1) The charge left on the fur is equal and opposite to the charge transferred to the rod:
In fact, when the rod is rubbed with the fur, a net charge of
has been transferred to the rod, leaving it negatively charged. If we assume the fur was initially neutral, this means that we have now an excess of positive charges on the fur, and the amount of this charge must be equal (in magnitude, but with opposite sign) to the charge transferred to the rod.
2) The mass transferred to the rod is equal to the total mass of the electrons transferred to the rod.
The charge transferred to the rod is
The charge of 1 electron is
So the number of electrons transferred is
The mass of 1 electron is
, therefore the total mass transferred to the rod is
In fact, when the rod is rubbed with the fur, a net charge of
2) The mass transferred to the rod is equal to the total mass of the electrons transferred to the rod.
The charge transferred to the rod is
The charge of 1 electron is
So the number of electrons transferred is
The mass of 1 electron is