Chemistry Test - 18

Monosaccharide cannot be hydrolyzed to simpler compounds as it is itself the simplest unit.

Disaccharides, polysaccharides and oligosaccharides can be hydrolyzed to monosaccharides.

The reaction that takes place is called Hoffman's degradation reaction. The reaction of bromine with sodium hydroxide leads to the formation of sodium hypobromite (NaOBr) which in turn transforms the primary amide into an isocyanate intermediate.

An electron-donating group activates the benzene ring towards electrophilic substitution reactions. An electron-withdrawing group deactivates the benzene ring for electrophilic substitution reaction.  

Toluene, which has an electron-donating methyl group is more reactive than benzene towards electrophilic substitution. Nitrobenzene and chlorobenzene are less reactive towards electrophilic substitution reactions than benzene as they have electron-withdrawing groups attached to them. Nitro-benzene has a higher deactivating effect than Chloro-benzene.  This is because the nitro group has an electron-withdrawing resonance effect and the Chloro group has an electron-withdrawing inductive effect.  Resonance effect is stronger than inductive effect. Therefore, the order of reactivity is 2 > 1 > 3 > 4.

Ozone \((\mathrm{O_{3}})\) is also one of the greenhouse gas.

• The contribution of \(\mathrm{O_{3}}\) to the greenhouse effect is about 8 to \(10 \%\).
• About \(75 \%\) of solar energy is absorbed by the surface of the earth, and the rest is radiated back to the atmosphere.
• This heat traps gases like \(\mathrm{CO}_{2}, \mathrm{CH}_{4}, \mathrm{CFCs}\) and \(\mathrm{H}_{2} \mathrm{O}\) present in the atmosphere and adds to the heat of the atmosphere, causing global warming.

The functional group in Product \(B\) is carboxylic group \(-C O O H .\)

The first step is allylic bromination with \(N\)-bromosuccinimide (NBS) in which \(B r\) atom is added to allylic \(C\) atom of cyclohexene to give compound \(A\).

In the next step, the reaction with \(M g\) in presence of ether gives a Grignard reagent \((R-M g X)\) which then attacks a molecule of carbon dioxide. Acid hydrolysis gives carboxylic acid.

Given, The solution contains \(10 \mathrm{~g}\) per \(d m^{3}\) urea.

And, we know that: The chemical formula of urea is \(\mathrm{CH}_{4} \mathrm{~N}_{2} \mathrm{O}\).

So, molecular mass of urea \(=12+4 \times(1)+2 \times(14)+16\)\(=60 \mathrm{~gmol}^{-1}\)

So, the molarity of urea = \(\frac{\text{mass concentration}}{\text{molar mass}}\) \(=\left(\frac{10 g / d m^{3}}{60}\right)\)

\(=\frac{1}{6} m o l / d m^{3}\) 

Let's assume the molar mass of the non-volatile solution is '\(\mathrm{m}\)'.

So, the molarity of non- volatile solute =\(\frac{\text{mass concentration}}{\text{molar mass}}\) \(=\frac{50 g / d m^{3}}{m}\)

Both solutions are isotonic with each other means concentration of both solutions are same:

Molarity of urea = Molarity of non-volatile solution

\(\frac{1}{6} \mathrm{~mol} / \mathrm{dm}^{3}=\frac{50 \mathrm{~g} / \mathrm{dm}^{3}}{\mathrm{~m}}\)

By solving the above equation we get the value of '\(m\)' as:

\(m=50 \times 6 \mathrm{~gmol}^{-1}\)

\(=300 \mathrm{~gmol}^{-1}\)

Chloroform \(CHCl _{3}\) is slowly oxidized by air in the presence of light to an extremely poisonous gas, carbonyl chloride, also known as phosgene. It is therefore stored in closed dark-coloured bottles completely filled so that air is kept out.

\(2 CHCl _{3}+ O _{2} \stackrel{\text { sun light }}{\longrightarrow} 2 HCl + \underset{\text{Carbonyl Chloride}}{2COCl _{2}}(\)phosgene\()\)

\(Zn\) has the lowest enthalpy of atomisation because of the absence of any unpaired \(e ^{-} s\) in \(d\) - orbital due to which interatomic electronic bond is weakest and hence enthalpy of atomisation is lowest.

The type of isomerism shown by the complex \(\left[ CoCl _{2}( en )_{2}\right]\) is geometrical isomerism. 

Geometrical isomerism is a type of stereoisomerism having the same molecular formula and the same structural formula but differ in the spatial arrangement of atoms or groups of atoms due to the restricted rotation of double bonds.

This complex shows cis-trans isomerism. In the cis form, two \(Cl\) ligands are adjacent to each other and two en ligands are adjacent to each other. In the trans form, two \(Cl\) ligands are opposite to each other and two en ligands are opposite to each other.

The temperature at which the enzyme shows maximum activity is known asOptimum temperature.

Each enzyme has a temperature range in which a maximal rate of reaction is achieved. This maximum is known as the optimum temperature of the enzyme. The optimum temperature of each enzyme is different.

Faraday's First Law of Electrolysis states that only, according to this law, the chemical deposition due to flow of current through an electrolyte is directly proportional to the quantity of electricity (coulombs) passed through it.

The reaction is,

\(A g+e^{-} \rightarrow A g\)

By Faraday's first law of electrolysis.

1F of electricity deposits \(108 {~g}\) of \({Ag}\).

Therefore, \( 54 {~g}\) of Ag will be deposited by \(\frac{1}{108} \times 54=\frac{1}{2} F\)

Now for the reaction,

\(A l^{3+}+3 e^{-} \rightarrow A l\)

3F of electricity deposits \(27 {~g}\) of \({Al}\).

Therefore, \( \frac{1}{2} F\) will deposit \(=\frac{27}{3} \times \frac{1}{2}\)

\(=4.5 {~g}\) of \(Al\).

\(\mathrm{Cu}^{2+}\) is more stable than \(\mathrm{Cu}^{+}\).

• Stability depends on the hydration energy (enthalpy) of the ions when they bond to the water molecules.
• The \(\mathrm{Cu}^{2+}\) ion has a greater charge density than \(\mathrm{Cu}^{+}\) ion and thus, forms much stronger bonds releasing more energy.
• The extra energy needed for the second ionization of the copper is more than compensated for by the hydration, so much, so that the \(\mathrm{Cu}^{+}\) ion loses an electron to become \(\mathrm{Cu}^{2+}\) which can then release this hydration energy.

In aqueous solution \(\mathrm{Cu}^{+}\)disproportionate to \(\mathrm{Cu}^{2+}\) and \(\mathrm{Cu}\). \(2 \mathrm{Cu}^{+}\longrightarrow\mathrm{Cu}^{2+}+\mathrm{Cu}\)

Ethyl alcohol is denatured by adding methanol and pyridine.

Denatured alcohol, also called methylated spirits or wood spirit ordenatured rectified spirit, is ethanol that has additives to make itpoisonous, bad-tasting, foul-smelling, to discourage recreationalconsumption. It is sometimes dyed so that it can be identified visually.Pyridine, Methanol or both can be added to make denatured alcoholpoisonous, and denatonium can be added to make it bitter.

Given:

Mole fraction of solute in first solution \(= 0.2\)

According to Raoult's law, the relative lowering of vapour pressure is equal to the mole fraction of solute, i.e.,

\(\frac{p^{\circ}-p}{p^{\circ}}=\frac{n}{n+N}\)

or, \(\frac{\Delta p}{p^{\circ}}=\frac{n}{n+N} \)

The decrease in vapour pressure is \(10\) mm Hg:

\(\frac{10}{p^{\circ}}=0.2\)

\(\therefore p^{\circ}=50 \mathrm{~mm}\) ....(1)

For other solution of same solvent, the decrease in vapor pressure is \(20\) mm Hg:

\(\frac{20}{p^{\circ}}=\frac{n}{n+N}\)

or, \(\frac{20}{50}=\frac{n}{n+N}\) (from (1))

\(0.4=\frac{n}{n+N}\) (mole fraction of solute)

\(\because\) Mole fraction of solvent \(+\) mole fraction of solute \(=1\)

So, mole fraction of solvent \(=1-0.4=0.6\)

Given that:

Resistance, \((k)=3.16 \Omega\)

Cell constant \(=0.367 \mathrm{~cm}^{-1}\)

We know that:

Conductance, \((C)=\frac{1}{R}\)

\(=\frac{1}{3.16 \mathrm{ohm}}\)

\(=0.0316 \mathrm{~ohm}^{-1}\)

Specific conductance, \((\mathrm{\kappa}) =\) Conductance \(\times\) cell constant

\(=0.0316 \mathrm{~ohm}^{-1} \times 0.367 \mathrm{~cm}^{-1}\)

\(=0.0116 \mathrm{~ohm}^{-1} \mathrm{cm}^{-1}\)

Therefore,

Molar conductance, \(C =0.05 {M}\)

\(=0.05 {~mol} {~L}^{-1}\)

\(=\frac{0.05 {~mol}}{1 {~L}}\)

\(=\frac{0.05 {~mol}}{10^{3} {~cm}^{3}}\)

\(=0.05 \times 10^{-3} {~mol} {~cm}^{-3}\)

Molar conductivity, \(\left(\Lambda_{m}\right)=\frac{k}{C}\)

\(=\frac{\left(0.0116 {~ohm}^{-1} {~cm}^{-1}\right)}{\left(0.05 \times 10^{-3} {~mol} {~cm}^{-3}\right)}\)

\(=232 {~ohm}^{-1} {~cm}^{2} {~mol}^{-1}\)