Chemistry Test - 21

Electron was discovered by J.J. Thomson. Cathode rays consist of small, negatively charged particles called electrons. The electrons are located outside the nucleus of an atom. An electron is usually represented by the symbol e^-.

Characteristics of electrons are:

• It is a negatively charged particle.
• The mass of an electron is 200 times smaller than the mass of the neutron. The mass of electron is \(9.10939 \times 10^{-31} kg\) and that of neutron is \(1.67493 \times 10^{-27} kg\).
• They are basic constituents of all-atom.
• It is a constituent of cathode rays.

Total vapour pressure \(\mathrm{P}=\mathrm{P}_{\mathrm{A}}+\mathrm{P}_{\mathrm{B}}\)

\(\mathrm{P}_{\mathrm{A}}=100 \times \frac{2}{2+3}=100 \times \frac{2}{5}=40\) torr

\(\mathrm{P}_{\mathrm{B}}=80 \times \frac{3}{2+3}=80 \times \frac{3}{5}=48\) torr

\(\mathrm{P}_{\text {Total }}=\mathrm{P}_{\mathrm{A}}+\mathrm{P}_{\mathrm{B}}=40+48=88\) torr

Ionization enthalpies of transition metals are intermediate between those of s- block and p- block elements as they are placed between s- block and p- block in the periodic table.

• The s-block elements are present on one side and the p-block elements are present on the opposite side of the periodic table and involve the filling of the s- orbitals and p- orbitals respectively.
• In between these representative elements i.e., the s- block and the p- block elements lie the d- block elements also known as the transition metals because their properties lie in between the s- block and p-block elements.

Hess's law of constant heat summation is based on the first law of thermodynamics.

Hess's law of constant heat summation states that " Regardless of multiple stages, total enthalpy changes is the sum of all the changes."

Mathematically Hess law can be represented as;

\(\Delta \mathrm{H}_{\text {net }}=\sum \Delta \mathrm{H}_{\mathrm{Y}}\)

Where, \(\Delta \mathrm{H}_{\text {net }}=\) Net enthalpy change

\(\Delta \mathrm{H}_{\mathrm{r}}=\) Sum of enthalpy change of reactions

So, Enthalpy change is a state function as it depends on the final and initial stage and not the path followed by the system. So, It resembles internal energy as internal energy is also a state function.

The first law of thermodynamics states that " Some part of internal energy of the system is used to heat the system while another part is used for work done."

So, Hess's law of constant heat summation is based on the first law of thermodynamics as both suggest the conversation of energy.

CH₃ CHO will not give Cannizzaro’s reaction because it contains a-hydrogen while other three compounds have no a-hydrogen. So, they will give Cannizzaro’s reaction.

According to Werner's theory of coordination compounds, primary valency is ionisable.

According to Werner's coordination theory, there are two kinds of valency, primary and secondary. The primary valency of a central metal ion is satisfied with anions.

Vertical columns in the periodic table starting from top to bottom are called groups. There are 18 groups in the modern periodic table. The elements of same group have same number of valence electrons.

If the valence shell electronic configuration for an element is \({ns}^2 {np}^5\), this element belongs to the group of Chalcogens, wherein, '\(n\)' refers to the value of the principal quantum number which corresponds to the valence shell of an element.

The group 16 elements of the modern periodic table consist of 5 elements oxygen, sulphur, selenium, tellurium and polonium. The elements in this group are also known as the chalcogens or the ore-forming elements because many elements can be extracted from sulphide or oxide ores.

Given, \(\mathrm{N}_1=0.5 \mathrm{~N} \), \(\mathrm{~N}_2=0.1 \mathrm{~N} \), \(\mathrm{~V}_1=100 \mathrm{~cm}^3 \), \(\mathrm{~V}_2=? \)

\(\therefore 0.5 \times 100=0.1 \times \mathrm{V}_2\)

\(\mathrm{V}_2=500 \mathrm{~cm}^3\) (Total final volume)

\(\therefore\) Volume to be added

\(=500-100=400 \mathrm{~cm}^3\)

In the simple reaction, \(2 \mathrm{NO}+\mathrm{O}_2 \rightarrow 2 \mathrm{NO}_2\)

Rate \(=\mathrm{K}[\mathrm{NO}]^2\left[\mathrm{O}_2\right]\)

If the volume of the vessel is doubled, the concentration of reactant became half.

New rate \(=\mathrm{K}\left[\frac{\mathrm{NO}}{2}\right]^2\left[\frac{\mathrm{O}_2}{2}\right]=\frac{1}{8} \mathrm{~K}\left[\mathrm{NO}]^2\left[\mathrm{O}_2\right]\right.\)

So, the new rate reduces one-eighth of the initial rate.