Chemistry Random Retrieval Y13

When propene react with hydrogen bromide the main intermediate is:

The graph from an experiment to study the decomposition of hydrogen peroxide shows how the concentration of the hydrogen peroxide varied with time at constant temperature.

Time = 0 minutes, [H₂O₂] = 0.020 mol dm^-3

Time = 654 minutes, [H₂O₂] = 0.010 mol dm^-3

Time = 1308 minutes, [H₂O₂] = 0.005 mol dm^-3

This suggests that, under the conditions of the experiment:

(i) the reaction is zero order with respect to hydrogen peroxide

(ii) the concentration after 1962 minutes was 0.0025 mol dm^-3

(iii) the rate of reaction was constant for the first 654 seconds

(iv) the half-life of the reaction was 654 minutes

Which graph represents the disappearance of a reactant that displays first order kinetics?

Consider the following equilibrium:

2SO_2(g) + O_2(g) <=>2SO_3(g)

8.00 mol of SO₂ was mixed with 5.00 mol of O₂ and the mixture sealed in a heated vessel of volume of 1.00 dm³. The mixture was left until no further observable change in composition took place. At this point, 2.00 mol of O₂ was present in the mixture and the pressure was recorded as 200 kPa.

Calculate the value K_c (in units: mol^-1 dm³) under these conditions.

Consider the following equilibrium for the Haber-Bosch process:

3H_2(g) + N_2(g) <=>2NH_3(g)

32.0 mol of H₂ was combined with 12.0 mol of N₂ and the mixture sealed and pressurised in a vessel of volume 2.00 dm³. The mixture was left until no further observable change in composition took place. At this point, 4.00 mol of NH₃ was found to be present in the mixture The pressure was recorded as 200 000 kPa.

Calculate the value of K_p (in units: kPa^-2) under these conditions.

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?

Which first-row d-block metal has the main oxidation state +2 and forms colourless compounds?

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

I₂ + e^- => I^-

I₂ = [1] 1 [2] 2 [3] 3 [4] 4 [5] 5 [6] 6

e^- = [7] 1 [8] 2 [9] 3 [10] 4 [11] 5 [12] 6

I^- = [13] 1 [14] 2 [15] 3 [16] 4 [17] 5 [18] 6

What is the value of E^ϴcell/V observed for a cell constructed from the following half-cells. (These are the half-cells that are put together in a car battery (6 cells in series)?

PbSO_4(s) + 2e^- <=> Pb_(s) + SO₄^2-_(aq) E^ϴ/V = -0.36

PbO_2(s) + SO₄^2-_(aq)+4H_(aq) + 2e^- <=> PbSO_4(s) + 2H₂O(l) E^ϴ/V = +1.69

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:

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?

The lattice enthalpy for magnesium oxide is -3850 kJ mol^-1.

The energy needed to break up 0.1 mol MgO into gaseous ions at 298K is:

[1] -38.5 kJ mol-1

[2] -385 kJ mol^-1

[3] +385 kJ mol^-1

[4] +3850 kJ mol^-1

Consider the following equilibrium:

3Fe_(s) + 4H₂O_(g) Fe₃O_4(s)+ 4H_2(g)

40.0 g of iron wool was placed in a vessel of volume 2.00 dm³. The iron was exposed to 20.0 mol of high pressure steam and the system allowed to settle to equilibrium. At equilibrium, 0.250 mol of hydrogen was found in the vessel. The gauge on the pressure vessel read 1 000 kPa. The volume of iron wool was insignificant.

Calculate the value of K_p (no units) under these conditions.

Consider the following equilibrium for the Haber-Bosch process:

3H_2(g) + N_2(g) <=>2NH_3(g)

6.00 mol of H₂ was combined with 6.00 mol of N₂ and the mixture sealed in a heated and pressurised vessel with an iron catalyst. The mixture was left until no further observable change in composition took place. At this point, 3.00 mol of NH₃ was found to be present in the mixture.

Calculate the value of the mole fraction of NH₃ present in the mixture under these conditions.

Consider the following reaction:

2ICl_(g) + H_2(g) => HCl _(g)+ I_2(g)

The rate equation was found, by experiment:

rate = k [ICl] [H₂]

Which of the following statements is/are true?

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

(ii) There are two IClparticles involved in the rate determining step

(iii) IClparticles must be involved in involved in more than one step

(iv) The rate of production of I_2(g) doubles when both [ICl] and [H] double

What are the units of k for this reaction?

By inspection of this experimental data, what is the rate equation for this reaction?

What is the value of the rate constant, k for this reaction at this temperature?

The graph from an experiment to study the decomposition of hydrogen peroxide shows how the concentration of the hydrogen peroxide varied with time at constant temperature.

Time = 0 minutes, [H₂O₂] = 0.020 mol dm^-3

Time = 654 minutes, [H₂O₂] = 0.010 mol dm^-3

Time = 1308 minutes, [H₂O₂] = 0.005 mol dm^-3

This suggests that, under the conditions of the experiment:

(i) the reaction is zero order with respect to hydrogen peroxide

(ii) the concentration after 1962 minutes was 0.0025 mol dm^-3

(iii) the rate of reaction was constant for the first 654 seconds

(iv) the half-life of the reaction was 654 minutes

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:

This is the ¹H NMR spectrum of:

Which of these chemical species are nucleophiles with react with halogenoalkanes?

(i) cyanide ions

(ii) hydroxide ions

(iii) ammonia molecules

(iv) ammonium ions

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

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

Which of these phrases describes the tertiary structure of a protein?

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

If the paracetamol molecule shown below is hydrolysed in hot dilute hydrochloric acid, what are the main organic products?

Which of the following molecules would you predict to be the most basic?

Which of the following molecules would you predict to be the most soluble in water?

Heating methylbenzene under reflux with excess, alkaline potassium manganate(VII) which is a strong oxidising agent produces: