Chemistry Test - 39

Bond length decrease with increase in bond order. Thus, triple bonded carbon has minimum bond length.

\(\mathrm{C-C}\) bond length \(\mathrm{=1.54~ \mathring{A}}\)

\(\mathrm{C=C}\) bond length \(\mathrm{=1.33~ \mathring{A}}\)

\(\mathrm{C \equiv C}\) bond length \(\mathrm{=1.22~ \mathring{A}}\)

So, the shortest \(\mathrm{C-C}\) bond length is present in \(\mathrm{C H \equiv C-C \equiv C H}\).

If we assume that one-sixth the mass of an atom of \({ }^{12} C\) isotope is taken as the reference, the mass of one molecule of oxygen will be the same.

We know that:

\(12 \mathrm{~g} \text { of Carbon }=6.023 \times 10^{23} \text { atoms }\)

So, \(1 g=\frac{6.023 \times 10^{23}}{12} \)

\(\therefore 6 g \text { of carbon }=6 \times \frac{6.023 \times 10^{23}}{12} \)

\(=\frac{1}{2} \times 6.023 \times 10^{23}\)

This is our new Avogadro's number according to the given conditions.

Then, 1 atomic mass unit \(=\frac{1}{N_A}\)

\(=\frac{2}{6.023 \times 10^{23}}\)

Mass of 1 mole of \(O_2=32 \times\) Avogadro's number \(\times \frac{2}{6.023 \times 10^{23}}\)

\(=32 \times \frac{6.023 \times 10^{23}}{2} \times \frac{2}{6.023 \times 10^{23}} \)

\(=32 g\)

Therefore, there is no change in the mass number of \(\mathrm{O}_2\).

VSEPR theory is not related to the chemical kinetics.

Valence shell electron pair repulsion (VSEPR) theory is a model used in chemistry to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms. The VSEPR theory is used to predict the shape of the molecules from the electron pairs that surround the central atoms of the molecule

"Copper liberates hydrogen from acids." statement is not correct.

• A more reactive element can displace a less reactive element from its salt solution.
• The metals above hydrogen in the activity series react with dilute sulphuric acid and dilute hydrochloric acid to liberate hydrogen.
• The metals below hydrogen in the activity series cannot do that.
• Copper fall below hydrogen in series. Therefore, does not liberate hydrogen from acids.

In the upper layers of atmosphere ozone is formed by action of ultraviolet rays on oxygen molecule.

In the upper layer of atmosphere, the Ultraviolet rays (UV rays) split the molecule of oxygen (O₂) into its constituent 2 atoms.

Each of the atom then combine with another oxygen (O₂) molecule which gives rise to Ozone (O₃).

According to the first law of thermodynamics,

\(\Delta \mathrm{U}=\mathrm{q}+\mathrm{W} \ldots .\) (i)

Where,

\(\Delta \mathrm{U}=\) change in internal energy for a process

\(\mathrm{q}=\) heat

\(\mathrm{W}=\) work

Given,

\(\mathrm{q}=+701 \mathrm{~J}\) (Since heat is absorbed)

\(\mathrm{W}=-394 \mathrm{~J}\) (Since work is done by the system)

Substituting the values in expression (i), we get

\(\Delta \mathrm{U}=701 \mathrm{~J}+(-394 \mathrm{~J})\)

\(\Delta \mathrm{U}=307 \mathrm{~J}\)

Hence, the change in internal energy for the given process is \(307 \mathrm{~J}\).

The hydrocarbon in which all the \(4\) valencies of carbon are fully occupied is called as alkane.

Alkanes , the saturated hydrocarbons are those in which the carbon atoms are bonded covalently to each other (fully occupied). Each carbon atom is tetrahedrally surrounded by H-atoms.

Chlorine atom in \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{Cl}\) is attached to \(\mathrm{sp}^{3}\) carbon.

The structure of \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{Cl}\) is as follows:

As from the structure, it can be seen that chlorine atom in \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{Cl}\) is attached to a carbon with \(4 \sigma\) bond. 

Thus, it is attached to the \(\mathrm{sp}^{3}\) carbon atom.

\(\mathrm{W}=\frac{\mathrm{ItE}}{96500}\)

\(\therefore \mathrm{E}=\frac{\mathrm{W} \times 96500}{\mathrm{It}}\)

\(=\frac{22.2 \times 96500}{2 \times 5 \times 3600}\)

\(=59.5\)

Equivalent mass \((E)=\frac{\text { Atomic mass }}{\text { oxidation state }}\)

\(\Rightarrow 59.5=\frac{177}{\mathrm{n}} \)

\(\Rightarrow {\mathrm{n}=\frac{177}{59.5}} \)

\( \therefore \mathrm{n}= 2.97 \approx 3\)