Chemistry Test - 34

Order of base nature depends on electron donation tendency. 

In compound nitrogen  is sp2 hybridized so least basic among all given compounds. the compound  is very strong nitrogenous organic base as lone pair of one nitrogen delocalize in resonance and make another nitrogen negatively charged and conjugate acid have two equivalent resonating structure.

Thus it is most basic in given compounds.

In the presence of a catalyst, the heat evolved or absorbed during the reaction remains unchanged.The enthalpy change value of the reaction will not be affected by a catalyst. A catalyst will only lower the required activation energy for the reactions. Since it will lower the activation energy for both the forward and reverse reactions to the same extent, the net change in enthalpy is zero.

Given that:

The solution is obtained by mixing 300 g of 25% solution and 400 g of 40% solution by mass.

Therefore,

Total amount of solute present in the mixture will be given by,

\(300 \times \frac{25}{100}+400 \times \frac{40}{100}\)

\(=75+160\)

\(=235 \mathrm{~g}\)

Total amount of solution \(=300+400=700 \mathrm{~g}\)

Therefore,

Mass percentage of the solute in the resulting solution\(=\frac{\text{Total amount of solute}}{\text{Total amount of solution}} \times100\)

\(=\frac{235}{700} \times100\)

\(=33.57 \%\)

Then, mass percentage of the solvent in the resulting solution will be:

\(=(100-33.57) \%\)

\(=66.43 \%\)

A high molecular weight compound formed by combining large numbers of small molecules of low molecular weight is called Polymer.

A polymer is a large molecule composed of many repeated sub units, known as monomers.Because of their broad range of properties, both synthetic and natural polymers play an essential and ubiquitous role in everyday life.

Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins, that are fundamental to biological structure and function.Polymers, both natural and synthetic, are created via the polymerisation of many monomers.

Their large molecular mass relative to small molecular compounds produces unique physical properties, including toughness, viscoelasticity and a tendency to form glasses and semicrystalline structures rather than crystals.

For exothermic reaction \(\Delta H=\) negative and if randomness increases it means \(\Delta S\) becomes positive. Thus, according to \(\Delta G=\Delta H-T \Delta S, \Delta G\) becomes negative so, the reaction is spontaneous.

Transition metal compounds are usually coloured. This is due to the electronic transition within the d-orbitals.

Transition elements (also known as transition metals) are elements that have partially filed d orbitals.

Many ionic and covalent compounds of transition elements are coloured and this colouring property is due to \(d-d\) electronic excitation. The colour of the compound is complementary to the colour absorbed.

Plastic used to preserve yogurts is replaced with a polymer called polylactic acid is an example ofgreen chemistry.

Since usage of petroleum-based plastic is harmful to the environment, a polymer called polylactic acid, made using micro-organisms to convert cornstarch into a resin, is used to preserve yogurt. The resulting polymer is used to replace rigid petroleum-based plastic used in yogurt containers and water bottles and is environment-friendly. It is an application of green chemistry.

On dilution, milli equivalent of the solute remains constant.

Intially \(\mathrm{pH}\) of \(\mathrm{HCl}=4\)

So, normality of \(\mathrm{HCl}=10^{-4} \mathrm{~N}\)

After dilution \(\mathrm{pH}\) of \(\mathrm{HCl}=5\)

So, normality of HCl will be \(=10^{-5} \mathrm{~N}\)

\(N_{1} V_{1}=N_{2} V_{2}\)

\(10^{-4} \times 10=10^{-5} \times V\)

\(V=100 \mathrm{~mL}\)

So,the amount of water to be added to this solution in order to change its pH from 4 to 5 is\(= 100 - 10 = 90\)

Thus, 90 mL of water should be added for this pH change.

As given, the temperature is increased from \(\mathrm{T}_{1}\) to \(\mathrm{T}_{2}\), then new constants become \(\mathrm{k}_{3}\) and \(\mathrm{k}_{4}\) respectively.

Rate constant increases with increase in temperature.

So, \(k_{1}<\mathrm{k}_{3}\) and \(\mathrm{k}_{2}<\mathrm{k}_{4}\)

In the hexagonal closest packed (hcp) each ion has 12 neighboring ions, therefore, it has a coordination number of 12 and contains 6 atoms per unit cell.

The centre atom in layer B of HCP structure is touched with 12 other atoms of the same cell.