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14 Which phrase describes a molecule of CH4, in terms of molecular polarity and distribution of charge?(1) polar with an asymmetrical distribution of charge

(2) polar with a symmetrical distribution of charge

(3) nonpolar with an asymmetrical distribl1tion of charge

(4) nonpolar with a symmetrical distribution of charge

Verified Answer :

Edufirst

Answer: option (4) non polar with symmetrical distribuition of charge.


Justification:


1) First you have to study the presence of dipoles.


The dipoles are polar bonds with separation of positive and negative charges.


The dipoles are formed when two different atoms each with different electronegativity form a polar bond.


In this case the chemical bonds are between C and H, i.e. C - H.


The elecronegativity of C is 2.55 and the electronegativity of H is 2.20, then the difference is 2.55 - 2.20 = 2.30. This is a small difference so the C - H bonds is generally considered non polar.


2) Now look at the geometry of the molecule.


The four C atom is at the center and the four C - H bonds around the C atom form a  molecule completely symmetrical, and any charge would distributed symmetrically.

The correct phrase describing a molecule of \(\text{CH}_4\) in terms of molecular polarity and distribution of charge is \(\boxed{\left( 4 \right){\text{ nonpolar with a symmetrical distribution of charge}}}\).

Further Explanation:

Electronegativity difference is the major factor in order to govern whether the bond is polar or nonpolar. In other words, it determines the polarity of any chemical bond. A molecule is called polar if there exists an electronegativity difference between the bonded atoms. A molecule is called nonpolar if it has no or very less electronegativity difference between its atoms.

Symmetry of the molecule is also useful for the determination of polarity of any bond. If the shape of the molecule is symmetrical, it has no polarity. But if asymmetry is present in the molecule, it is said to be nonpolar.

The formula to calculate the electronegativity difference between C and H in \({\text{C}}{{\text{H}}_{\text{4}}}\) molecule is as follows:

\({\left( {{{\Delta EN}}} \right)_{{\text{C - H}}}} = {\left( {{\text{EN}}} \right)_{\text{C}}} - {\left( {{\text{EN}}} \right)_{\text{H}}}\)    …… (1)                                                     

Here,

\({\left( {{{\Delta EN}}} \right)_{{\text{C - H}}}}\) is the electronegativity difference between C and H atoms.

\({\left( {{\text{EN}}} \right)_{\text{C}}}\) is the electronegativity of carbon.

\({\left( {{\text{EN}}} \right)_{\text{H}}}\) is the electronegativity of hydrogen.

The electronegativity of C is 2.5.

The electronegativity of H is 2.1.

Substitute these values in equation (1).

\(\begin{aligned}{\left({{\Delta EN}}} \right)_{{\text{C - H}}}} &= 2.5 - 2.1\\&= 0.4\\\end{aligned}\)

The electronegativity difference between C-H bonds in \({\text{C}}{{\text{H}}_{\text{4}}}\) is 0.4, which is quite low. So \({\text{C}}{{\text{H}}_{\text{4}}}\) is a nonpolar molecule.

In \({\text{C}}{{\text{H}}_{\text{4}}}\) , the position of hydrogen atoms is symmetrical with respect to that of the central carbon atom (For structure, refer to the attached image). So this molecule has a symmetrical distribution of charge.

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Answer details:

Grade: High School

Chapter: Ionic and covalent compounds

Subject: Chemistry

Keywords: nonpolar, polar, symmetry, electronegativity difference, 2.5, 2.1, 0.4, low, CH4, electronegativity of C, electronegativity of H.

View image AkshayG