We know that,

Potential difference V is the work done per unit positive charge in taking a small test charge from conductor 2 to 1 against the field. Consequently, V is also proportional to Q and the ratio Q/V is a constant C known as capacitance of the capacitor.

The value of this capacitance depends only on the size, shape and position of conductor and its plates and not on the potential difference applied by the battery or th charge on the plates.

For example: the capacitance in case of an isolated spherical capacitor is given by

Where,

R=radius of the spherical conductor.

∴ Capacitance cannot be said to be dependent on charge Q.

Thus, capacitance of the capacitor is independent of the charge on the capacitor.