A non-metal $X$ is an important constituent of our food. It forms two oxides $Y$ and $Z.Y$ is toxic and causes suffocation and even death while  $Z$ is responsible for global warming. Identify $X,Y$ and $Z$.

A brief information about a few elements is given below:

$P$: It is used in making electrodes.

$Q$: It is required for combustion.

$R$: It is used to preserve food.

$S$: It is used as fungicide.

$P,Q,R$ and $S$ are respectively.

In which of the following beakers reaction will take place?

Which of the following statements about the given reaction is/are incorrect?

${\mathrm{Fe}}_2{\mathrm{O}}_3+2\mathrm{Al}\stackrel{\mathrm{Ignited}}{\to }2{\mathrm{Fe}}_2+{\mathrm{Al}}_2{\mathrm{O}}_3$

The mixture of ${\mathrm{Fe}}_2{\mathrm{O}}_3$ and Al is ignited by inserting a magnesium ribbon and then burning it.

II. The reaction is used for welding the broken parts of iron machinery, railway tracks, etc.

III. The whole process is called aluminothermy.

IV. The reaction is highly endothermic.

Which of the following elements are metals?

(i) ${}_{12}{}^{24}P$

(ii) ${}_9{}^{18}P$

(iii) ${}_{15}{}^{31}R$

(iv) ${}_{11}{}^{23}P$

Ritika took four metals $\mathrm{P},\mathrm{Q},\mathrm{R} \mathrm{and} \mathrm{S}$ and added them to the following solutions one by one. The results are summarised in the given table.

1. Among the given metals, $Q$ is the most reactive metal. Which of the following statements are correct?
2. $\mathrm{S}$ is less reactive than $\mathrm{Zn}$ but more reactive than $\mathrm{Ag}$.
3. $\mathrm{R}$ is less reactive than $\mathrm{Ag}$ but more reactive than $\mathrm{Zn}$.
4. $\mathrm{P}$ is more reactive than $\mathrm{Cu}$ but less reactive than $\mathrm{Fe}$.

Observe the given figure carefully.

The residue left behind in the crucible, substance $Y$ and the substance which can replace $Y$ in the above process are respectively