sulfur, rate of reaction

• what are the reactants?

  sodium thiosulfate solution + hydrochloric acid
• what does the sulfur make the solution go?

  cloudy (turbidity), we can use the cloudiness to see how the long reaction takes to finish
• how much sodium thiosulfate do we measure in the measuring cylinder to then put in the conical flask?

  10cm (cubed)
• what do we place the conical flask on top of?

  a printed black cross
• how much hydrochloric acid do we add into the conical flask after its been placed on the printed cross?

  10cm (cubed)
• what do we do before starting the stopwatch?

  swirl the solution
• what do we do once the stopwatch has been started?

  we look down into the top of the flask, after a certain amount of time it will get cloudy
• when do we stop the clock?

  when we no longer see the black cross
• what do we do one we have completed the disappearing cross experiment once?

  we carry out the experiment again, this time using lower concentrations of sodium thiosulfate solution
• what do we do to calculate the mean values?

  we repeat the whole experiment again and to find the mean values for each concentration of sodium thiosulfate solution. we do not include any anomalous results when calculating a mean
• when is a measurement reproducible?

  when it can be repeated by another person or using a different technique or equipment and still get the same result.
• what is the problem with the disappearing cross experiment when it comes to reproducibility?

  different people have different eyesights, this means some people can see the cross for longer than others so they may not get the same results, however since all students use the same size printed cross, this problem shouldn't be too great
• what reaction product hydrogen gas?

  magnesium + hydrochloric acid