The Rate & Extent of Chemical Change

• signs of a reaction:

  • fizzing
  • change in temperature
  • a new texture
  • a new smell
  • a precipitate (forming a solid)
• rate of a reaction:

  • a measurable of how quickly a reactant is used up or a product is formed
• using mass:

  • rate of reaction (g/s) = mass of reactant loss or gained (g) / time
• using volume:

  • rate of reaction (cm/s) = volume of product gained (cm) / time
• • reactant particles must collide with each other
  • the particles must collide with enough energy for them to react (activation energy)
• main factors that effect the rate of chemical reactions:

  • surface area
  • temperature
  • concentration of solution/ pressure of gases
  • presence of a catalyst
• collision theory tells us there are two reasons why increasing the temperature increases the rate of reaction:

  • particles collide more often as they are moving faster
  • particles collide with more energy meaning more successful collisions
• ⇌

  • symbol of a reversible reaction
• A reversible reaction is one in which both the forward and backward reactions can take place
• To reach equilibrium, the reactants and products must be in a closed system. This means that the reactants and products can't escape
• endothermic reactions:

  • Heat energy is taken in from the surroundings
• exothermic reactions:

  • Heat energy is given out to the surroundings
• In a reversible reaction, if the forward reaction is exothermic, the backward reaction is endothermic
• If the position of equilibrium lies to the right, it means there are more products
• a closed system:

  • no reactants added
  • no products removed
• le chatelier's principle:

  • when a system is at equilibrium, any change you make to the system will result in the system opposing your change
• increasing temperature will make the reaction go in the endothermic direction
• decreasing temperature will make the reaction go in the exothermic direction
• endothermic:

  • takes in heat
  • temperature decrease
  • feel cold
• exothermic:

  • gives out heat
  • temperature increase
  • feels warm
• Le Chatalier's principle states that if pressure is increased, equilibrium will shift to decrease the pressure. This means that equilibrium will shift to the side will less moles of gas as these will contribute less pressure.