Which of the following is NOT true about order of a reaction?

Calculate solubility $\left(\mathrm{moldm}^{-3}\right)$ of a sparingly soluble electrolyte AB at 298 K if its solubility product is $1.6 \times 10^{-5}$ ?

Which from following alkyl substituted alkenes is most stable?

In an ionic solid equal number of cations and anions are missing from their regular positions in the crystal lattice creating vacancies is called-