents, the constant of a reaction
• To solve for Q, determine the reaction quotient for a product

Reaction Statements

• Reaction quotient has a value at point A
• [N2O4] = [NO2] = equal to 0.1 M
• Equilibrium where K = Q point D or F

Buffer Solutions

• Buffer solutions contain CH3COONa and CH3COOH

Silver Chloride Solubility

• Know the solubility of silver chloride (AgCl) when the Ksp(AgCl) = 1.8 x 10^-10 contains a (10^-2)M NaCl mixture

Le Chatelier’s Principle

• In the reaction: N2(g) + 3H2(g) <=>2NH3 + Heat, one can maintain equilibrium in shifts in forward direction with the appropriate concentration and tempurature

Graphite Production

• With the graphite equilibrium will be reached once KP will be shown by atm

Molar solutions mixing

• Know Kp is not equal to KC in chemical equations

Equilibrium Mixture Equations

• Know at which point N2O4 equals 2NO2 is important for the reactions and chemical mixtures