Which of the following does not contain any co-ordinate bond?

If the coordinate axes are the bisectors of the angles between the pair of lines $ax^2 + 2hxy + by^2 = 0$ where $h^2 > ab$ and $a \neq b$,then

The $pK_a$ of a weak acid $HA$ is $4.5$. The $pOH$ of an aqueous buffered solution of $HA$ in which $50\%$ of the $HA$ acid is ionized is

Identify the reagent used in the following reaction.
Benzoic acid $\stackrel{\text{Reagent}}{\Delta}$ Benzoyl chloride + Phosphorous oxychloride + Hydrogen chloride

Which of the following have $3C-2e^-$ bond?
$I.$ $Al_2Cl_6$
$II.$ $B_2H_6$
$III.$ $Fe_2Cl_6$
$IV.$ $Si_2H_6$

How many organisms in the list given below show autotrophic nutrition method? Lactobacillus,Nostoc,Chara,Wolffia,Nitrosomonas,Nitrobacter,Porphyra,Streptococcus,Saccharomyces,Trypanosoma.