Conductance

You will need the following equipment:

• • 6 V battery

  • ammeter

  • 2 carbon electrodes

  • alligator clips

  • connecting wires

  • anhydrous NaCl (approx. 10 g)

  • anhydrous KCl (approx. 10 g)

  • metal spatula

  • stirring rod

  • deionised water

  • 250 mL beaker

  • a balance.

Conductance and concentration

Place your beaker on the balance and tare the balance.

Add 50 g of deionised water to the beaker.

Connect the electrodes to the ammeter and battery as shown in the figure above. Record the current and mass of NaCl in the water (initially 0.0 g) in the table below.

Retare the balance and add 0.250 g of NaCl to the water in the beaker. Record the exact mass of NaCl. Stir the solution until all NaCl has completely dissolved.

Replace the electrodes in the beaker as shown above and record the current.

Repeat this step, adding 0.25 g of NaCl each time until a total mass of not more than 2.0 g of NaCl has been added. For each new solution, record the current in the circuit.

Calculate the concentration (C) of the solution for each mass of dissolved NaCl using the formula, CNaCl = mNaCl/(58.44×0.05).

Using a scatter plot, graph current versus concentration of Na+ using all your data values.

Measurements of current and mass of NaCl