Company is doing BAD & office manager is quitting and dividing her tasks to the rest of us when she leaves

Once she leaves, on top of our main jobs, (mine being paralegal), I would also be doing some of the administrative side of the office work. Since it is more responsibility divided among all of us, is it improper to ask for more money? I really dont want the other jobs, but if I get more money, I will mull it over....