IB HL Chemistry Test: Bonding

Linear Bond

2 shared 0 unshared

180 degrees

Trigonal Planar

3 shared 0 unshared

120 degrees

Trigonal Pyramidal

3 shared 1 unshared

<109.5 degrees

Tetrahedral

4 shared 0 unshared

109.5 degrees

Bent

2 shared 1 unshared

<120 degrees

Bent (pt 2)

2 shared 2 unshared

<<109.5 degrees

Trigonal Bipyramidal

5 shared 0 unshared

90 degrees and 120 degrees

Sea Saw

4 shared 1 unshared

<90 degrees and <120 degrees

T-Shaped

3 shared and 2 unshared

<90 degrees

Octahedral

6 shared and 0 unshared

90 degrees

Square pyramidal

5 shared 1 unshared

<90 degrees

Square planar

4 shared 2 unshared

90 degrees

List the highest to lowest melting points

1) Giant Covalent

2) Metallic

3) Ionic

4) Covalent

What is Covalent bonding?

The electrostatic attraction between the nuclei of two atoms and a shared pair of electrons

What is ionic bonding?

The electrostatic attraction between positive ions and negative ions (oppositely charged ions)

What is metallic bonding?

Electrostatic attraction between delocalized valence electrons and the remaining positive metal ions (cations)

What are the correct formulas for magnesium sulfate and aluminum phosphide?

MgSO4 and AlP

Which describes ionic bonding best?

The electrostatic attraction between positive ions and negative ions

Which molecule or ion contains a coordinate (dative) bond?

a. CH4

b. CO2

c. NH4 +

d. OH -

c.

Which statement best describes the intramolecular bonding in ammonia?

a. Van der Waals' forces and hydrogen bonding

b. London Dispersion forces only

c. Hydrogen Bonding Only

d. the electrostatic attraction between nuclei and shared pairs of electrons

D.

Which statements are correct about carbon to oxygen bond lengths?

I. The C to O bonds lengths are equal in CH3COOH

II. The C to O bond length in carbon monoxide is shorter than the C to O bond length in carbon dioxide

III. The C to O bond lengths in the ethanoate ion, CH3COO -, are equal

I and III only

What is the O-N-O bond angle in the NO3- ion?

120 degrees

How many bonding pairs and non-bonding pairs of electrons are around the sulfur atom in a molecule of SCl4?

4 bonding pairs and 1 non-bonding pair

According to VSEPR theory which molecules or ion are predicted to contain a bond angle less than 109 degrees?

I. NH3

II. CCl4

III. H30 +

I and III only

Show the increasing order of oxygen to oxygen bond lengths in oxygen, ozone, and hydrogen peroxide. (oxygen = O2) (ozone = O3) (hydrogen peroxide = H2O2)

O2 < O3 < H2O2

what is the shape, number of non-bonded pairs of electrons in Lewis Structure, and type of hybridization in CH2Cl2?

0 non-bonding pairs

Tetrahedral shape

Sp3 hybridization

Which is a correct statement about the NO2- ion?

a. the N atom is sp3 hybridized

b. the ion has a linear shape

c. The N atom is sp2 hybridized

d. There are two non-bonded pairs

C.

Which contains delocalized electrons?

I. CO

II. O3

III. CH3COO -

Predict the shape and bond angle of boron trichloride, BCl3

Trigonal Planar (120 degrees)

Predict the shape and bond angle of phoshporyl chloride, POCl3

Tetrahedral (109.5)

Predict the shape and bond angle of Phosphine, PH3

Trigonal Pyramidal (<109.5)

Predict the shape and bond angle of hydrogen cyanide, HCN

Linear (180)

Explain why sulfur dioxide molecules, SO2, have a bent shape whereas carbon dioxide molecules, CO2, are linear

The sulfur atom in SO2 contains three negative charge centres arranged to give a trigonal planar shape. The two bonding negative charge centres to the oxygen atoms give the molecule its bent shape with an angle of approximately 120o. In carbon dioxide there are only two negative charge centres (both bonding) around the central carbon atom so the molecule is linear.

Explain why the H-N-H angle in ammonia is smaller than the H-N-H angle in the ammonium ion

Ammonia contains one non -bonding pair of electrons around the central nitrogen atom. This

exerts a greater repulsion than the three bonding pairs so the H-N-H bond angle will be less than 109.5. In the ammonium ion the four bonding pairs of electrons around the central nitrogen atom give the ion a regular tetrahedral shape with a bond angle of 109.5

Predict the shape of xenon tetrafluoride, XeF4

Square planar

Predict the shape of iodine tetrachloride ion, ICl4-

Square planar

Predict the shape of chlorine trifluoride, ClF3

T-shaped

Predict all the F-P-F bond angles in Phosphorus pentaflouride, PF5

90, 120, 180

Predict all the F-P-F bond angles in phosphorus hexaflouride ion, PF6-

90, 180

Explain why graphite, an allotrope of the non-metal carbon, is a good conductor of electricity whereas diamond which is also an alltrope of carbon is a very poor conductor of electricity

In diamond the four outer pairs of electrons around each carbon atom are strongly bonded to four other carbon atoms to give a giant tetrahedral shape so that all the electrons are localised and not free to move. In graphite three of the pairs of electrons are localised to form strong bonds with three other carbon atoms to give a planar layers of hexagonal rings. The other two electrons are delocalised and are free to move between the layers so making graphite a good conductor of electricity

Define the term malleable

Means that a substance can be moulded or formed into thin sheets by hammering

Explain why gold conducts electricity and is a malleable metal

Gold, like all metals conducts electricity as it contains delocalised electrons which are free to move. It is malleable as the close-packed layers of positive ions held in the crystal lattice can relatively easily slide over each other or be rearranged without deforming.

Explain why the melting points of the alkali metals decrease as the atomic number of the metal increases

The melting point of a metal depends upon the way the atoms are packed, the size of the cations and the charge carried by each cation. The alkali metals are all packed the same way and each cation carries a charge of +1. However as the atomic number increases the size of the cation also increases so the charge density of the ions is less. This means the attraction to electrons is less so less energy is required to break the attractive forces holding the crystal structure together.

State the formula of:

(a) sodium carbonate

(b) aluminum phosphate

(c) calcium hydrogen carbonate

(d) chromium (iii) hydroxide

(e) copper (i) nitrate

(f) ammonium sulfate

(g) caesium iodide

(a) Na2CO3

(b) AlPO4

(c) Ca(HCO3)2

(d) Cr(OH)2

(e) CuNO3

(f) (NH4)2SO4

(g) CsI

The formula of a oxide of iron is FeO. State the formula of (a) the nitrate and (b) the chloride of iron with the same oxidation state

(a) Fe(NO3)2

(b) FeCl2

Pentane, C5H12, has three structural isomers (compounds with the same molecular formula but a different structural formula). They are pentane, 2-methylbutane, and 2,2-Dimethylpropane. Deduce with explanation, the correct order of their increasing boiling points

2,2-Dimethylpropane < 2-methylbutane < Pentane

The more spherical the molecule is, the less surface area there is to attract another molecule of the same type

Place the following four types of attractive forces in order of increasing strength. Dipole-Dipole interactions, Hydrogen bonding, London (dispersion) forces, and ionic bonding

London Dispersion forces < Dipole-Dipole interactions < Hydrogen Bonding < Ionic Bonding

One Lewis Structure for the carbonate ion, CO3 2-, shows one double C=O bond and two single C-O bonds. Explain why the bond lengths of all the carbon to oxygen bonds in the carbonate ion are equal

Three resonance structures for the carbonate ion can be drawn. Each contains one C=O double bond form the carbon atom to different oxygen atoms so that the average bond order fro the carbon to oxygen bond is 4/3 and all the carbon to oxygen bonds are the same length and strength

Explain why graphite and diamond have very high melting points, and yet diamond is a poor electrical conductor whereas graphite is a good electrical conductor

Both diamond and graphite have giant molecular structures consisting of strong covalent bonds so

they have high melting points. In diamond all the C to C bonds are equal and all the electrons are held in

fixed positions arranged tetrahedrally around each c

arbon atom. In graphite three of the C to C bonds

are fixed in a hexagonal shape with bonds angels of 120

to give a flat layer. The layers are held together

by weak bonds consisting of delocalised electrons. These delocalised electrons are free to move

between the layers so that graphite is a good conductor of electricity.

Use the information in section 8 of the IB chemistry data booklet to explain why a carbon to chlorine bond is polar

Chlorine (3.2) is more electronegative than carbon (2.6). This means that the shared pair of bonding electrons is closer to the chlorine atom, resulting in a polar bond

Carbon dioxide is a linear molecule. It contains two carbon to oxygen double bonds at 180 degrees to each other. Explain why the C=O bonds are polar and yet the molecule is non polar

C=O bonds are polar due to the greater electronegativity of oxygen compared to the carbon. The CO2 molecule is non-polar because the resultant polarity of the two oppositely opposed dipoles from the two C=O bonds is zero

0-0.2

Nonpolar covalent

0.2-1.4

polar covalent

>1.4

ionic