Which from following molecules has two lone pair of electrons in valence shell of its central atom?

Identify the product ' B ' in the following sequence of reactions. Propanone $\xrightarrow{\mathrm{B_a}(\mathrm{OH})_2} A \xrightarrow[-\mathrm{H}_2 \mathrm{O}]{\Delta} B$

What time is required for 100 g of reactant to reduce to 25 g in a first order reaction having half life 5760 year?

What is the value of standard enthalpy of formation of dihydrogen?