Practice Paper 2 (DP IB Chemistry: HL)

But-2-ene-1,4-dioic acid exists as both cis and trans isomers. The cis isomer is shown below

Describe the type of covalent bond between carbon and hydrogen in the molecule shown above and how it is formed.

Identify how many sigma bonds and how many pi (π) bonds are present in cis but-2-ene-1,4-dioc acid.

Draw the Lewis structures, predict the shape and deduce the bond angles for xenon tetrafluoride.

Tetrafluoroethene, C₂F₄, and tetrafluorohydrazine, N₂F₄, are fluorides of adjacent elements in the Periodic Table.

Draw the Lewis (electron dot) structures for C₂F₄ and N₂F₄ showing all valance electrons.

Predict and explain the F-C-F bond angle in tetrafluoroethene and the F-N-F bond angle in tetrafluorohydrazine.

Tetrafluorohydrazine is a polar molecule but tetrafluoroethene is not.

Explain the difference in molecular polarity.

Calcium chloride has many uses including as an agent to lower the freezing point of water. It is very effective for preventing ice formation on road surfaces and as a deicer.

The Born-Haber cycle for CaCl₂ is shown:

Using Section 8 in the Data Booklet and the following information, calculate the enthalpy change for the following conversions. 

ΔH^θ_IE2 Ca = 1145 kJ mol^-1                       

ΔH^θ_at Ca = 178 kJ mol^-1

ΔH^θ_BE Cl₂ = 242 kJ mol^-1

Using Section 18 of the Data Booklet, calculate the value for the enthalpy of formation for calcium chloride, ΔH^θ_f CaCl₂. 

Aluminium oxide reacts with magnesium to form magnesium oxide and aluminium in a displacement reaction via the following reaction.

Construct a Hess’s Law cycle for this reaction

Al₂O₃ (s) + 3Mg (s) → 3MgO (s) + 2Al (s)

Outline why no values are listed for Al (s) and Mg (s) in the table given in part (a).

Calculate the enthalpy change of reaction, ΔH_r, for the reaction in part (a).

Glycolic acid, C₂H₄O₃, is a colourless, odourless crystalline solid that is highly soluble in water and behaves as a Brønsted–Lowry acid.

The systematic IUPAC name for glycolic acid is 2-hydoxyethanoic acid.

Draw the structural formula for its conjugate base, showing all the atoms and bonds.

Write an equation for the reaction between glycolic acid, C₂H₄O₃, and limescale, CaCO₃. State and explain one observation you would make.

Write an expression for the acid dissociation constant, K_a, of monochloroacetic acid.

Calculate the pH of a 0.05 M solution of monochloric acid. 

The value of K_a for monochloroacetic acid is 1.35 x 10^-3 mol dm^-3

Using Section 2 of the Data Booklet, calculate the value of [OH^-] for the solution of monochloric acid.

A 0.680 mol sample of SO₃ is introduced into a 3.04 dm³ reaction container and allowed to reach equilibrium at temperature T.
32% of the SO₃ had decomposed. 

Calculate the value for K_c in this reaction, giving your answer to 2 significant figures. 

2 SO₃ (g) ⇌ 2 SO₂ (g) + O₂ (g)      ΔH = +196 kJ mol^-1

The size of the container for the reaction in part (a) is decreased.
State the effect if any on the equilibrium constant, K_c, and the position of equilibrium. Justify your answer.

Comment on whether the reaction in part (a) is likely to take place spontaneously at temperature T.

The formulae of four organic compounds are given in Table 1. Write the names of the compounds in the second column.

Table 1

Which of the compounds in part (a) are structural isomers of each other and what type of isomerism do they show?

Propofol is a drug used to reduce consciousness during medical procedures. The skeletal structure of propofol is given in Figure 1.

Figure 1

Valeric acid, C₅H₁₀O₂, is a straight chain carboxylic acid found in the plant Valeriana officinalis.

Define the term stereoisomers.

State the conditions needed for a compound to show cis-trans isomerism.

Draw the structural formulae for the E and Z stereoisomers of pent-2-ene.

2-bromo-1-chloropropene is a colourless, odourless liquid. 

A student drew the two stereoisomers of 2-bromo-1-chloropropene below.

State what is incorrect with their diagrams of these two stereoisomers.

Outline what chemical information can be obtained about inorganic ionic substances and complex organic molecules from X-ray crystallography studies.

Explain why X-ray crystallography is not very useful for compounds containing hydrogen.

Suggest another limitation of X-ray crystallography for organic compounds. 

An electron density map obtain from the X-ray crystallography of copper metal is shown below:

Use the diagram to estimate the radius of a copper atom. The units are nm.