what is the number of transferred electrons in 2 N2H4 + N2O4 = 3 N2 + 4 H2O?

Answer 1

In N2H4, each nitrogen has an oxidation state of -2. In N2O4, each N has an oxidation state of +4. In the product N2, the oxidation state is 0. So, a total of 4 electrons are transferred.