3.12 g of oxygen is adsorbed on 1.2 g of platinum metal. The volume of oxygen adsorbed per gram of the adsorbent at 1 atm and 300 K in L is __________.

[R = 0.0821 L atm K^$$-$$1mol^$$-$$1]

The number of significant figures in 50000.020 $$\times$$ 10^$$-$$3 is _____________.

Dichromate ion is treated with base, the oxidation number of Cr in the product formed is ___________.

Number of bridging CO ligands in [Mn₂(CO)₁₀] is __________.