Chemical Bonding (CIE A Level Chemistry)

The following equation shows the dissociation equilibrium of PCl₅.

PCl₅ (g)  →  PCl₃ (g)  ＋ Cl₂ (g)

The percentage yield of PCl₃ differs with temperature. 

At 160°C PCl₃ yield is 13% and at 300°C yield is 100%. 

N₂ is a covalently bonded molecule that makes up 78% of gas in the air we breathe.

Which of the following is not present in an N₂ molecule?

Using your knowledge of trends in electronegativity, deduce which of the following elements has electronegativity most similar to beryllium?

Three lone pairs of electrons can be found around the central atom of which of the following ions?

Which diagrams correctly illustrate the formation of a σ bond and a π bond from the overlap of electron orbitals?

Which of the following changes of state shows only dispersion Van der Waals’ forces being overcome?

Before the 1820s scientists believed that inorganic and organic molecules were fundamentally different and could not be interchanged, the experiment by Francis Wőhler changed this theory as he was able to produce organic urea, CO(NH₂)₂ from inorganic ammonium cyanate.

What is the formula of the cyanate ion in ammonium cyanate?

“The bond ....X…. between the hydrogen and halide in HBr is ….Y…. than in Hl.”

Which pair of words does not correctly complete the sentence above.

Which of the following molecules has the biggest overall dipole?

1.00g of propanone is reacted with 5.00g of ethane-1,2-diol and the strong acid benzene sulphonic acid, C₆H₅SO₃H. The mixture is heated under reflux in an inert solvent.

Which of the following statements is not correct?

Hydrogen bonding occurs between molecules of liquid methanal, HCHO, and molecules of liquid Y. Which of the following is most likely to be liquid Y?

A student is studying conversions of different species. The two conversions below show similarities. 

PCl₅ → PCl₆⁻

C₂H₄ → C₂H₆

What similar features do these two conversions have?

Equal amounts of 1-chloroethane, 1-bromoethane and 1-iodoethane were added to separate test-tubes each containing 2.0 cm³ of aqueous silver nitrate. The test tubes were heated and a cloudy precipitate formed in each tube. 

The equation below, within which X represents a halogen atom, and R represents CH₃CH₂, describes the hydrolysis reaction occurring within the test tubes.

The rate of AgX production, as measured by the speed of precipitation formation, was in the order AgI > AgBr > AgCl.

Why is this?

Concerning their Pauling electronegativity values, which atom is more likely to form a covalent bond with fluorine?

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

How may this reaction be written in terms of the shapes of the reactants and products?

CHCl₃ and Br₂ are both liquids at room temperature due to the existence of dipoles.

What dipoles are involved within CHCl₃ and Br₂? 

Calcium Oxide, CaO₂, can be used in toothpaste as a teeth whitener. It is formed when calcium metal burns in oxygen. Which dot-and-cross diagram correctly illustrates the electron structure of the peroxide ion in CaO₂.

Bones contain a molecule called hydroxyapatite, Ca(OH)₂.3Ca₃(PO₄)₂, which functions as a strengthening agent. 

As you age, calcium ions can be lost from hydroxyapatite, causing the bones to weaken. Strontium salt tablets can be taken to strengthen bones as the strontium ions replace the calcium ions lost from hydroxyapatite

Which of these is a correct statement?