Which of the following species acts as reducing agent during working of hydrogen-oxygen fuel cell?

The rate constant for a first order reaction is $0.58 \mathrm{~s}^{-1}$ at 300 K and $0.026 \mathrm{~s}^{-1}$ at 290 K .

What is the energy of activation?

$$ \left(\mathrm{R}=8.314 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}\right) $$

The reaction of propane with bromine in presence of UV light predominantly forms

Which of the following pair of compounds on heating gives butanenitrile?