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?

What is the amount of energy associated with first orbit of monopositive helium ion? $\left[\mathrm{R}_{\mathrm{H}}=2.18 \times 10^{-18} \mathrm{~J}\right]$