If the bond energies of $H-H$,$Br-Br$ and $H-Br$ are $433$,$192$ and $364 \ kJ \ mol^{-1}$ respectively,$\Delta H^o$ for the reaction $H_{2(g)} + Br_{2(g)} \to 2HBr_{(g)}$ is.....$kJ$

The hydride ion $H^{-}$ is a stronger base than the hydroxide ion $OH^{-}$. If sodium hydride $(NaH)$ is dissolved in water,which of the following reactions will occur?

What is a pulmonary vein?

For a binomial variate $X$ with $n=6$, if $P(X=2)=9 P(X=4)$, then its variance is

$A$ particle is moved from $(0, 0)$ to $(a, a)$ under a force $\vec F = (3\hat i + 4\hat j)$ along two paths. Path $1$ is $OP$ and path $2$ is $OQP$. Let $W_1$ and $W_2$ be the work done by this force in these two paths respectively. Then

On what basis are the three types of lichens classified?