Bonding

Click to start

Question 1

Which compound contains ionic bonds?

Ethanoic acid, CH3COOH

Dichloroethane,CH2Cl2

Silicon tetrabromide,SiBr4

Magnesium chloride, MgCl2

Wrong Answer!Magnesium is a metal and chlorine is a non-metal. Typically, a metal and non-metal react to form an ionic compound.

NH3 , CH4 , H2O

Question 2When CH4 , NH3 and H2O are arranged in order of

dereasing bond angle, what is the correct order?

CH4 , NH3 , H2O NH3 , H2O , CH4

H2O , NH3 , CH4

Wrong Answer!All the molecules are based upon tetrahedral arrangement of 4 regions of high electron density. However, lone pairs cause more repulsion than bonding pairs. The oxygen in H2O is surrounded by 2 lone pairs (max repulsion), the nitrogen atom in NH3 contains 1 lone pair, but the carbon in CH4 has no lone pairs ( least repulsion)

Question 3

In which of the following is there at least one double bond?

I. O2

II.CO2

III.C2F2

I only III only

I , II and IIIII and III only

Wrong Answer!The oxygen molecule (O=O) contains 1 double bond, the carbon dioxide (O=C=O) contains 2 double bonds and thetetrafluoroethane molecule contains 1 double bond

Question 4Why is the boiling point of ethane greater than that

of neon?

The ethane molecule is polar.

Hydrogen bonds form between ethane molecules but not present in liquid neon.

A molecule of ethane has a greater mass than a neon atom.

More electrons are present in ethane than in neon.

Wrong Answer!Both ethane and neon are non-polar. Hence, the predominant intermolecular and inter-atomic forces are van der Waals’ forces whose size depends on the number of electrons present in the atoms or molecules. A greater number of electrons in the ethane molecule results in a stronger temporary dipole which makes neighbouring molecules or atoms attract each other more strongly. This means more heat is reqiured to overcome the intermolecular or inter-atomic forces in ethane molecules, resulting higher boiling point.

Question 5

What is the formula for the compound formed by strontium and nitrogen?

Sr3N2 Sr2N3

SrNSr2N

Wrong Answer!Strontium form Sr2+ and nitrogen forms N3- .Hence, the formula of strontium nitride is Sr3N2

Question 6

A solid has a melting point 14400C. It conducts heat and electricity. It does not dissolve in water or in organic solvents. The bond between the particle is most likely to be

covalent ionic

metallicdipole-dipole

Wrong Answer!Generally, metals have high melting points, contain delocalized electrons, insoluble in water and excellent conductors.

Question 7

Which is the best description of metallic bonding?

The attraction between positve and negative

ions.

The attraction between the

nuclei of positive ions and delocalized valene electrons.

The attraction between nuclei and shared electron pairs.

The attraction between protons and electrons .

Wrong Answer!D is a description of covalent bonding. A is a description of ionic bonding.

Question 8

Which compound is the most soluble in water?

ethane propane

hexan-1-olpropan-1-ol

Wrong Answer!Ethane and propane are hydrocarbons and hence unable to form hydrogen bonds with water. Propan-1-ol and hexan-1-ol are both alcohols and contan hydroxyl group –OH, capable of forming hydrogen bonds with water molecules. However, propan-1-ol is more soluble since its hydrocarbon chain is smaller, 3 C atoms compared to 6 in hexan-1-ol .

Question 9

Which is not present in C2H5OC2H5 in the liquid state?

covalent bonding van der Waals’ force

hydrogen bondingdipole-dipole attractions

Wrong Answer!All of the hydrogen atoms are attached to C atoms and hence are unable to engage in hydrogen bonding.

Question 10

The angle between the two carbon-carbon bonds in CH3CHCF2 is closest to

1800 1200

9001090

Wrong Answer!The molecule has a C=C bond. There are 3 regions of high electron density around the 2 carbon atoms. Hence, the molecule is trigonal planar and has bond angles of 1200.

Question 11The molar masses of C2H6, CH3OH and CH3F are

similar. How do their boiling points compare?

C2H6<CH3OH<CH3F CH3F<CH3OH<C2H6

C2H6<CH3F<CH3OHCH3OH<CH3F<C2H6

Wrong Answer!Ethane, C2H6 has a lower boiling point due to the presence of van der Waals forces of attraction – weakest of the 3 intermolecular forces. Fluoromethane, CH3F has an intermediate boiling point owing to the presence of dipole-dipole forces. Methanol, CH3OH has the highest boiling point owing to the presence of hydrogen bonding.

Question 12

Which of the following molecules is a triangular planar?

NCl3 C2H4

SF6C3H6

Wrong Answer!C2H4 has a trigonal planar arrangement around the 2 carbon atoms.

Question 13

Which intermolecular forces exist in dry ice, CO2(s)?

dipole-dipole interactions

covalent bonds

hydrogen bondsvan der Waals’ forces

Wrong Answer!CO2 is a non-polar molecule due to its linear shape. The 2 dipoles cancel each other out. Hence, the forces operating in the soild are van der Waals’ forces.

Question 14

In general, the strengths of the following intermolecular forces and bonds increase in the order

covalent bonds, hydrogen bonds, van der Waals forces

covalent bonds, van der Waals forces, hydrogen bonds

hydrogen bonds, covalent bonds, van der Waals forces

van der Waals forces hydrogen bonds, covalent bonds

Wrong Answer!The relative order of strength is van der Waals’ forces, hydrogen bonds, covalent bonds

Question 15

Given the following electronegativity values:

H: 2.1 N: 3.0 O: 3.5 F:4.0

which bond has the greatest polarity?

O-H in H2O N-O in NO2

N-H in NH3N-F in NF3

Wrong Answer!The largest difference in electronegativity value is from O and H atoms.

Question 16

Which one of the species has a triangular pyramidal geometry?

BCl3 NCl3

C2H3H2Se

Wrong Answer!The nitrogen atom in NCl3 is surrounded by 3 bonding pairs and 1 lone pair.

II and III only

Question 17In which of the following substances would

hydrogen bonding be expected to occur?

I. C2H6

II.CH3CH2COOH

III.CH3COCH3

II only I and III only

I, II and III

Wrong Answer!A hydrogen bond would expect to occur in CH3CH2COOH since it contains hydrogen bonded directly to oxygen. The OH group is able to engage in hydrogen bonding. In the other 2 compounds, the hydrogen is bonded to C.

Question 18

When the Lewis structure for HCOOCH3 is drawn, how many bonds and how many lone pairs of electrons are present?

5 and 5 7 and 4

7 and 58 and 4

Wrong Answer!Each oxygen atom has 2 lone pairs, so there are 8 bonds. 4 x C-H, 2 C-O, 1 X C=O

Congratulations!