Rate experiments

Hydrogen peroxide decomposes according to the equation:

$2H_2O_2(aq) \rightarrow 2H_2O(l) + O_2(g)$.

In an experiment, 25.0 cm³ of aqueous hydrogen peroxide is placed in a conical flask on a balance. The initial mass is 152.0 g. After some time, oxygen gas has escaped and the mass is 151.4 g. What mass of oxygen gas has been produced?