Rates of reaction

• What is the first step in the practical experiment involving sodium thiosulfate?

  Use a measuring cylinder to measure sodium thiosulfate
• What should be done after adding hydrochloric acid to the conical flask?

  Swirl the solution and start a stopwatch
• How do you determine when the reaction has occurred in the experiment?

  Look for the disappearance of the black cross
• What does repeating the experiment with different concentrations of sodium thiosulfate help to determine?

  The effect of concentration on reaction rate
• What is the second method described in the practical experiment?

  Using hydrochloric acid and magnesium to produce hydrogen gas
• What is the purpose of placing an upturned measuring cylinder over the delivery tube?

  To collect the hydrogen gas produced
• How do you measure the volume of hydrogen gas produced in the experiment?

  Measure every 10 seconds until no more gas is produced
• What conclusion can be drawn from both experiments regarding concentration and reaction rate?

  Higher concentration leads to faster reaction rates
• How does increasing temperature affect the rate of reaction?

  It increases the kinetic energy of particles
• What is the effect of a catalyst on a chemical reaction?

  It speeds up the reaction without being consumed
• What does a catalyst provide to lower activation energy?

  A different reaction pathway
• What is activation energy?

  The minimum energy required for a reaction
• method 1:

  • use a measuring cylinder to put 10cm^3 of sodium thiosulfate solution in a conical flask.
  • place a conical flask on a printed black cross.
  • Add 10cm^3 hydrochloric acid into the conical flask.
  • Swirl the solution and start a stopwatch.
  • look down at the top of the flask, until the solution turns cloudy.
  • Stop the clock when we can no longer see the cross.
  • Carry out the experiment again using lower concentrations of sodium thiosulfate Solution.
  • repeat the whole experiment and calculate the mean of each concentration of sodium thiosulfate solution.
• What is the volume of hydrochloric acid used in the experiment?

  50 cm³
• What is the purpose of attaching the conical flask to a bung and delivery tube?

  To contain the gas produced during the reaction
• Where should the delivery tube be placed during the experiment?

  Into a container filled with water
• What is placed over the delivery tube to collect gas?

  An upturned measuring cylinder
• Why is the measuring cylinder filled with water?

  To allow collection of hydrogen gas produced
• What should be done after adding magnesium to the hydrochloric acid?

  Start a stopwatch
• What gas is produced during the reaction?

  Hydrogen gas
• How often should the volume of hydrogen gas be measured?

  Every 10 seconds
• When should the measurements of hydrogen gas stop?

  When no more hydrogen is given off
• What should be done to vary the experiment?

  Use different concentrations of hydrochloric acid