strong acids?

Question

strong acids are good electrolytes whilst weak acids are observed to be weak electrolytes. explain what this means and outline two ways in which you could demonstrate this property in the lab.

Answer 1

Strong electrolytes are 100% (or close) ionised in solution. Weak electrolytes aren't. So if you set up a conductivity apparatus, with voltages, electrodes, distance between the electrodes and so on being the same, the weak electrolyte will have a much lower conductivity than the strong one.

If acids ionise, they produce H+ ions. The more they ionise, the higher the concentration of H+ ions, and the lower the pH. So pH comparisons will be effective, as well as reacting both weak and strong acids with magnesium ribbon, and watching the rate of each reaction.

Answer 2

An electrolyte is a susbtance which is ionic when dissolved or molten. A strong acid is basically one which dissociates well in water, thus forming ions. A good electrolyte will conduct electricity, undergoing a redox reaction in the process.
You could demonstrate this by comparing the electrolytic properties of a strong acid to those of a weak acid.
Easy way: Make up a solution of each acid, and use a probe to measure the conductivity of the solution. The more conducing one is the better electrolyte.
Hard way: The redox reaction that occurs upon application of a current produces products at each electrode. At the cathode, H+ ions will be reduced to hydrogen, which will bubble off as a gas. So, by measuring the rate of production of hydrogen for a given voltage (capture it, and measure the volume produced over time), you can assess the relative ease with which it is produced. The better electrolyte will produce H2 faster.