Helium mixed with oxygen is used in the treatment of

The kinetic energy needed to project a body of mass $m$ from the earth's surface (radius $R$) to infinity is

When bauxite powder is mixed with coke and heated with nitrogen at $2075 \ K$,carbon monoxide and $X$ are formed. Which of the following gases is produced when $X$ reacts with water?

$A$ transformer works on the principle of

In which of the following processes is $CO_2$ not produced?

The reagent used in the preparation of aspirin from salicylic acid is