Chemistry Random Retrieval Y13

The hydride ion, H^-, is:

(i) a reducing agent

(ii) a nucleophile

(iii) a base

(iv) a free radical

Which types of change are involved in this sequence of changes (but not necessarily in the order listed)?

CH₃CH₂CH₂OH -> CH₃CH₂CHO -> CH₃CH₂CO₂H -> CH₃CH₂CO₂CH₂CH₃

(i) hydrolysis

(ii) esterification

(iii) acid-base

(iv) oxidation

Examples of polymers that contain the amide bond include:

(i) sugars

(ii) DNA

(iii) Terylene^TM(PET)

(iv) proteins

Step 1:

When a sample of calcium carbonate reacts with dilute hydrochloric acid, 144 cm³ of carbon dioxide form in 20 seconds at room temperature and pressure.

What is the rate of loss of hydrochloric acid in moles per second. (Volume of 1 mol gas under these conditions = 24 000 cm³)

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

Consider the following homogenius gaseous equilibrium:

ethene + steam <=> ethanol

0.180 mol of ethene as mixed with 1.03 mol of steam and the the mixture heated in the presence of a catalyst. The mixture was sealed in a vessel and allowed to reach equilibrium. At equilibrium, 0.110 mol of ethanol was present in the equilibrium mixture.

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

At a given temperature, which of these expressions have a constant value for all equilibrium mixtures of hydrogen, iodine vapour and hydrogen iodide?

(i) [H₂]/[I₂],

(ii) [HI]²/[H₂][I₂],

(iii) [I₂]/[H₂]

(iv) [H₂][I₂]/[HI]²

Which of the following can act as a bidentate ligand in the formation of complexes with metal ions?

(i) S₂O₃^2-

(ii) C₂O₄^2-

(iii) SCN^-

(iv) H₂NCH₂CH₂NH₂

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

S₂O₃^2- => S₄O₆^2- + e^-

Consider a cell constructed from the following half-cells:

Mg²⁺_(aq) + 2e^- <=> Mg_(s) E^ϴcell/V = -2.37

Ag⁺_(aq) + e^- <=> Ag_(s) E^ϴcell/V = +0.80

If the solution of Mg²⁺_(aq) was 2.00 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?

In which of these complexes is the oxidation state of the metal +3?

(i) [Fe(H₂O)₅SCN]²⁺

(ii) [CoCl₄]^2-

(iii) [Cr(H₂O)₄Cl₂]⁺

(iv) [Ag(S₂O₃)₂]^2-

Which first-row d-block element has the electron configuration

1s²2s²2p⁶3s²3p⁶4s¹3d⁵?

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

3Rb_(g)=> 3Rb_(s)

What enthalpy change is represented by the following equation?

½ Br_2(l) => Br_(g)

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

Consider the following equilibrium for the reaction that generates hydrogen for use in the Haber-Bosch Process:

CH_4(g) + H₂O_(g) CO_(g) + 3H_2(g)

100 mol of CH₄ was mixed with 100 mol of H₂O and 200 mol of H₂.The mixture was given time to reach equilibrium. At this point, 350 mol of H₂ was present in the mixture. The pressure inside the 1.20 m³ vessel was measured as 400 kPa

Calculate the value of K_c (in units: mol² dm^-6) 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

Consider the following reaction.

O_3(g) + Cl_(g) => O_2(g)+ ClO_(g)

The rate equation was found, by experiment.

rate = k [O₃] [Cl]

Which of the following statements is/are true?

(i) Doubling [O₃] has no effect on the rate of the reaction

(ii) The mechanism probably has more than one step

(iii) There is one particle involved in the slowest step

(iv) The mechanism probably has only one step

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 of these statements is true of a solution of a racemic mixture?

(i) It contains asymmetric molecules,

(ii) It is a mixture of enantiomers,

(iii) It contains equal amounts of optical isomers,

(iv) It rotates the plane of polarised light

Which of these compounds have E/Z isomers?

(i) pent-2-ene,

(ii) 2-methylpent-2-ene,

(iii) 1,2-dichloropropene,

(iv) hex-1-ene

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

Which of these changes represents a termination step of a chain reaction?

(i) CH₃^. + CH₃^. -> CH₃CH₃

(ii) CH₃^. + Br₂ -> CH₃Br + Br^.

(iii) Br^. + Br^. -> Br₂

(iv) Br^. + CH₄ -> CH₃^. + HBr

Step 10:

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

Breaking down a polypeptide into amino acids by heating with dilute hydrochloric acid is an example of:

Examples of polymers that contain the amide bond include:

(i) sugars

(ii) DNA

(iii) Terylene^TM(PET)

(iv) proteins

Which of the following molecules would you predict to be the least nucleophilic?

The compound CH₃(CH₂)₄CH=CHCH₂CH=CH(CH₂)₆CO₂H is:

(i) a fatty acid

(ii) unsaturated

(iii) called octadec-9,12-dienoic acid

(iv) obtained by the hydrolysis of animal fats