The number of stereoisomers obtained by bromination of $$trans$$-2-butene is :

Among the following the least stable resonance structure is :

A positron is emitted from $$_{11}^{23}$$Na The ratio of the atomic mass and atomic number of the resulting nuclide is :

For the process $$\mathrm{H_2O}(l)$$ (1 bar, 373 K) $$\to$$ $$\mathrm{H_2O}(g)$$ (1 bar, 373 K), the correct set of thermodynamic parameters is: