Kinetics

• CH4(g) + H2O(g) CO(g) + 3H2(g) ΔH = +206 kJ mol−1

  What temp should be used to obtain highest yield of hydrogen?

  High temp as the forward reaction is endothermic. At high temps, the position of equilibrium shifts in the endothermic way to oppose increase.
• Why is operating at high pressure used in industries?

  Increases rate of reaction. Particles are packed closer, so increased collision frequency.
• Why is a catalyst more effective when coated onto unreactive honeycomb?

  Increased surface area, so more successful collisions.
• CO(g) + H2O(g) CO2(g) + H2(g) ΔH = −41 kJ mol−1

  How would a decrease in pressure affect the yield of hydrogen?

  No effect as there is equal moles on either sides of the equation.
• What does the area under Maxwell-boltzmann curve respresent?

  The total no. of particles.
• How is the forward/backward rate of reaction are related at equilibrium?


  Both forward/backward reaction is equal
• Define dynamic?


  Both forward and backward reaction occur at the same time.
• Why does the maxwell curve start at the origin?

  There are no particles with 0 energy.
• How does a catalyst increase the rate of reaction?

  It provides an alternative pathway by lowering the activation energy.
• Carboxylic acid is very expensive and ethanol is inexpensive. In the manufacture of this ester, the mole ratio of carboxylic acid to ethanol used is 1 to 10 rather than 1 to 1. Why is this ratio used?


  So the product of the ester increases as the position of the equilibrium shifts to the right to oppose the increase of moles of ethanol.
• H2SO4(aq) + Mg(s) > MgSO4(aq) + H2(g)

  When measuring the rate of reaction, what should the student use?

  Measure the volume of gas produced using a gas syringe.

  Or mass of container and contents using a balance.
• What condition other than temperature and pressure would need to be kept constant when measuring the change in rate of reaction?

  Mass/surface area of the metal.
• Draw a diagram to show how the student could separate the magnesium hydroxide from the reaction mixture?

  Conical flask.

  Buchner funnel.

  Filter paper.

  
• What method could the student use for removing soluble impurities from the sample that has been separated?

  Wash with water.
• Why does the rate of reaction decrease with a decrease in temp?

  As fewer particles have sufficient energy to react. Less successful collisions.
• Why did the student did not obtain a straight line?

  As concentration increases, the temp increases. This means more successful collisions in a given time, which increases the rate of reaction.

  
• Why it is important to clean the surface of a magnesium ribbon when investigating the rate of its reaction with hydrochloric acid?

  As the magnesium was coated with an oxide. The corrosion product needs to be removed before magnesium can react.
• Magnesium ribbon reacts with hot water. Heated magnesium ribbon reacts with steam. State two differences between these reaction?

  Reacts faster with steam than hot water.

  Hot water produces a mg hydroxide, steam produces mg oxide.
• Why is the reactions of magnesium and calcium with dilute sulfuric acid different?

  MgSO4 is soluble, where as CaSO4 is only slightly soluble. This is due to the CaSO4 coating on the surface of calcium, which prevents further reaction with the acid.
• Draw a diagram to show the apparatus that you would use to collect and measure the volume of the oxygen formed?

  Stoppered flask with side arm.

  Gas syringe.

  
• How could you use your results from a gas syringe to determine the initial rate of reaction?

  Plot a graph of volume of oxygen vs time.

  Determine the slope of the graph at the beginning.
• Define the rate of reaction?

  Amount of substance formed in a given time.
• What has happened to the rate of reaction at W?

  At W the rate is 0. The reaction is complete. Reactant has been all used up.

  
• Why does at a fixed temperature, the rate of this reaction doubles when the concentration of the hydrochloric acid doubles?

  As there is twice as many particles, so double the collision frequency.
• Define the activation energy?

  The minimum amount of energy for a reaction to occur.
• Write an equation for the reaction of barium with water?

  Ba + 2H2O > Ba(OH)2 + H2
• Write the simplest ionic equation for the reaction of barium and sodium sulfate?

  Ba2+ + SO42- > BaSO4

  Forms a white ppt.
• Explain one use of BaSO4 in medicine and why it is possible given that solutions containing barium ions are poisonous?

  Barium meal.

  BaSO4 is insoluble.
• State le chateliers principle?

  If a factor is changed that affects equilibrium, the position of equilibrium shifts to oppose the change.
• Define a catalyst and how it works?

  A substance that speeds up a reaction but is chemically unchanged.

  Provides an alternative route that lowers the activation energy.
• Whats a risk using a hand-warmer containing sodium hydroxide and hydrochloric acid?

  Container splitting and releasing corrosive chemicals.
• Write an equation for this reaction between iron and oxygen to form iron(lll) oxide?


  4Fe + 3O2 → 2Fe2O3
• Describe the two steps that you would take to make the sodium thiosulfate hand-warmer ready for re-use?

  Heat to 80 degrees.

  Allow to cool before using again.
• The hydration of but-2-ene?

  Catalyst= H2SO4

  Product= Butan-2-ol
• How would you measure the rate of a decomposition reaction?

  Measure the volume of gas/ mass lost at regular time intervals.
• Why does sr have a higher mp than ba?

  As sr has delocalised electrons closer to the nucleus, so stronger metallic bonding.
• What needs to stay constant when measuring the rate of reaction?

  Pressure/temp
• Explain the process that causes some molecules in this sample to have very low energies?

  Collisions causes some molecules to lose energy.
• What is the rate of reaction?

  How fast a reaction is occuring.

  Rate= change in concentration/ time.
• What is the collision theory?

  In order for particles to react, they must collide with sufficient energy.