Olympiad/HOTS corner

In the double displacement reaction between aqueous potassium iodide and aqueous lead nitrate, a yellow precipitate of lead iodide is formed. While performing the activity if lead nitrate is not available, which of the following can be used in place of lead nitrate?

The equation $\mathrm{Mg}\left(\mathrm{s}\right)+\mathrm{CuO}\left(\mathrm{s}\right)\to \mathrm{MgO}\left(\mathrm{s}\right)+\mathrm{Cu}\left(\mathrm{s}\right)$ represents

$\mathrm{A}.$ Decomposition reaction

$\mathrm{B}.$ Displacement reaction

$\mathrm{C}.$ Combination reaction

$\mathrm{D}.$ Double displacement reaction

$\mathrm{E}.$ Redox reaction

The energy diagram shows the energy levels of reactants and products of a particular reaction.

Which of the following processes can be related to the given diagram?

The chemical reactions and their corresponding observable features are matched below. The correct option is:

A science teacher wrote the following statements about rancidity:

$\left(\mathrm{i}\right)$ When fats and oils are reduced, they become rancid.

$\left(\mathrm{ii}\right)$ In chips packet, rancidity is prevented by oxygen.

$\left(\mathrm{iii}\right)$ Rancidity is prevented by adding antioxidants.

Select the correct option.

Which on of the following is an example of a redox reaction?

Classify each of the following reactions:

$$\begin{gathered} \mathrm{Zn}\left(\mathrm{s}\right)+2{\mathrm{AgNO}}_3\left(\mathrm{aq}\right)\to \mathrm{Zn}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{aq}\right)+2\mathrm{Ag}\left(\mathrm{s}\right) \\ \mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{s}\right)\stackrel{∆}{\to }\mathrm{CaO}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{g}\right) \\ \mathrm{Cu}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{aq}\right)+2{\mathrm{Na}}_2\mathrm{S}\left(\mathrm{aq}\right)\to \mathrm{CuS}\left(\mathrm{s}\right)+2{\mathrm{NaNO}}_3\left(\mathrm{aq}\right) \\ {\mathrm{H}}_2{\mathrm{SO}}_3\left(\mathrm{aq}\right)+2\mathrm{KOH}\left(\mathrm{aq}\right)\to {\mathrm{K}}_2{\mathrm{SO}}_3\left(\mathrm{aq}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \end{gathered}$$

$\mathrm{P}, \mathrm{Q},$ and $\mathrm{R}$ are three metals that undergo chemical reactions as follows:
$$\begin{gathered} {\mathrm{P}}_2{\mathrm{O}}_3+2\mathrm{Q}\to {\mathrm{Q}}_2{\mathrm{O}}_3+2\mathrm{P} \\ 2\mathrm{P}+3\mathrm{RO}\to {\mathrm{P}}_2{\mathrm{O}}_3+3\mathrm{R} \\ 3{\mathrm{RSO}}_4+2\mathrm{Q}\to {\mathrm{Q}}_2{\left({\mathrm{SO}}_4\right)}_3+3\mathrm{R} \end{gathered}$$

Observe the reactions and arrange the metals in the increasing order of their reactivity.