The first vascular plants are:

Which of the following elements is used in thermometry at high temperatures?

The mechanism of the reaction $2NO_2 + F_2 \to 2NO_2F$ is given by:
$(i)$ $NO_2 \xrightarrow{slow} NO_2^*$
$(ii)$ $NO_2^* + F_2 \xrightarrow{fast} NO_2F + F$
$(iii)$ $F + NO_2 \xrightarrow{fast} NO_2F$
Select the correct statement regarding this reaction.

Energy of an electron in the ground state of the hydrogen atom is $-2.18 \times 10^{-18} \, J$. Calculate the ionization enthalpy of atomic hydrogen in terms of $J \, mol^{-1}$.

At $298 \ K$,the value of $-\frac{\Delta[Br^-]}{\Delta t}$ for the reaction $5 Br^- (aq) + BrO_3^- (aq) + 6 H^+ (aq) \rightarrow 3 Br_2 (aq) + 3 H_2 O (l)$ is $x \ mol \ L^{-1} \ min^{-1}$. What is the rate (in $mol \ L^{-1} \ min^{-1}$) of this reaction?

In green plants,cell elongation in the internodal regions is caused by which of the following?