Chemistry Test - 6

Ionisation energy increases along a period from left to right and decreases down a group. The position of given elements in the periodic table is as:

Thus, the order of increasing \(\Delta H_{t_{1}}\) is \(\mathrm{Ba}<\mathrm{Ca}<\mathrm{Se}<\mathrm{S}<\mathrm{Ar}\).

Oxygen of iron oxide is removed and added to carbon monoxide to form carbon dioxide.

The reaction takes place as follows:

\(\mathrm{Fe}_{2} \mathrm{O}_{3}(s)+3 \mathrm{CO}(\mathrm{g}) \stackrel{\Delta}{\longrightarrow} 2 \mathrm{Fe}(l)+3 \mathrm{CO}_{2}(g)\)

Carbon mono oxide : oxidation

Iron oxide : reduction

Unsaturated hydrocarbons are hydrocarbons that have double or triple covalent bonds between adjacent carbon atoms.

The term "unsaturated" means more hydrogen atoms may be added to the hydrocarbon to make it saturated (i.e. consisting of all single bonds).

The example of the unsaturated compound is alkenes and alkynes, as well as branched chains and aromatic compounds.

\(\Delta \mathrm{H}<\Delta \mathrm{E}\) only if the number of moles of products is less than the number of moles of the reactants.

If \(n_{p}

\(n_{r}=\) No. of moles of reactants , \(n_{g}=\) No. of moles of gas

Therefore, \(\Delta H<\Delta E\)

At same temperature and pressure, equal volumes of gases contain the same number ofmolecules.

Avogadro's hypothesis:

• All gases containing equal moles if substance occupy the same volume at the same temperature and pressure.
• Therefore, equal volumes of gases will have an equal number of particles that can be atoms or molecules.

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.

We check each option whether it is correct or not:

The SN¹ reaction is a two-step process, with the first being a slow ionization reaction generating a carbocation. The second is the quick nucleophilic attack by the nucleophile on the carbocation.

SN¹ reactions happen in two steps: The leaving group leaves and the substrate forms a carbocation intermediate. The nucleophile attacks the carbocation, forming the product. S_X reactions do not involve transition state intermediate.

There is no intermediate in an SN² reaction, just a transition state. A transition state has no real lifetime, it is the highest energy point in the reaction coordinate as starting materials transition into products.

Number of radial nodes \(= n -l-1\)

Where \(n =\) principal quantum number, \(l=\) azimuthal quantum number

For 3p orbital \(n =3\) and \(l =1\)

\(\therefore\) Number of radial nodes for 3p orbital \(=3-1-1=3-2=1\)

Haloarenesare much less reactive than haloalkanes towards nucleophilic substitutionreactions due to the following reasons:

1.Resonance effect:  n haloarenes the electron pair on the halogen atom isin conjugation with the π – electrons of the ring and the following resonatingstructures are possible. C-Cl bond acquires a partial double bond character dueto resonance. As a result, the bond cleavage in haloarenes is difficult than incase of haloalkanes and therefore they are less reactive towards nucleophilicsubstitution reactions.

2.The C-Cl bond length in haloalkanes is 177 pm while in haloarenes it is 169 pm.Since it is difficult to break shorter bond than a longer bond. Therefore,haloarenes are less reactive than haloalkanes towards nucleophilic substitutionreactions.