How do we balance this half-equation?

There is a single positive charge on the silver ion.

We need to add one electron to the left hand side to balance the half-equation.

This represents a reduction reaction. The silver ion is an oxidising agent because it accepts an electron.

How do we balance this half-equation?

There are two positive charges on the copper(ll) ion.

We need to add two electrons to the left hand side to balance the half-equation.

This represents a reduction reaction. The copper(ll) ion is an oxidising agent because it accepts an electron.

How do we balance this half-equation?

There are four oxygen atoms in the manganate(Vll) ion, so we add four water molecules to the right hand side.

We need to add eight hydrogen ions to the left to balance the eight hydrogen atoms that we added to the right hand side.

There are two positive charges on the right hand side.

There are a total of seven positive charges on the left hand side.

We need to add five electrons to the left hand side to balance the charges.

This represents a reduction reaction. The manganate(Vll) ion is an oxidising agent because it accepts electrons.

How do we balance this half-equation?

There are two chromium atoms in the dichromate(Vl) ion, so we add a 2 to the right hand side to balance these.

There are seven oxygen atoms in the dichromate(Vl) ion, so we add seven water molecules to the right hand side.

We need to add fourteen hydrogen ions to the left to balance the fourteen hydrogen atoms that we added to the right hand side.

There are six positive charges on the right hand side.

There are a total of twelve positive charges on the left hand side.

We need to add six electrons to the left hand side to balance the charges.

This represents a reduction reaction. The dichromate(Vl) ion is an oxidising agent because it accepts electrons.

This half-equation shows the oxidation of zinc to zinc ions.

This half-equation shows the reduction of silver ions to silver. How do we combine these two half-equations?

Both equations need an equal number of electrons, so we multiply all of the bottom half-equation by two.

When the two half-equations are combined these electrons will cancel out.

We combine both left hand sides.

We then combine both right hand sides to complete the full equation. The silver ions are acting as an oxidising agent and the zinc atoms are acting as a reducing agent.

This half-equation shows the oxidation of iron(ll) ions to iron(lll) ions.

This half-equation shows the reduction of manganate(Vll) ions to manganese(ll) ions. How do we combine these two half-equations?

Both equations need an equal number of electrons, so we multiply all of the top half-equation by five.

When the two half-equations are combined these electrons will cancel out.

We combine both left hand sides.

We then combine both right hand sides to complete the full equation. The manganate(Vll) ions are acting as an oxidising agent and the iron(ll) ions are acting as a reducing agent.

This half-equation shows the oxidation of iron(ll) ions to iron(lll) ions.

This half-equation shows the reduction of dichromate(Vl) ions to chromium(lll) ions. How do we combine these two half-equations?

Both equations need an equal number of electrons, so we multiply all of the top half-equation by six.

When the two half-equations are combined these electrons will cancel out.

We combine both left hand sides.

We then combine both right hand sides to complete the full equation. The dichromate(Vl) ions are acting as an oxidising agent and the iron(ll) ions are acting as a reducing agent.