Chem C6

• If a solid sample is a desired end product, is it best to heat it in an open or closed furnace?

  An open furnace, as it allows the gas to escape, which helps drive the reaction to completion, ensuring a higher yield of the solid
• Explain Max enthalpy


  refers to the state where a system has absorbed the most heat, or stored the most amount of energy. delta H is positive
• explain minimum enthalpy 


  refers to the state where a system has released the most or stored the least amount of energy. Delta H is negative
• What is minimum entropy 


  the state of a system where it achieves the lowest level of disorder or randomness, characterised by the fewest number of microstates
• What is maximum entropy

  refers to the state of a system where it achieves the highest level of randomness or disorder.
• in an endothermic reaction, would the reactants of products have stronger bonds?

  reactants: the reaction required more energy to break the bonds of the reactants than is released when the products are formed. - results in a net absorption of energy
• in an exothermic reaction, would the reactants of products have stronger bonds?

  products: as the reaction is exothermic, there is more energy released than required to break the weak bonds in the reaction.
• According to L.C.P how can volume changes affect equilibrium

  Aqueous: when H2O is added to an aq solution, the conc. of all dissolved molecules/ions immediately decreases - this shifts equilibrium to the side with more dissolved species

  Gas:

  Increase in volume: decreases pressure, causing equilibrium to shift towards the side with the most gas molecules.

  decrease in volume: increases pressure, causing equilibrium to shift towards the side with the least gas molecules.
• What is a conjugate acid-base pair?


  An acid and a base that only differ in the absence/presence of a proton such as HX and X-
• Explain strength vs. concentration

  Strength: determined by the ability to dissociate into ions in an aqueous solution.

  concentration: refers to the amount of an acid or base dissolved in H2O.

  strong does not equal concentrated and weak does not equal dilute
• what is the bronstead-lowry base

  a substance that readily accepts protons
• what is a bronstead lowry acid

  a substance that readily donates protons
• according to L.C.P. how does adding a catalyst affect equilibrium?

  increases the rate of the forward + reverse reaction to the same extent, therefore equilibrium is not affected
• According to L.C.P how does temperature affect equilibrium?

  endothermic: increase favours forward reaction, and decrease favours reverse reaction

  Exothermic: increase favours reverse reaction, and decrease favours forward reaction
• According to L.C.P, how can we disturb equilibrium?

  • changing concentration (removing/adding products)
  • changing the volume
  • changing the pressure
  • changing the temp
• what are the four main influences that affect rates of reaction?

  • surface area
  • concentration/pressure
  • temperature
  • presence of a catalyst
• what happens to the rate of reaction when temp rises?

  the rate typically increases as higher temps increase the kinetic energy of molecules, leading to more frequent and energetic collisions. - helps more molecules overcome the Ea barrier resulting in a faster reaction rate
• what happens when Q<K


  the current ratio of products to reactant is less than at equilbrium and therefore the system shifts to the right

  • rate of the forward reaction is temporarily greater than the rate of the reverse reaction
  • products increase and reactants decrease until equilibrium is reached
• what does a small Kc value signify?

  That there is a larger qty of reactants than products at the point of equilibrium, therefore the reaction only proceeds to a small extent. - equilibrium lies to the left.
• What happens to the rate of reaction when temp decreases?

  The reaction rate generally decreases. this is because lower temps result in fewer and less energetic molecular collisions, reducing the likelihood of surpassing the activation energy barrier required for the reaction to proceed.
• What happens to the rate of reaction when a catalyst is added?

  Reaction rate increases - this is because catalysts provide an alternative pathway with a lower Ea for the reaction, allowing more reactant moleculed to successfully collide and react. - importantly, the catalysts itself is not consumed in the reaction and can be used repeatedly.
• How can you measure rates of reaction?

  • change in mass
  • change in volume (constant pressure)
  • change in pressure (constant volume)
  • change in colour intensity
• What is the Haber process?


  An industrial process where H2 and N2 gases are converted to ammonia using a catalyst or powdered iron.
• When does a system reach chemical equilibrium?

  occurs when the rate of the forward reaction is equal to the rate of the reverse reaction.
• What does a large Kc value signify?

  that there is a larger products qty than reactants at equilibrium - the position of equilibrium shifts to the right
• What happens when Q>K


  the current ratio of products to reactants is more than at equilibrium and the system shifts to the left

  • the rate of the reverse is temporarily greater than the forward reaction
  • reactants increase and products decrease until equilibrium is reached
• According to L.C.P, what happens when a chemical specie is removed/added?

  Adding more reactants/removing some of the products means Q ≠ Kc and thus shifts the point of equilibrium to the right - products will increase and reactants will decrease

  Adding more products/removing some reactants also means Q ≠ Kc and therefore shifts the position of equilibrium to the left. - products will decrease and reactants will increase
• What happens to the rate of reaction when the surface area of solids increases?

  By crushing a solid into smaller parts, more particles are present at the surface. Frequency of collisions between the particles and other reactant particles increases and reaction occurs more rapidly
• What happens to the rate of reaction when the conc. of reactants is increased?

  With more particles moving randomly in a given volume of a solution, the frequency of collisions increases therefore the rate of reaction increases.

  increasing the pressure of gases raises the conc. of gas molecules, causing more frequent particle collisions, therefore the rate of reaction increases.
• According to L.C.P how does a change in pressure affect equilibrium?

  increasing pressure favours the side with the least number of particles

  Decreasing pressure favours the side with the most particles
• What happens to equilibrium when an inert gas is added?

  Adding an inert gas does not affect equilibrium

  • no change in conc despite the change in pressure
  • no change in the position of equilibrium