Chemistry Random Retrieval Y13

Reagents which can be used in a test-tube test to distinguish aldehydes from ketones are:

(i) Tollen's reagent

(ii) 2,4-dinitrophenylhydrazine

(iii) Fehling's solution

(iv) sulfuric acid

Which of the listed liquids reacts with sodium borohydride NaBH₄ in a nucleophilic addition reaction?

(i) CH₃CH₂OH

(ii)CH₃COCH₃

(iii)CH₃CO₂H

(iv)CH₃CHO

Which of these characteristics of polymers accounts for the difference between low density and high density poly(ethene)?

[1] the average length of the polymer chains

[2] the type of intermolecular (interchain) forces

[3] the number and size of bulky side groups

[4] the extent of chain branching

Step 10:

Step 8:

Which of these conversions is an example of nucleophilic substitution?

How many peaks would you expect to see in the ¹³C spectrym of 2,5-dimethyltetrahydrofuran?

Consider the synthesis of methanol in the following equilibrium:

CO_(g) + 2H_2(g) <=>CH₃OH_(g)

2.00 mol of CO was mixed with 4.00 mol of H₂ and the mixture sealed in a container. The mixture was left until no further observable change in composition took place. At this point, 1.90 mol of CH₃OH was present in the mixture.

Calculate the value of the mole fraction of CH₃OH present in the mixture under these conditions.

What is the value of E^ϴcell/V observed for a cell constructed from the following half-cells?

V³⁺_(aq) + e^- <=> V²⁺_(aq) E^ϴcell/V = -0.26

VO₂⁺_(aq) + 2H⁺_(aq) + e^- <=> VO²⁺_(aq) + H₂O_(l) E^ϴcell/V = +1.00

Consider a cell constructed from the following half-cells:

Zn²⁺_(aq) + 2e^- <=> Zn_(s) E^ϴ/V = -0.76

Cu²⁺_(aq) + 2e^- <=>Cu_(s) E^ϴ/V = +0.34

If the solution of Cu²⁺_(aq) was 0.50 mol dm^-3, would you expect to see a greater or smaller value of E^ϴcell/V than you would if the cell was set-up under standard conditions?

Consider the following 3 equilibria, all involving metallic copper or its ions:

Cu²⁺_(aq) + e^- <=> Cu⁺_(aq) E^ϴ/V = +0.15

Cu²⁺_(aq) + 2e^- <=> Cu_(s) E^ϴ/V = +0.34

Cu⁺_(aq) + e^- <=> Cu_(s) E^ϴ/V = +0.52

An aqueous solution of the colourless compound, CuCl_(s) was prepared and the solution was left to stand for a period in a sealed colourless glass bottle.

After the solution was left to stand, the contents of the bottle would have the following appearance:

For this question, look at the resource, ‘A Selection of Standard Electrode Potentials’ (‘A Selection of Standard Electrode Potentials’can be found in TOOLS>Data Sheets)

Which chemical species is reduced most easily?

What is the value of E^ϴcell/V observed for a cell constructed from the following half-cells? These half-cells are those involved in Hydrogen Fuel Cells when operated in acidic conditions?

H⁺_(aq) + e^-<=> ½H_2(g) (acidic conditions) E^ϴ/V = 0.00

O_2(g)+ 4H⁺_(aq) + 4e^-<=>2H₂O_(g) (acidic conditions) E^ϴ/V = +1.23

Work out the ratio of the species in the following half-equation.

C₂O₄^2- => CO₂ + e^-

Using oxidation numbers (states) work out the ratio of the species in the following half-equation.

S₂O₃^2- => S₄O₆^2- + e^-

From your calculation of ΔG in question 8, decide whether the reaction between high pressure steam and methane will be feasible at 1500^oC.

If this question is from a Random Retrieval, you can also carry out this calculation of Gibbs Energy change, ΔG by first working out values for ΔS^Ɵ and ΔH^Ɵ by selecting the appropriate data from the ‘Selection of Thermodynamic Data’ in TOOLS.

Calculate the value of the enthalpy change associated with the following equation?

N_2(g) + 3H_2(g) => 2NH_3(g)

Consider the following equilibrium:

PCl_3(g) + Cl_2(g) <=> PCl_5(g)

6.00 mol of PCl₃was mixed with 6.00 mol of Cl₂ and the mixture sealed in a vessel and allowed to reach equilibrium. At equilibrium, 2.00 mol of PCl₅ was present in the equilibrium mixture.

Calculate the value of the mole fraction of PCl₅ present in the mixture under these conditions.

Consider the following reaction:

NO_2(g) + CO_(g) => NO_(g)+ CO_2(g)

The rate equation was found, by experiment:

rate = k [NO₂]²

Which of the following statements is/are true?

(i) The mechanism has more than one step

(ii) CO is involved in the rate determining step

(iii) NO₂ is produced in one of the steps

(iv) The mechanism has only one step

Nitrogen monoxide gas reacts with oxygen gas to form nitrogen dioxide gas. If the rate of formation of nitrogen dioxide is 1.4 x 10^-5 mol dm^-3, what is the rate of disappearance of oxygen?

Which statement helps to explain why propene react with hydrogen bromide to form mainly 2-bromopropane and much less 1-bromopropane?

In which of these organic compounds are all the bonds non-polar?

(i) 1-bromobutane

(ii) butene

(iii) butan-2-ol

(iv) butane

Methane reacts with chlorine in the presence of ultraviolet light. The reactive chemical species which attacks methane molecules during the reaction is:

Step 2:

Step 8:

Step 10:

What is the repeat unit in the polymer formed from propene?

Which of these molecules does NOT consist of one or more chains of amino acids?

(i) The hormone insulin

(ii) The filaments in muscle fibres

(iii) The enzyme in saliva, amylase

(iv) The genetic material, DNA

What are the reagents and conditions for converting benzene to bromobenzene?

Excess LiAlH₄ in dry ether (this reacts similarly to NaBH₄ but is more reactive), converts propanoic acid to: