9701_s07_qp_2
A paper of Chemistry, 9701
Questions:
4
Year:
2007
Paper:
2
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0
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Examiner s Use Ethene, C2H4, and hydrazine, N2H4, are hydrides of elements which are adjacent in the Periodic Table. Data about ethene and hydrazine are given in the table below. C2H4 N2H4 melting point/°C –169 +2 boiling point/°C –104 +114 solubility in water insoluble high solubility in ethanol high high Ethene and hydrazine have a similar arrangement of atoms but differently shaped molecules. What is the H-C-H bond angle in ethene? Draw a ‘dot-and-cross’ diagram for hydrazine. What is the H-N-H bond angle in hydrazine? The melting and boiling points of hydrazine are much higher than those of ethene. Suggest reasons for these differences in terms of the intermolecular forces each compound possesses. For Examiner’s Use Explain, with the aid of a diagram showing lone pairs of electrons and dipoles, why hydrazine is very soluble in ethanol. Ethene and hydrazine each react with HCl. When ethene is reacted with HCl, C2H5Cl is the only product. Using structural formulae, give an equation for the reaction between ethene and HCl. What type of reaction occurs between HCl and ethene? Explain why there is no further reaction between C2H5Cl and HCl. When aqueous hydrazine is reacted with HCl, a solid compound of formula N2H5Cl may be isolated. When an excess of HCl is used, a second solid, N2H6Cl2, is formed. Suggest what type of reaction occurs between hydrazine and HCl. What feature of the hydrazine molecule enables this reaction to occur? Suggest why one molecule of hydrazine is able to react with one or two molecules of HCl.
11. Group 17  →  11.2. The chemical properties of the halogen elements and the hydrogen halides
3. Chemical bonding  →  3.6. Intermolecular forces, electronegativity and bond properties
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For Examiner’s Use Alcohols and esters are important organic compounds which are widely used as solvents. Esters such as ethyl ethanoate can be formed by reacting carboxylic acids with alcohols. CH3CO2H + C2H5OH CH3CO2C2H5 + H2O This reaction is an example of a dynamic equilibrium. Explain what is meant by the term dynamic equilibrium. Write the expression for the equilibrium constant for this reaction, Kc. For this equilibrium, the value of Kc is 4.0 at 298 K. A mixture containing 0.5 mol of ethanoic acid, 0.5 mol ethanol, 0.1 mol ethyl ethanoate and 0.1 mol water was set up and allowed to come to equilibrium at 298 K. The final volume of solution was V dm3. Calculate the amount, in moles, of each substance present at equilibrium. For Examiner’s Use Alcohols may be classified into primary, secondary and tertiary. Some reactions are common to all three types of alcohol. In other cases, the same reagent gives different products depending on the nature of the alcohol. In the empty squares below give the structural formula of the organic compound formed in each of the reactions indicated. If no reaction occurs, write ‘no reaction’ in the space. alcohol reagentand conditions CH3CH2CH2CH2OH CH3CH2CH(OH)CH3 (CH3)3COH red phosphorus and iodine heat under reflux concentrated H2SO4 heat Cr2O7 2–/H+ heat under reflux
7. Equilibria  →  7.1. Chemical equilibria: reversible reactions, dynamic equilibrium
16. Hydroxy compounds  →  16.1. Alcohols
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For Examiner’s Use This question is about the elements in Group II of the Periodic Table, magnesium to barium. Complete the table below to show the electronic configuration of calcium atoms and of strontium ions, Sr2+. 1s 2s 2p 3s 3p 3d 4s 4p 4d Ca Sr2+ Explain the following observations. The atomic radii of Group II elements increase down the Group. The strontium ion is smaller than the strontium atom. The first ionisation energies of the elements of Group II decrease with increasing proton number. For Examiner’s Use Samples of magnesium and calcium are placed separately in cold water and left for some time. In each case, describe what you would see and write a balanced equation for each reaction. magnesium observation equation calcium observation equation Strontium nitrate, Sr(NO3)2 undergoes thermal decomposition. State one observation you would make during this reaction. Write a balanced equation for this reaction.
10. Group 2  →  10.1. Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds
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For Examiner’s Use Commercial paint and varnish removers contain a mixture of dichloromethane, CH2Cl2, and methanol, CH3OH. What would be observed when the following reactions are carried out? In each case, give the name or formula of the reaction product which is responsible for the observation you have made. CH2Cl2 is reacted with NaOHand AgNO3and the mixture left to stand. observation product responsible CH3OH is mixed with PCl5. observation product responsible CH3OH is reacted with sodium. observation product responsible When CH2Cl2 is heated under reflux with an excess of NaOH, a compound W is formed. W has the following composition by mass: C, 40.0%; H, 6.7%; O, 53.3%. Use this information and the Data Booklet to show that the empirical formula of W is CH2O. For Examiner’s Use Compounds with the empirical formula CH2O can have the molecular formula C2H4O2. Two possible structural formulae for compounds with molecular formula C2H4O2 are HCO2CH3 and H2C=C(OH)2. In the boxes below, draw displayed formulae for three further structural isomers with the molecular formula C2H4O2. Do not attempt to draw any structures containing rings or O–O bonds. X Y Z Identify which of your compounds, X, Y, or Z, will react with the following reagents. In each case, state what you would observe. solid NaHCO3 compound observation Tollens’ reagent compound observation One of the three compounds, X, Y, or Z, shows stereoisomerism. Draw displayed, labelled structures of the stereoisomers of this compound.
13. An introduction to AS Level organic chemistry  →  13.1. Formulas, functional groups and the naming of organic compounds
2. Atoms, molecules and stoichiometry  →  2.3. Formulas
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