In gas phase bond angle in H$$_2$$O$$_2$$ is

Solutions $$A, B, C$$ and $$D$$ are respectively 0.2 M urea, $$0.10 \mathrm{~M} \mathrm{~NaCl}, 0.05 \mathrm{~M} \mathrm{~BaCl}_2$$ and 0.05 M $$\mathrm{AlCl}_3$$. All solutions are isotonic with each other except

Which among the following carbocation is most reactive?

Which of the following metals is refined by vapour phase refining in Mond process?