Given below are two statements : One is labelled as Assertion A and the other is labelled as Reason R :

Assertion (A) : $\mathrm{BeCl}_{2}$ and $\mathrm{MgCl}_{2}$ produce characteristic flame

Reason (R) : The excitation energy is high in $\mathrm{BeCl}_{2}$ and $\mathrm{MgCl}_{2}$

In the light of the above statements, choose the correct answer from the options given below :

Given below are two statements:

Statement I : According to Bohr's model of hydrogen atom, the angular momentum of an electron in a given stationary state is quantised.

Statement II : The concept of electron in Bohr's orbit, violates the Heisenberg uncertainty principle.

In the light of the above statements, choose the most appropriate answer from the options given below:

Which of the following statement(s) is/are correct?

(A) The $\mathrm{pH}$ of $1 \times 10^{-8}~ \mathrm{M} ~\mathrm{HCl}$ solution is 8 .

(B) The conjugate base of $\mathrm{H}_{2} \mathrm{PO}_{4}^{-}$ is $\mathrm{HPO}_{4}^{2-}$.

(C) $\mathrm{K}_{\mathrm{w}}$ increases with increase in temperature.

(D) When a solution of a weak monoprotic acid is titrated against a strong base at half neutralisation point, $\mathrm{pH}=\frac{1}{2} \mathrm{pK}_{\mathrm{a}}$

Choose the correct answer from the options given below:

Consider the following statements:

(A) NF₃ molecule has a trigonal planar structure.

(B) Bond length of $\mathrm{N}_{2}$ is shorter than $\mathrm{O}_{2}$.

(C) Isoelectronic molecules or ions have identical bond order.

(D) Dipole moment of $\mathrm{H}_{2}\mathrm{S}$ is higher than that of water molecule.

Choose the correct answer from the options given below: