Write the molecular equation for sodium nitrate and lead (ii) acetate

The answer for #3 is c but i don't know why

Calculate the h3o+ concentration in a solution of acetic acid if the concentration of molecular acetic acid present at equilibrium is 9.97x10^-3 m and k for the dissociation is 1.86x10^-5. ch3cooh(aq)+h2o(> h3o^+(aq)+ch3coo^-(aq)

What is the mass of sodium in 3 moles of sodium chloride