RP3-Temp on rate (HCL, sodium thiosulfate)

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Created by
Sophie Gaved

Cards (6)

  • Equipment: Measuring cylinder, hydrochloric acid, sodium thiosulfate, printed cross, beaker, thermometer, stopwatch, kettle, water bath.
  • Set up: Place a printed out cross under a beaker with sodium thiosulfate. Measure about 1/10 th of the volume of sodium thiosulfate of hydrochloric acid. Boil a kettle and leave the water to cool in a water bath.
  • Method: Record the starting temperature and then add the hydrochloric acid. Measure the time for the cross to disappear and the final temperature. Repeat, but leave the beaker in a water bath of no more than 55 degrees for a few minutes before. Then repeat the whole experiment twice more.
  • Graph: Plot a graph of ln (1/time taken) against 1/temperature (in kelvin). The gradient is - activation energy/ R where R is 8.31 J/ K mol.
  • Analysis: Rate constant k = A e ^ (Ea/R T), and the rate constant is directly proportional to 1/t. ln k = ln (1/t) = - Ea/R x (1/T) + ln A.
  • Safety: Sulfur dioxide produced is toxic - use a lid or do the experiment in a fume cupboard; HCL is an irritant - wear a lab coat and eye protection.