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The Pauling electronegativity values of elements can be used to predict the chemical properties of compounds.
Use the information in Table 1.1 to answer the following questions.
Table 1.1
| element | H | Li | C | O | S |
|------------|-------|--------|-------|-------|-------|
| Pauling electronegativity value | 2.1 | 1.0 | 2.5 | 3.5 | 2.6 |
| first ionisation energy/kJ mol$^{-1}$ | 1310 | 519 | 1090 | 1310 | 1000 |
| second ionisation energy/kJ mol$^{-1}$ | — | 7300 | 2350 | 3390 | 2260 |
(a) (i) Define electronegativity.
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(ii) O and S are in Group 16.
Explain the difference in the Pauling electronegativity values of O and S.
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(b) (i) LiH is an ionic compound.
Draw a dot-and-cross diagram of LiH.
Include all electrons. [2]
(ii) Suggest the shape of a molecule of H$_2$S.
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(c) (i) Write an equation that represents the first ionisation energy of H.
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(ii) Explain why there is no information given in Table 1.1 for the second ionisation energy of H.
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(iii) Give the full electronic configuration of S$^{2+}$(g).
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(d) CO$_2$ and SO$_2$ are acidic gases.
(i) Write an equation for the reaction of SO$_2$ with H$_2$O.
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(ii) Write an equation for the reaction of SO$_2$ with NaOH.
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(iii) Construct an equation for the reaction of CO$_2$ with Mg(OH)$_2$.
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(e) (i) Complete Table 1.2 by placing a tick ($\checked$) to show which of the compounds have molecules with an overall dipole moment.
Table 1.2
| compound | O=C=O | O=S=O | S=C=S | S=C=O |
|----------|-------|-------|-------|-------|
| overall dipole moment | | | | |
[2]
(ii) At 150 °C and 103 kPa, all of the compounds listed in Table 1.2 are gases.
Under these conditions, 0.284 g of one of the compounds occupies a volume of 127 cm$^3$.
Use this information to calculate the $M_r$ of the compound. Hence, identify the compound from those given in Table 1.2.
Show your working.
$M_r =$ ........................................... identity of compound = ......................................................... [3]
[Total: 17]
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524
520
The Group 2 elements Mg to Ba are all silvery-white reactive metals.
(a) (i) Draw a labelled diagram to show the bonding and structure of the Group 2 metals at room temperature. [2]
(ii) Explain why Mg has a higher electrical conductivity than Na. [1]
(b) Write an equation for the reaction of magnesium with cold water. [1]
(c) Identify a single reagent that can be used to distinguish separate samples of dilute Mg(NO_3)_2(aq) and dilute Ba(NO_3)_2(aq).
Explain your answer.
reagent ..........................................................
explanation .................................................... [2]
(d) (i) Describe what is observed when SrI_2(aq) reacts with concentrated sulfuric acid. [2]
(ii) Compound X, an anhydrous Group 2 bromide, is dissolved in water and titrated against aqueous silver nitrate.
A solution containing 0.250 g of X requires 33.65 cm^3 of 0.0500 mol dm^{-3} AgNO_3(aq) for complete reaction.
Identify X.
Show your working.
X = ......................................................... [3]
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509
526
(a) (i) Define addition reaction.
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(ii) Aldehydes A and B are structural isomers.
State the type of structural isomerism shown by A and B.
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(iii) Name A.
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(iv) The complete reaction of propene with a 1:1 mixture of CO and H2 produces A and B only. The product mixture contains 96% A and 4% B.
Calculate the mass of A produced in this reaction when 5.00 × 103 kg of propene is used.
mass of A = .................................................. kg [1]
(b) A and B show reactions typical of aliphatic aldehydes.
(i) A undergoes a nucleophilic addition reaction with a mixture of HCN and KCN, forming compound C.
Complete the diagram to show the mechanism for this reaction.
Include charges, dipoles, lone pairs of electrons and curly arrows, as appropriate.
Draw the structure of the organic intermediate.
$$
\text{[Image of mechanism diagram]}
$$ [4]
(ii) Table 3.1 shows information about three experiments involving B.
Complete Table 3.1.
$$
\text{[Table showing experiments with columns: experiment, reagents, observation with B]}
$$ [3]
(iii) B, $C_4H_8O$, is oxidised by acidified potassium manganate(VII).
Complete the equation for this reaction. Use [O] to represent one atom of oxygen from the oxidising agent.
$C_4H_8O + ..................................................................................$ [1]
(iv) C is a chiral molecule.
Circle any chiral centres in the structure of C shown in Fig. 3.2.
$$
\text{[Image of structure]}
$$ [1]
(c) When propene reacts with CO and an excess of H2, an alkane and a mixture of alcohols are formed instead. The alcohols are isomers of each other.
Suggest the molecular formulae of the alkane and the alcohols that are formed under these conditions.
molecular formula of alkane ..................................................
molecular formula of alcohols .................................................. [2]
(d) The reaction of ethene, $C_2H_4$, with a 1:1 mixture of CO and H2 is shown in equation 1.
equation 1
$C_2H_4(g) + CO(g) + H_2(g) \rightleftharpoons CH_3CH_2CHO(g)$
At atmospheric pressure a cobalt-based catalyst is used in this reaction.
(i) State and explain the effect of using a catalyst on this reaction.
.......................................................................................................................... [2]
(ii) Explain why the yield of $CH_3CH_2CHO(g)$ increases when the overall pressure of the reaction mixture is increased.
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(iii) Use the information in Table 3.2 to calculate the enthalpy change, $\Delta H_r$, of the reaction in equation 1.
$$
\text{[Table showing enthalpy changes with columns: compound, enthalpy change of formation, }\Delta H_f^\theta \text{ kJ mol}^{-1}]
$$
$\Delta H_r = ..................................................$ kJ mol-1 [2]
(iv) The reaction mixture is cooled to collect $CH_3CH_2CHO$ as a liquid.
Identify all types of van der Waals' forces that are present between molecules of $CH_3CH_2CHO$.
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(a) (i) State the reagent and conditions used to form E in reaction 1.
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(ii) Draw the structure of one repeat unit of the addition polymer that forms from E.
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(iii) E also forms when F is heated strongly in the presence of an $Al_2O_3$ catalyst.
Write an equation for this reaction.
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(b) (i) Predict what is observed in reaction 2.
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(ii) Identify the yellow precipitate and the organic ion formed in reaction 3.
yellow precipitate ...............................................................................................
organic ion ......................................................................................................... [2]
(c) (i) State the type of reaction that occurs in reaction 4.
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(ii) Reaction 5 is similar to the reaction of $LiAlH_4$ with carboxylic acids to form alcohols.
Suggest the role of $LiAlH_4$ in reaction 5.
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(d) (i) Fig. 4.2 shows the infrared spectrum of one of the compounds D, E, F, G or H.
Use information from Table 4.1 (on page 14) to identify which of the compounds D, E, F,
G or H produces the infrared spectrum in Fig. 4.2.
Explain your answer.
.......................................................................................................................... [2]
[Table_1]
(ii) In the mass spectrum of D, the relative abundance of the molecular ion peak is 3.4.
Predict the relative abundance of the M+2 peak for D.
Explain your answer.
.......................................................................................................................... [1]
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