PMT flashcards chapter 19

• What does it mean when a reaction is at equilibrium?

  The rate of forward and reverse reactions are equal
• What are the methods that can be used to measure equilibrium?

  • Measure change in colour or intensity using colorimeter
  • Use pH probe
  • Measure electrical conductivity
  • Titration for slow equilibrium changes
• What does mole fraction mean?

  The amount of a given component in a mixture
• What is the equation used to calculate mole fraction?

  Mole fraction = moles of substance A / total moles
• What does partial pressure mean?

  The pressure exerted by a single species
• What is the symbol for partial pressure?

  P
• What is the equation used to calculate partial pressure?

  Partial pressure = mole fraction x total pressure
• What is the relationship between concentration of a substance and its partial pressure?

  Concentration is proportional to partial pressure
• What are the 3 common units of pressure used in chemistry?

  • Pascals
  • Atmospheres
  • Newtons per square metre
• What type of brackets are used in Kc expressions?

  Square brackets
• What type of brackets are used in Kp expressions?

  Round brackets
• How do you calculate Kp for the reaction aA (g) + bB (g) ⇌ cC (g) + dD (g)?

  Use the equilibrium expression for Kp

  
• What is the symbol of the equilibrium constant?

  K
• How do you calculate the units for Kp?

  • Write out units for partial pressures
  • Arrange as in Kp equation
  • Cancel out/multiply together
  • Usually in Pa, kPa, atm
• What does it mean when K is greater than 1?

  Reaction favours products
• What does it mean when K is less than 1?

  Reaction favours reactants
• What is the effect of increasing temperature on K?

  Equilibrium shifts to endothermic direction
• What is the effect of decreasing temperature on K?

  Equilibrium shifts to exothermic direction
• What is the only factor that affects K?

  Temperature
• What is the effect of increasing temperature on K for a forward endothermic reaction?

  K increases as temperature increases
• What is the effect of increasing temperature on K for a forward exothermic reaction?

  K decreases as temperature increases
• What effect does a catalyst have on K?

  Catalysts do not affect the position of equilibrium