Hydrogen combines with other elements by

Liquid ammonia is used for refrigeration because

$2BeCl_2 + LiAlH_4 \rightarrow X + LiCl + AlCl_3$

What do you understand by the terms: $(i)$ hydrogen economy,$(ii)$ hydrogenation,$(iii)$ syngas,$(iv)$ water-gas shift reaction,and $(v)$ fuel-cell?

Which of the following is the most abundant element in the universe?

Which of the following is a drying agent that reacts with $CO_2$ and removes water vapor?