Chemistry Random Retrieval Y13

Which of these statements defines a free radical?

When propene react with hydrogen bromide the main intermediate is:

How many peaks would you expect to see in the ¹³C spectrym of 3-propyl aminobenzene?

This is the ¹H NMR spectrum of:

The activation energy for the reaction of sodium thiosulfate with acid is close to 50 kJ mol^-1. Mixing a measured volumes of sodium thiosulfate solution and hydrochloric acid at 30^oC produces a certain amount of sulfur in 120 seconds.

Repeating the experiment with all the conditions the same except the temperature is 40 ^oC produces the same amount of sulfur in:

K_p = 4 atm for the dissociation of N₂O₄ at 350 K when the equilibrium is described by this equation.

N₂O_4(g) <=> 2NO_2(g)

What is the value of K_p for this equilibrium:

2NO_2(g) <=> N₂O_4(g)?

Which first-row d-block metal forms a reddish oxide in the +1 state which dissolves in dilute sulfuric acid to give a blue solution and a red-brown precipitate?

Which first-row d-block element is used as the catalyst for the addition of hydrogen gas to C=C double bonds?

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

H₂O => O₂ + H⁺ + e^-

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 most resistant to reduction?

High resistance voltmeters are required for accurate values of E^ϴcell/V to be measured.

What statement best describes the reasoning behind the use of a high resistance voltmeter?

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)

When pieces of tin (Sn) are added a yellow solution of acidified ammonium vanadate(V) containing the VO₂⁺_(aq) ion and the mixture allowed to stand for a few minutes, what colour will be observed in the solution?

For which of these compounds would expect the best agreement between the values of the lattice energy derived from experimental data (with the help of the Born-Haber cycle) and the values calculated from theory on the assumption that the bonding in the crystals is purely ionic?

The standard enthalpy change when one mole of an ionic compound forms from free gaseous ions is called the:

The energy change for this process:

Br_(g) + e^- -> Br^-_(g)is called the:

The indicator thymol blue changes from yellow to blue of the pH range 8.0 to 9.6. The indicator could be used to detect accurately the end-point in a titration of roughly 0.1 mol dm^-3 solutions of:

(i) ethanoic acid with sodium hydroxide

(ii) hydrochloric acid with ammonia

(iii) hydrochloric acid with sodium hydroxide

(iv) ethanoic acid with ammonia

Consider the values of the equilibrium constant for this reversible reaction:

H_2(g) +I_2(g) <=> 2HI_(g)

Temperature: 500K, value of K_c = 160

Temperature: 1000K, value of K_c = 54.

This information shows that:

(i) HI decomposes rapidly at 500 K

(ii) Raising the temperature causes the equilibrium to shift to the left

(iii) Raising the pressure causes the equilibrium to shift to the right

(iv) The reaction is exothermic

These reactions are rapid at 298 K. Which of the reactions goes effectively to completion?

(i) I^-_(aq) + I_2(aq) <=> I₃^-_(aq) K_c = 7.1 x 10^-2 mol^-1 dm³

(ii) Cu²⁺_(aq) + 4NH_3(aq) <=> [Cu(NH₃)₄]²⁺_(aq) K_c = 1.4 x 10¹³ mol^-4dm¹²

(iii) 2H₂O_(l) <=> H₃O⁺_(aq) + OH^-_(aq) K_c = 1.0 x 10^-14 mol² dm^-6

(iv) Cu²⁺_(aq) + Zn_(s) <=> Cu_(s) + Zn²⁺_(aq) K_c = 1 x 10³⁷

Consider the following reaction:

C₄H₉Cl_(aq) + OH^-_(aq) => C₄H₉OH_(aq) + Cl^-_(aq)

The rate equation was found, by experiment:

rate = k [C₄H₉Cl]

Which of the following statements is/are true?

(i) Increasing the concentrations of all reactants speeds up the nucleophilic substitution reaction

(ii) The mechanism probably has only one step

(iii) There are two particles involved in the rate determining step

(iv) OH^- is required for the overall reaction to proceed

What are the units of k for this reaction?

In which of these reactions between pairs of reagents is the bond breaking homolytic?

(i) butan-1-ol with sodium bromide and concentrated sulfuric acid

(ii) catalytic cracking of hydrocarbons

(iii) bromine with ethene

(iv) bromine with hexane

Step 1:

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

The formation of a molecules of polythene from CH₂=CH₂ involves many thousands of:

Which of these amino acids are chiral?

(i) CH₃CHNH₂CO₂H

(ii) C₆H₅CH₂CHNH₂CO₂H

(iii) HOCH₂CHNH₂CO₂H

(iv) CH₂NH₂CO₂H

In the synthesis of ethylamine from bromoethane, the reaction is performed at a high pressure with a large excess of ammonia. The principal reason(s) for this include :

(i) increasing the rate of the reaction

(ii) to minimise the chance of diethylamine and triethylamine being produced

(iii) to push the equilibrium to the right, away from the ammonium salt towards the free amine.

(iv) to reduce the activation energy for the process

Which of the following molecules is/are examples of 2^o amines?

(i) 

(ii)

(iii) 

(iv) 

During the synthesis of an ester from a carboxylic acid and an alcohol the extent of conversion of the carboxylic acid to its ester at equilibrium increases if:

(i) the alcohol is added in excess

(ii) concentrated sulfuric acid is added

(iii) the ester distills off from the reaction mixture as it forms

(iv) an acid catalyst is added

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

The reaction of propanone with HCN in the presence of some KCN is an example of: