The Covalent Model (DP IB Chemistry: HL): Exam Questions

Phosphine, PH₃, can react with a hydrogen ion, H⁺, to form the phosphonium ion.

Which type of bond is formed in this reaction?

What is the correct number of sigma (σ) and pi (π) bonds in ethanoic anhydride, CH₃COOCOCH₃?

Which of the following statements about 2-methylpropan-2-ol, CH₃C(CH₃)(OH)CH₃, are correct ? 

I.The structure contains 16 bonding pair of electrons

II.The O-C-C bond angle is 109.5 ^o

III. The total number of electrons is 32

Which of the following molecules has the biggest overall dipole?

Which of the following molecules is the most polar?

The correct order of increasing boiling points for the following compounds is

What is the strongest type of intermolecular force between serine molecules?

Hexane, C₆H₁₄ and 2,2-dimethylbutane, CH₃C(CH₃)₂CH₂CH₃, are two isomers of one another and have the same M_r of 86.0. 

Hexane has a higher boiling point than 2,2-dimethylbutane. 

Which of the following statements is not correct?

Which of the following statements about propanal and propanone are correct?

I. Both compounds exhibit dipole–dipole forces between their molecules.

II. Both compounds can form hydrogen bonds with water.

III. Propanone has a higher boiling point than propanal.

Which molecule has the lowest boiling point?

Which of the following statements about ammonia, NH₃, is not correct?

The following equation shows the dissociation equilibrium of PCl₅. 

PCl₅ (g) ⇌ PCl₃ (g) + Cl₂ (g) 

The percentage yield of PCl₃ is 13% at 160°C and increases to 97% at 300°C. 

Which of the following rows is correct?

Boron trifluoride, BF₃, reacts with trimethylamine, (CH₃)₃N, to form a compound of formula (CH₃)₃N.BF₃. 

Which diagram correctly represents this reaction using 3D structures to show the shapes of the reactants and the product?

Which of the following statements about graphite are correct? 

I.   The carbon atoms are joined together by three covalent bonds

II.   Graphite contains delocalised electrons

III.   The C-C-C bond angle is 109.5^o

Which statement about diamond and silicon is correct?

How many lone pairs of electrons are there around the chlorine atom in a molecule of chlorine trifluoride, ClF₃?

Which one of these species has a bond angle of 120°?

Which of the following statements about silicon dioxide is correct? 

I.   Silicon dioxide forms a giant covalent network

II.  Each silicon atom is covalently bonded to four oxygen atoms

III.  Silicon dioxide molecules are V-shaped

Ibuprofen is an anti-inflammatory drug that is used for treating pain, fever and inflammation. The structure is shown below.

  What are the correct bond angles for a and b?

In which molecule do all atoms, other than hydrogen, have a complete octet?

Which row in the table is correct?

Dichlorodifluoromethane, CCl₂F₂, has been used in aerosol propellants and as a refrigerant.

Which statement helps to explain why dichlorodifluoromethane is chemically inert?

Which of the following statements are true for XeO₃?

I. Has a trigonal pyramidal shape

II. One possible Lewis structure has two oxygen atoms with a formal charge of -1

III. Xenon has a formal charge of +2 in one possible Lewis structure

Which species breaks the octet rule?

Which molecule is trigonal bipyramidal in shape?

How many sigma (σ) and pi (π) bonds are present in a molecule of but-2-enoic acid?

Which combination correctly describes the geometry of BrF₄^- ?

Which species contain delocalised electrons?

I. Sulfate ion:

II. Ethanal:

III. Ozone:

Which combination describes the PH₄⁺ ion?

What is the hybridisation of the carbon and oxygen atoms in methanal, shown below?

Which species have delocalised π electrons? 

I.   CH₃COCH₃

II.  NO₂^-

III.  CO₃^2-

 The electronegativity of four elements are given below 

N = 3.0       H = 2.1       F = 4.0      P = 2.1      

What is the correct order of increasing molecular polarity (net dipole moment) for the following compounds?

What are the main types of intermolecular forces that exist between molecules of trichloromethane, CHCl₃, and between molecules of bromine, Br₂?

What is the correct structure of the chlorite ion, ClO₂^- ?

Which of the following statements about 2-chloropropene, CH₂C(Cl)CH₃ is correct?

Which of the following species have a central atom that does not have a complete octet?

I.BeCl₂

II.BF₃

IICCl₄

Which is the shortest bond length in the following gases?

Which statement best describes the intramolecular bonding in a carbonate ion, CO₃^2-?

The number of electrons in the valence shell of elements X and Y are 5 and 7 respectively.

What is the formula and type of compound formed from these elements?

The nitrate(V) ion, NO₃^-, is a polyatomic ion, bonded by covalent bonds.

Which of the following shows the correct displayed formula for the nitrate ion?

In which series of compounds does covalent character increase when going from left to right?

Which of the following molecules will have the highest boiling point?

What is the correct order of boiling points for the following molecules, from lowest to highest?

In which of the following processes do hydrogen bonds get broken?

Hydrogen bonding occurs between molecules of propanal, CH₃CH₂CHO, and molecules of liquid Y.

Which of the following is most likely to be liquid Y?

The following statements are all correct. Which of the statements can be explained, in part, by hydrogen bonding?

I.Ice is less dense than water

II.Butanone has a lower boiling point than butan-1-ol

III. At room temperature butanone can mix with water

Hydrogen bonding can occur between propanal, CH₃CH₂CHO and which other molecule?

Which of the following about dimethylamine, NH(CH₃)₂ , is correct?

Which of the following statements are correct? 

I.The strongest type of intermolecular force between BF₃ molecules are dipole-dipole forces

II.The strongest type of intermolecular force between HCN molecules are dipole-dipole forces

III. The bond angle in HCN is larger than the bond angle in BF₃

Which of the species shown below does not have resonance structures?

The correct molecular geometry and domain geometry for phosphorus trichloride, PCl₃, is:

Which row correctly describes the structure and bonding in silicon dioxide?

Which compounds have an ionic lattice structure in the solid state?

I. silicon dioxide

II. sodium iodide

III.  ammonium sulfate

What is the correct shape of a ClF₂^- ion?

Which of the following is correct for the molecules of BeCl₂ and BeCl₄^2-?

Tramadol is an example of a painkiller which is classed as an opioid analgesic. It binds to opioid receptors in the central nervous system and inhibits noradrenaline and serotonin reuptake inhibiting pain transmission.

The structure of tramadol is shown below.

Which of the following are the correct bond angles for a, b and c?

A substance has a very high melting point, excellent electrical conductivity, and contains strong covalent bonds within a single layer of atoms.

Which substance is most likely to match these properties?

Nitrous acid is produced when nitrogen dioxide dissolves in water to produce acid rain.

What is the correct Lewis structure for nitrous acid?

What is the correct number of sigma (σ) bonds and pi (π) electrons in benzoic acid?

The diagram below shows the shape of sulfur tetrafluoride, SF₄.

Which row correctly describes the bond angles in sulfur tetrafluoride, SF₄?

Which of the following species is polar?

What are the formal charges on the atoms labelled 1, 2 and 3 on the hydrogen phosphate ion, HPO₄^2-?

What are the number of sp³ hybridised atoms and sp² hybridised atoms in a molecule of cytosine?

Which species can be represented with only one Lewis structure?

In which group do both compounds contain delocalised electrons?

Which statement about sp³ hybridised carbons is not correct?

The structure of the painkiller paracetamol, often known as acetaminophen, is shown below:

Which of the following is not present in the structure?

The structure of benzene is often shown as:

This is a representation of a resonance hybrid structure that lies between these two possible structures:

Which statements provide valid evidence for this delocalised structure?

I. The carbon-carbon bond lengths are all identical and intermediate between a C-C single and C=C double bond.

II. Benzene primarily undergoes substitution reactions rather than the addition reactions typical of alkenes.

III.  The enthalpy of hydrogenation of benzene is less exothermic than expected.

Which row of the table is correct about the trend and explanation in the boiling points of the alcohols CH₃OH, C₂H₅OH and C₃H₇OH?