A zero-order reaction has a constant rate of 4.40*10-4 m/s. if after 45.0 seconds the concentration has dropped to 1.50*10-2 m, what was the initial concentration? express your answer with the appropriate units.

The zero order means that the rate does not depend on concentration. Therefore the rate is constant even if the concentration changes. For each second it goes by 4.40 x 10^-4 is consumed

what about 45 second

=45 s x (4.4 x10^-4m/s) = 0.0198m

The total initial is therefore = 0.0198 + (1.50 x10^-2) = 0.0348m