Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is:

Among the following, the number of underlined elements having $+5$ oxidation state are:

Nandita mixed two solutions $\mathrm{X}$ and $\mathrm{Y}$. She recorded the following observations and conclusions in her notebook.

$\mathrm{I}.$ A yellow precipitate is formed.

$\mathrm{II}.$It is a double displacement reaction.

The solutions $\mathrm{X}$ and $\mathrm{Y}$ respectively are:

$\mathrm{Mg}+\mathrm{CuO}\to \mathrm{MgO}+\mathrm{Cu}$

Which of the following statements is wrong relating to the above equation?

Which of the following are exothermic processes?

$\mathrm{I}.$Reaction of water with quick lime.

$\mathrm{II}.$Dilution of an acid.

$\mathrm{III}.$Evaporation of water.

$\mathrm{IV}.$Sublimation of camphor.

Four students $\mathrm{P}, \mathrm{Q}, \mathrm{R},$ and $\mathrm{S}$ noted the initial colour of the solution kept in beakers $\mathrm{I}, \mathrm{II}, \mathrm{III},$ and $\mathrm{IV}$. After inserting zinc rod in each solution and leaving them undisturbed for two hours, the colour of each solution was again noted in the given table.

Which student observed the colour change in all the four beakers correctly?