Consider the following data for the given reaction

$$2 \mathrm{HI}_{(\mathrm{g})} \rightarrow \mathrm{H}_{2(\mathrm{~g})}+\mathrm{I}_{2(\mathrm{~g})}$$

The order of the reaction is _________.

Mass of methane required to produce $$22 \mathrm{~g}$$ of $$\mathrm{CO}_2$$ after complete combustion is _______ g.

(Given Molar mass in g mol-1 $$\mathrm{C}=12.0$$, $$\mathrm{H}=1.0$$, $$\mathrm{O}=16.0)$$

If three moles of an ideal gas at $$300 \mathrm{~K}$$ expand isothermally from $$30 \mathrm{~dm}^3$$ to $$45 \mathrm{~dm}^3$$ against a constant opposing pressure of $$80 \mathrm{~kPa}$$, then the amount of heat transferred is _______ J.

3-Methylhex-2-ene on reaction with $$\mathrm{HBr}$$ in presence of peroxide forms an addition product (A). The number of possible stereoisomers for '$$\mathrm{A}$$' is ________.