A buffer solution contains equal concentrations of weak acid and its salt with strong base. Calculate pH of buffer solution if dissociation constant of weak acid is $1.8 \times 10^{-5}$.

If four different elements A, B, C and D having electronic configuration as $\mathrm{A}=[\mathrm{Ne}] 3 \mathrm{~s}^2 3 \mathrm{p}^4$, $B=[\mathrm{Ne}] 3 \mathrm{~s}^2 3 \mathrm{p}^5, \mathrm{C}=[\mathrm{Ar}] 3 \mathrm{~d}^{10} 4 \mathrm{~s}^2 4 \mathrm{p}^4$ and $\mathrm{D}=[\mathrm{Ar}] 3 \mathrm{~d}^{10} 4 \mathrm{~s}^2 4 \mathrm{p}^5$.

Identify the element with largest atomic radius.

What is IUPAC name of the following compound?

For the reaction $\mathrm{A}+\mathrm{B} \longrightarrow$ product, rate law equation is, rate $=k[A]^2[B]$. If rate of reaction is $0.22 \mathrm{~mol} \mathrm{~L}^{-1} \mathrm{~s}^{-1}$, calculate rate constant. ($\mathrm{[A}]=1 \mathrm{~mol} \mathrm{~L}^{-1},[\mathrm{~B}]=0.25 \mathrm{~mol} \mathrm{~L}^{-1})$