Gracja Kowalska kl. 2 IB

Investigation 19



Part A

  1. Put 100 cm3 of water at about 60 ºC into a polystyrene cup by mixing boiling water from the kettle with cold water from the tap.
  2. Dry about 25 g of ice with a piece of paper towel and weight them both.
  3. Rapidly record the temperature of the water and transfer the ice to it, then record the mass of the paper towel and the water it has absorbed.
  4. Stir the water ice mixture and record the temperature of the water as soon as all the ice has just melted.

Part B

  1. Take the polystyrene cup and use measuring cylinder to put 50 cm3 of 1 M aqueous copper sulphate in it.
  2. Weigh out accurately about 5 g of powdered zinc into a weighing bottle.
  3. Stir and record the temperature of the copper sulphate at half minute intervals for 2 minutes and then add the powdered zinc.
  4. Record the temperature at half minute intervals until the temperature has been falling for ten consecutive recordings.

Part A: the heat required for a change of state

Firstly, I needed to boil the water in the kettle, so that it can be used in the experiment.

Also I weighted the ice I was going to put in the water.

m= mass of ice- mass of ice in the paper= 25g – 7.1 g = 17.9 g of ice

1 mole —  18g

X   — 17.9g

X= 0.99 moles

Than, I started the experiment.

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Later on, the graph was plotted.

Graph 1: Graph showing the course of the measurement

Using informations from the table and the extrapolations from graph, I am able to calculate the enthalpy change.

∆T= temp.max – temp.min

∆T= 59.8 – 30.5

∆T= 29.3ºC

Q= m·c·∆T        where         m- mass of solution (g)

                c- specific heat capacity of H2O (J g–1 K–1)

                ∆T- change of temperature (K)

Mass of water=100 cm3 * 1 g cm-3= 100 g

Qwater= m·c·∆T

Qwater=100g* 4.18 J g–1 K–1* 29.3 K=12247.4 J

From the first law of thermodynamics we get ...

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