  The scalar isoscalar form factor of the nucleon is calculated in the limit of
a large number of colours in the framework of the chiral quark-soliton model.
The calculation is based on an approximation justified by arguments from the
instanton model of the QCD vacuum, from which the chiral quark-soliton model
was derived. The simple parameter-free result reproduces all features of the
form factor observed in previous exact calculations in that model and in chiral
perturbation theory, and well agrees with the available phenomenological
information. The Feynman-Hellmann theorem is used to study the pion mass
dependence of the nucleon mass and a good agreement with lattice QCD results is
observed.
