Placement test A2 Level Chemistry V01

1) Bromate(V) ions, BrO₃^-, react with bromide ions, Br^-, in aqueous acid. 

BrO₃^- + 5Br^- + 6H⁺ → 3Br₂ + 3H₂O

The rate equation for the reaction is shown. 

rate = k[BrO₃^-][Br^-][H⁺]²

What are the units of the rate constant, k, for this reaction?

2) An enthalpy cycle for lead(II) nitrate is shown. All values are in kJ mol^-1. The cycle is not to scale.

 

 

 

3) Ammonia is produced from nitrogen and hydrogen in the presence of a solid catalyst in an equilibrium reaction.

 

 

4) A buffer solution contains CH₃COOH and CH₃COONa in the ratio, 1:4. What is the pH of this buffer solution? [K_a(CH₃COOH) = 1.7 × 10^-5 mol dm^-3] 

5) How many chiral centres are in the molecule shown?

 

6) Silane spontaneously combusts in air at room temperature.

SiH₄(g) + 2O₂(g) → SiO₂(s) + 2H₂O(l)

Entropy data for this reaction are shown.

Species	SiH4(g)	O2(g)	SiO2(s)	H2O(l)
So/ J K-1 mol-1	204.5	205.0	41.8	69.9

7) A student was given 50.0 cm³ of a solution of sodium hydroxide. The pH of this solution was 12.43. The student was asked to adjust the pH to 12.00, by dilution with deionised water. The student did not have access to a pH meter. Calculate the volume of deionised water, in cm³, the student should add to the original solution.

1) An equation for the reaction of FeSO₄ with KMnO₄ is shown. 

 

 

 

	Iron	Manganese
A	II → III	VII → II
B	II → III	VII → IV
C	III → II	II → VII
D	III → II	III → IV
E	I don’t have any ideas.

2) Phenol reacts with bromine to form 2,4,6‑tribromophenol. 

C₆H₅OH + 3Br₂ → C₆H₂Br₃OH + 3HBr

[M_r values: C₆H₅OH = 94.0     Br₂ = 159.8     C₆H₂Br₃OH = 330.7     HBr = 80.9]

When 5.00 g of phenol was reacted and purified, the percentage yield of 2,4,6‑tribromophenol was 76.8%. What mass of purified 2,4,6‑tribromophenol was formed?

3) Grignard reagents are very useful for increasing the length of the carbon chain of organic compounds. What best describes the role of a Grignard reagent in increasing the length of a carbon chain?

4) Which is the diagram for the cell made up of the nickel and zinc half‑cells that gives a positive value for E^o_cell? given the information from the data booklet.

Zn²⁺(aq) + 2e^- → Zn(s)              E^o = -0.76 V

Ni²⁺(aq) + 2e^- → Ni(s)                  E^o = -0.26 V

5) Which type of data is not used as evidence for the structure or stability of the benzene ring?

6) An alternative synthesis of 2,6‑dichlorophenol starts with compound C.

 

Compound C is chlorinated and hydrolysed and then the CO₂ group is removed (decarboxylation) to form 2,6‑dichlorophenol. Other than phenol, name the functional group present in compound C.

7) The capsule containing the detergent is often made from poly(ethenol) and its derivatives. Which of the following is the poly(ethenol) structure?