9701_m19_qp_22 - revisedeck

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Nitrogen, N2, is the most abundant gas in the Earth’s atmosphere and is very unreactive. State why N2 is very unreactive. Magnesium and lithium both form nitrides with N2. These compounds both contain the N3– ion. Write an equation for the reaction of magnesium with N2 to form magnesium nitride. Solid lithium nitride, Li3N, reacts with water according to the following equation. Li3N+ 3H2O3LiOH+ NH3State one observation you would make during this reaction. State the industrial importance of ammonia. One method of producing NH3 is by heating ammonium chloride, NH4Cl, with CaO. 2NH4Cl + CaO 2NH3 + CaCl 2 + H2O Explain why the reaction of NH4Cl with CaO produces ammonia. Three oxides of nitrogen, NO, NO2 and N2O, can be formed under different conditions. Complete the table to give the oxidation numbers of nitrogen in NO and NO2. compound NO NO2 oxidation number of N NO2 can be formed by different chemical reactions. Write equations for the formation of NO2 by: ● the reaction of N2 with O2 ● the thermal decomposition of magnesium nitrate. Molecules of N2O can be formed by the reaction between N2 and O2. The bond between the N and O atoms (N O) is a co-ordinate (dative covalent) bond. 2N2+ O22N≡N OThe enthalpy change of reaction for this reaction is +82 kJ mol–1. Calculate the bond enthalpy, in kJ mol–1, of the N O bond. Use relevant data from the Data Booklet to answer this question. bond enthalpy of the N O bond = kJ mol–1 Nitrosyl chloride, NOCl, is a reactive gas that is sometimes formed when NO reacts with Cl 2. N Cl O nitrosyl chloride δ+ δ– NOCl is a strong electrophile and readily undergoes an addition reaction with alkenes. Complete the diagram to show the mechanism of the electrophilic addition reaction of NOCl with ethene. Include all necessary charges, lone pairs and curly arrows, and the structure of the organic intermediate. N Cl O C H H H H C δ+ δ– C H N O C H H Cl H

12. Nitrogen and sulfur → 12.1. Nitrogen and sulfur

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The elements in Group17 of the Periodic Table are called the halogens. They form stable compounds with both metals and non-metals. The table gives some data about F2, HCl and CaF2. F2 HCl CaF2 boiling point / K relative formula mass 38.0 36.5 78.1 State what is meant by the term relative formula mass. F2 and HCl are both covalent molecules. Suggest why the boiling point of HCl is higher than that of F2. Explain why CaF2 has a very high boiling point. CaF2can be made by the reaction of calcium carbonate with hydrofluoric acid, HF. Write an equation for this reaction. Include state symbols. Complete the electronic configuration of a chloride ion. 1s2 When Cl 2 is passed over hot iron, FeCl 3 is formed. However, when I2is passed over hot iron, the following reaction occurs. Fe+ I2FeI2State what you would observe during the reaction between Fe and I2. Explain why FeI2is formed rather than FeI3. observation explanation FeI2 is soluble in water. A student carries out a chemical test to confirm that a solution of FeI2 contains aqueous iodide ions, I–. The student adds a single reagent and a precipitate forms. Identify the reagent the student uses. State the colour of the precipitate that forms. reagent colour of precipitate Compounds containing I– are often contaminated by bromide ions, Br –. Identify a further reagent that the student could use to show that the precipitate formed in contained iodide ions. HOF is the only known molecule that contains only the elements hydrogen, oxygen and fluorine. Draw a ‘dot-and-cross’ diagram to represent the bonding in a molecule of HOF. Show the outer shell electrons only. HOF can be made by the reaction of F2 with ice at – 40 °C. The reaction is similar to the reaction of Cl 2 with cold water. Suggest an equation for the reaction of F2 with ice. HOF is an unstable compound and decomposes to form HF and O2. HOF → HF + 2 O2 ΔH = –139 kJ mol–1 Draw a fully labelled reaction pathway diagram on the axes provided to show the decomposition of HOF into HF and O2. enthalpy progress of reaction Pure HF is a colourless liquid at 273 K. The liquid contains HF molecules that have strong hydrogen bonds between them. Draw a fully labelled diagram to suggest how a hydrogen bond can form between two HF molecules. Interhalogen compounds, such as BrCl or IF5, contain two or more different halogen atoms that are covalently bonded. D is an interhalogen compound that contains only chlorine and fluorine. At 0 °C and 101 325 Pa, 1 dm3 of D has a mass of 4.13 g. Use the general gas equation to calculate the relative molecular mass, Mr, of D. Mr = Use your answer to to determine the molecular formula of D. If you were unable to calculate the Mr in , assume that the Mr is 130.5. This is not the correct value. molecular formula of D =

11. Group 17 → 11.2. The chemical properties of the halogen elements and the hydrogen halides

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P, Q and R all contain five carbon atoms. C P C N OH H3C CH2CH3 CH2CH3 C Q R O H3C CH2CH2CH3 C C OHC H H A student carries out several tests to distinguish between P, Q and R. Complete the table, identifying any observations for the reaction of each reagent with P, Q and R. If no reaction occurs, write ‘no reaction’. reagent observations with P Q R Na2,4-DNPH no reaction acidified K2Cr2O7no reaction Q is reduced by NaBH4. Write an equation for the reaction of Q with NaBH4. In your answer, use [H] to represent NaBH4. C5H10O + R exists as a pair of stereoisomers. Identify the type of stereoisomerism shown by R and draw the structure of the other stereoisomer. type of stereoisomerism stereoisomer of R The infra-red spectrum shown corresponds to one of P, Q or R. transmittance wavenumber / cm–1 Deduce which of the compounds, P, Q or R, produces this spectrum. Explain your reasoning. In your answer, identify any relevant absorptions in the infra-red spectrum and the bonds that correspond to these absorptions in the region above 1500 cm–1. compound explanation

17. Carbonyl compounds → 17.1. Aldehydes and ketones

14. Hydrocarbons → 14.2. Alkenes

11. Group 17 → 11.2. The chemical properties of the halogen elements and the hydrogen halides

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Allyl chloride is an important chemical used in the manufacture of plastics, pharmaceuticals and pesticides. Cl allyl chloride Give the systematic name of allyl chloride. Allyl chloride can be produced by many different methods. The most common method is chlorination of propene which proceeds via a free-radical substitution mechanism. Cl Cl 2 The initiation step in this reaction is the formation of chlorine radicals (Cl ●) from Cl 2 molecules. State the conditions required to initiate this reaction. The propenyl radical, CH2=CHCH2 ●, is formed in the first propagation step of the reaction. Write an equation to show the formation of CH2=CHCH2 ● in this propagation step. Explain why the free-radical substitution reaction gives a low yield of allyl chloride. Allyl chloride can also be formed by the following substitution reaction. Cl OH reagent X Suggest the identity of reagent X. A series of reactions starting from allyl chloride is shown. Cl Cl HO reaction 1 HCN and NaCN reaction 3 reaction 2 OH Cl CH3COO CH3COO CN CH3COO CH3COO Y Suggest a reagent that can be used in reaction1. In reaction2, the organic product of reaction1 is mixed with concentrated H2SO4 and an organic acid, and then heated under reflux. State the role of the concentrated H2SO4. Identify the organic acid used. role of the concentrated H2SO4 identity of the organic acid State the name of the mechanism that occurs in reaction3. The organic product of reaction3 is Y. Y can be hydrolysed using excess aqueous H2SO4 to form Z. The molecular formula of Z is C4H8O4. Draw the structure of Z. 2-bromo-1-chloropropane, CH3CHBrCH2Cl, is the major product of the reaction of allyl chloride with HBr. Cl Cl HBr and Br major product Cl Br minor product Explain why 2-bromo-1-chloropropane is the major product of this reaction.

11. Group 17 → 11.4. The reactions of chlorine

21. Organic synthesis → 21.1. Organic synthesis

14. Hydrocarbons → 14.1. Alkanes

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