The density of osmium, which is the densest metal, is 22.57 g/cm^3. what is the mass of a block of osmium that measures 1.00 cm x 4.00 cm x 2.50 cm? show your work.

The activation energy for the reaction no2(g)+co2(g)⟶no(g)+co(g) is ea = 300 kj/mol and the change in enthalpy for the reaction is δh = -100 kj/mol . what is the activation energy for the reverse reaction?