Which from the following defines enthalpy of a system?

Which from following salts is NOT derived from weak acid and weak base?

Which of the following is IUPAC name of hydroquinone?

Calculate the number of atoms in 0.3 gram metal if it forms bec structure $\left[\rho \times \mathrm{a}^3=3 \times 10^{-22} \mathrm{~g}\right]$