For a zero order reaction, $\mathrm{A} \longrightarrow$ product, concentration of A decreases from $1.2 \mathrm{~mol~dm}^{-3}$ to $0.4 \mathrm{~mol~dm}^{-3}$ in 240 second. What is rate constant of the reaction?

What is the volume of oxygen required for complete combustion of 0.25 mole of methane at S.T.P.?

What type of solution the alloy is?

Which from following is NOT a salient feature of Watson and Crick model for DNA?