20 mL of 0.1 M solution of compound Na₂CO₃.NaHCO₃.2H₂O is titrated against 0.05 M HCl, x mL of HCl is used when phenolphthalein is used as an indicator and y mL of HCl is used when methyl orange is the indicator in two separate titrations. Hence, (y - x) is :

Assertion: - Law of conservation of mass holds good for nuclear reaction.

Reason:- Law states that mass can be neither created nor destroyed in a chemical reaction.

$300 \mathrm{g}$ of ${\mathrm{CaCO}}_3$ is allowed to react with $294 \mathrm{g}$ of ${\mathrm{H}}_3{\mathrm{PO}}_4$. Calculate : sum of the moles of ${\mathrm{Ca}}_3{\left({\mathrm{PO}}_4\right)}_2$ formed and moles of unreacted reagent.

Molecular mass of CaCO₃ = 100 g/mol

Molecular mass of H₃PO₄ = 98 g/mol

A chemist wants to prepare diborane by the reaction

$6\mathrm{LiH}+8{\mathrm{BF}}_3⟶6{\mathrm{LiBF}}_4+{\mathrm{B}}_2{\mathrm{H}}_6$

If we start with $32.0$ moles each of $\mathrm{LiH} \& {\mathrm{BF}}_3.$ How many moles ${\mathrm{B}}_2{\mathrm{H}}_6$ can be prepared.