Which one of the following is not a functional unit of an ecosystem?

$AB_{3(g)}$ dissociates as: $AB_{3(g)} \rightleftharpoons AB_{2(g)} + \frac{1}{2}B_{2(g)}$. When the initial pressure of $AB_3$ is $800 \ torr$ and the total pressure developed at equilibrium is $900 \ torr$,what percentage of $AB_{3(g)}$ is dissociated?

The correct order of increasing $s-$character (in percentage) in the hybrid orbitals of the following molecules/ions is:
$(I)$ $CO_3^{2-}$ $(II)$ $XeF_4$ $(III)$ $I_3^-$ $(IV)$ $NCl_3$ $(V)$ $BeCl_2$

In the Young's double slit experiment using a monochromatic light of wavelength $\lambda$,the path difference (in terms of an integer $n$) corresponding to any point having half the peak intensity is :-

In the reaction,the major product formed is:

The concentration of a $100 \ mL$ solution containing $X \ g$ of $Na_2CO_3$ (molecular weight $= 106$) is $Y \ M$. The values of $X$ and $Y$ are respectively.