9701_s13_qp_21 - revisedeck

9701_s13_qp_21

A paper of Chemistry, 9701

Questions:

5

Year:

2013

Paper:

2

Variant:

1

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1

A sample of a fertiliser was known to contain ammonium sulfate, (NH4)2SO4, and sand only. A 2.96 g sample of the solid fertiliser was heated with 40.0 cm3 of NaOH, an excess, and all of the ammonia produced was boiled away. After cooling, the remaining NaOHwas exactly neutralised by 29.5 cm3 of 2.00 mol dm–3 HCl. In a separate experiment, 40.0 cm3 of the original NaOHwas exactly neutralised by 39.2 cm3 of the 2.00 mol dm–3 HCl. Write balanced equations for the following reactions. NaOH with HCl (NH4)2SO4 with NaOH Calculate the amount, in moles, of NaOH present in the 40.0 cm3 of the original NaOHthat was neutralised by 39.2 cm3 of 2.00 mol dm–3 HCl. Calculate the amount, in moles, of NaOH present in the 40.0 cm3 of NaOHthat remained after boiling the (NH4)2SO4. Use your answers to and to calculate the amount, in moles, of NaOH that reacted with the (NH4)2SO4. For Examiner’s Use Use your answers to and to calculate the amount, in moles, of (NH4)2SO4 that reacted with the NaOH. Hence calculate the mass of (NH4)2SO4 that reacted. Use your answer to to calculate the percentage, by mass, of (NH4)2SO4 present in the fertiliser. Write your answer to a suitable number of signiﬁ cant ﬁ gures. The uncontrolled use of nitrogenous fertilisers can cause environmental damage to lakes and streams. This is known as eutrophication. What are the processes that occur when excessive amounts of nitrogenous fertilisers get into lakes and streams? Large quantities of ammonia are manufactured by the Haber process. Not all of this ammonia is used to make fertilisers. State one large-scale use for ammonia, other than in the production of nitrogenous fertilisers.

12. Nitrogen and sulfur → 12.1. Nitrogen and sulfur

11. Group 17 → 11.4. The reactions of chlorine

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2

For Examiner’s Use Ammonium nitrate fertiliser is manufactured from ammonia. The ﬁ rst reaction in the manufacture of the fertiliser is the catalytic oxidation of ammonia to form nitrogen monoxide, NO. This is carried out at about 1 × 103 kPa (10 atmospheres) pressure and a temperature of 700 to 850 °C. 4NH3+ 5O24NO+ 6H2O∆H = –906 kJ mol–1 Write the expression for the equilibrium constant, Kp, stating the units. Kp = units What will be the effect on the yield of NO of each of the following? In each case, explain your answer. increasing the temperature decreasing the applied pressure For Examiner’s Use The standard enthalpy changes of formation of NH3and H2Oare as follows. NH3, ∆Hf = –46.0 kJ mol–1 H2O, ∆Hf = –242 kJ mol–1 Use these data and the value of given below to calculate the standard enthalpy change of formation of NO. Include a sign in your answer. 4NH3+ 5O24NO+ 6H2O∆H = –906 kJ mol–1

12. Nitrogen and sulfur → 12.1. Nitrogen and sulfur

5. Chemical energetics → 5.1. Enthalpy change, \(\Delta H\)

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3

For Examiner’s Use This question refers to the elements in the section of the Periodic Table shown below. H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca transition elements Ga Ge As Se Br Kr From this list of elements, identify in each case one element that has the property described. Give the symbol of the element. An element that ﬂ oats on cold water and reacts readily with it. An element that forms an oxide that is a reducing agent. The element that has the smallest ﬁ rst ionisation energy. The element which has a giant molecular structure and forms an oxide which has a simple molecular structure. The element in Period 3 (Na to Ar) that has the smallest anion. The element in Period 3 (Na to Ar) which forms a chloride with a low melting point and an oxide with a very high melting point. For Examiner’s Use Use the elements in Period 3 (Na to Ar) in the section of the Periodic Table opposite to identify the oxidereferred to below. In each case, give the formula of the oxide. An oxide which when placed in water for a long time has no reaction with it. An oxide which dissolves readily in water to give a strongly alkaline solution. Two acidic oxides formed by the same element. and An oxide which is amphoteric. Fluorine reacts with other elements in Group VII to form a number of different compounds. Two such compounds and their boiling points are given in the table. compound Cl F3 BrF3 boiling point / °C The two molecules have similar electronic conﬁ gurations. Showing outer electrons only, draw a 'dot-and-cross' diagram of the bonding in Cl F3. The two molecules have the same shape. Suggest why the boiling points are signiﬁ cantly different.

9. The Periodic Table: chemical periodicity → 9.2. Periodicity of chemical properties of the elements in Period 3

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4

For Examiner’s Use Organic chemistry is the chemistry of carbon compounds. The types of organic reactions that you have studied are listed below. addition elimination hydrolysis oxidation reduction substitution Addition and substitution reactions are further described as follows. electrophilic nucleophilic free radical Complete the table below. Fill in the central column by using only the types of reaction given in the lists above. Use both lists when appropriate. In the right hand column give the formulaof the reagentyou would use to carry out the reaction given. organic reaction type of reaction reagentCH3CH2CH2CH2Br → CH3CH2CH2CH2NH2 CH3CH2CH2CH2OH → BrCH2CH2CH2CH2OH CH3COCH3 → CH3C(OH)(CN)CH3 CH3CH(OH)CH2CH3 → CH3CH=CHCH3

13. An introduction to AS Level organic chemistry → 13.2. Characteristic organic reactions

21. Organic synthesis → 21.1. Organic synthesis

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5

For Examiner’s Use Crotonaldehyde, CH3CH=CHCHO, occurs in soybean oils. In the boxes below, write the structural formula of the organic compound formed when crotonaldehyde is reacted separately with each reagent under suitable conditions. If you think no reaction occurs, write 'NO REACTION' in the box. reaction reagent product A Br2 in an inert organic solvent B PCl 3 C H2 and Ni catalyst D NaBH4 E K2Cr2O7 / H+ Crotonaldehyde exists in more than one stereoisomeric form. Draw the displayed formulae of the stereoisomers of crotonaldehyde. Label each isomer. For Examiner’s Use Draw the skeletal formula of crotonaldehyde. The product of reaction E in the table opposite will react with a solution containing acidiﬁ ed manganate(ions. Draw the structural formulae of the organic products when the reagent is cold, dilute; hot, concentrated.

13. An introduction to AS Level organic chemistry → 13.1. Formulas, functional groups and the naming of organic compounds

14. Hydrocarbons → 14.2. Alkenes

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