40. Solving a chemistry problem

4) Write the equation for the following redox reactions. Determine which substance is an oxidizing agent and a reducing agent, which substance creates an environment. Indicate the degree of oxidation of the element of the oxidizing agent and the reducing agent, determine how many electrons the reducing agent gives up and the oxidizing agent accepts. Equalize the coefficients in the reaction equations.
a) Bi HNO3 (conc.) = Bi(NO3)3
b) HJ H2SO4 (conc.) =
c) NaNO2 Na2Cr2O7 H2SO4 =