Solution

An aqueous solution of lead nitrate is electrolysed.

a) What are the products formed at the anode and at the cathode?
b) What happens to the pH of the solution?

In an electrolytic cell, as well as in an electrochemical cell, the strongest oxidant will react at teh cathode and the strongest reductant will react at the anode.
Looking the electrochemical series we see that the oxidants present are water and lead(II) ions. Lead(II) ions are the strongest oxidant present.
The only reductant present is water .

So at the cathode, where reduction (electron usage) occurs, the reaction that will take place is

At the anode, where oxidation occurs (electron loss), the reaction that will take place is

So at the anode oxygen gas and hydrogen ions are produced.

The pH will decrease as the number of hydrogen ions produced steadily increase.

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An aqueous solution containing magnesium nitrate and zinc nitrate is electrolysed. Use the reactivity series on the right.

a)What are the products formed at the anode and at the cathode?
b) What happens to the pH of the solution?

In an electrolytic cell, as well as in an electrochemical cell, the strongest oxidant will react at teh cathode and the strongest reductant will react at the anode.
Looking the electrochemical series we see that the oxidants present are water and magnesium(II) ions and zinc(II) ions
Te Zinc(II) ion is the strongest oxidant present.
The only reductant present is water .

So at the cathode, where reduction (electron usage) occurs, the reaction that will take place is

So at the cathode hydrogen gas and hydroxide ions are produced.

At the anode, where oxidation occurs (electron loss), the reaction that will take place is

The pH will decrease as the number of hydrogen ions produced steadily increase.

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Solution

An aqueous solution containing ammonium iodide and zinc nitrate is electrolysed. Use the reactivity series on the right.

a)What are the products formed at the anode and at the cathode?
b) What happens to the pH of the solution?

In an electrolytic cell, as well as in an electrochemical cell, the strongest oxidant will react at the cathode and the strongest reductant will react at the anode.
Looking at the electrochemical series we see that the oxidants present are water and zinc(II) ions
The Zinc(II) ion is the strongest oxidant present.
The reductants present are water and the iodide ion.

So at the cathode, where reduction (electron usage) occurs, the reaction that will take place is

At the anode, where oxidation occurs (electron loss), the reaction that will take place is

So at the anode iodine gas is produced.

The pH will decrease as the number of hydrogen ions produced steadily increase.

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