c6: the rate and extent of chemical change

• How is the rate of reaction calculated?

  Rate of reaction = amount of reactant used or product formed / time
• What is the formula for rate of reaction in moles?

  Rate of reaction (mol/s) = moles of reactant used or product formed / time
• What are the various units for rate of reaction?

  g/s, cm3/s, mol/s
• What is a common way to express rate of reaction?

  Generally, mass/time, volume/time, moles/time
• What are three common ways of measuring rate of reaction?

  • Loss in mass of reactants
  • Volume of gas produced
  • Time for a solution to become opaque
• How do you measure the rate by monitoring mass loss?

  Place the reaction flask on a balance. in these reactions, a gas is given off

  so record mass decrease over time
• How do you measure the rate by monitoring the volume of gas?

  Connect a gas syringe to a flask and measure gas volume over time
• How do you measure the rate by monitoring the disappearance of a cross?

  Mark a cross on a paper and put reaction flask on the cross.

  mix reagents and time how long it takes for a cloudy mixture to conceal a cross
• How do you find the rate of reaction at time t from a graph?

  Find the tangent at time t and calculate its gradient
• What are five factors affecting the rate of a chemical reaction?

  Concentration, pressure, surface area, temperature, catalysts
• What is the collision theory?

  Chemical reactions occur when particles collide with sufficient energy
• How does increasing temperature affect the rate of reaction?

  As T increases, kinetic energy of particles increase, more energetic collisions + move faster so they collide more frequently
• How does increasing concentration affect the rate of reaction?

  Conc. increases = faster reaction

  More reactants = more frequent collisions
• How does increasing pressure of a gas affect the rate of reaction?

  Higher pressure increases the number of gas molecules in a volume

  same as conc increase
• How does increasing surface area affect the rate of reaction?

  
  

  Smaller pieces of solid reactants increase collision frequency
• What is a catalyst and how does it work?

  A catalyst speeds up reactions by providing a lower activation energy pathway
• What is an enzyme?

  An enzyme is a biological catalyst
• What is a reversible reaction?

  A reversible reaction can produce original reactants from products
• When is dynamic equilibrium reached?

  When forward and reverse reactions occur at the same rate
• What is Le Chatelier’s Principle?

  Systems at equilibrium respond to counteract changes
• How does changing the concentration of reactants and products affect equilibrium?

  Changing concentration shifts equilibrium until a new balance is reached
• How does changing temperature affect the position of equilibrium?

  Increasing temperature favors endothermic reactions and decreases exothermic products
• How does changing pressure affect the position of equilibrium?

  Increasing pressure shifts equilibrium towards fewer gas molecules
• How does a catalyst affect the position of equilibrium?

  A catalyst has no effect on the position of equilibrium