Chemistry Test - 22

In acidic solution, it oxidises to molecular iodine.

\(2 \mathrm{KMnO}_4+10 \mathrm{KI}+8 \mathrm{H}_2 \mathrm{SO}_4 \rightarrow 6 \mathrm{~K}_2 \mathrm{SO}_4+2 \mathrm{KMnSO}_4+5 \mathrm{I}_2+8 \mathrm{H}_2 \mathrm{O}\)

While in an alkaline or neutral solution, the iodides are oxidized to iodates.

\(2 \mathrm{KMnO}_4+\mathrm{H}_2 \mathrm{O}+\mathrm{KI} \rightarrow 2 \mathrm{MnO}{ }_2+2 \mathrm{KOH}+\underset{(\text{Iodate})}{\mathrm{K}}\)

Valance factor or \(\mathrm{n}\)-factor of \(\mathrm{KI}\) is in acidic medium as iodine charges from \(-1\) (in \(\mathrm{K I}\) ) to zero (in \(\mathrm{I}_2\) ).

In the above reaction \(\mathrm{KMnO}_4\) is an oxidizing agent because it oxidized lodide ion \(\left(\mathrm{I}^{-}\right)\) to lodine molecule and potassium iodide \(\mathrm{KI}\) is an reducing agent because it reduced potassium permanganate \(\left(\mathrm{KMnO}_4\right)\) to magnesium sulphate \(\left(\mathrm{MnSO}_4\right)\).

Thus, when alkaline \(\mathrm{KMnO}_4\) is treated with \(\mathrm{KI}\), the iodide ion is oxidised to\(\mathrm{IO}_3^{-}\).

Chain-growth polymerisation may proceed through any of the above mechanism.

In the froth flotation method, ore powder is placed in a tank filled with a mixture of water and pine oil.

• Froth flotation is an important concentration process that can be used to selectively separate hydrophobic materials from hydrophilic waste gangue.
• Froth flotation is one of the most popular operational processes for mineral beneficiation.
• In ore/mineral beneficiation, froth flotation is a method by which commercially important minerals are separated from impurities and other minerals by collecting them on the surface of a froth layer.
• Flotation is the process of separation of beneficial minerals from a mixture by creating froth on which minerals separate out.
• This method of froth floatation is a method of mineral processing in which different minerals are separated selectively.
• Such ores containing multiple metals such as lead, copper, and zinc can be selectively extracted by using froth floatation.
• The minerals that do not float into the froth are called the flotation tailings or flotation tails.

A photocell employs the photoelectric effect to convert a change in the intensity of illumination into a change in photoelectric current.

In the photoelectric effect when monochromatic radiations of suitable frequency fall on the photo-sensitive plate called the cathode, the photoelectrons are emitted which get accelerated towards the anode. These electrons flow in the outer circuit resulting in the photoelectric current.

Using the incident radiations of a fixed frequency, it is found that the photoelectric current increases linearly with the intensity of incident light. Hence, a photocell employs the photoelectric effect to convert the change in the intensity of illumination into a change in photoelectric current.

III. In carbonate ion. \(C O_{3}^{2-}\) all three \(C-O\) bonds are identical due to resonance,

IV. \(P b^{2+}\) is more stable than \(P n^{4+}\) due to the inert pair effect, hence, prefers to form divalent compounds.

Oxidation number of \(N a=+1\)

Oxidation number of \(O=-2\)

Let oxidation number of \(S=x\)

\(\therefore 2(O N\) of \(N a)+4(O N\) of \(S)+6(O N\) of \(O)=0\)

\(2(+1)+4 x+6(-2)=0\)

\(+2+4 x-12=0\)

\(4 x=+12-2\)

\(x=+\frac{10}{4}\)

\(\Rightarrow x=+\frac{5}{2}\)

Berzilius proposed that a ‘vital force’ was responsible for the formation of organic compounds.

Berzelius was a Swedish scientist who in 1815 proposed that organic compounds could only be produced by some special force which must be existing in a living organism and could not be prepared in a laboratory. This force was called vital force and this theory came to be known as vital force theory.

Hydrogen is the only non-metal placed with alkali metals.

1-phenylethanone