9701_s24_qp_23
A paper of Chemistry, 9701
Questions:
5
Year:
2024
Paper:
2
Variant:
3
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1
Explain the lack of reactivity of nitrogen gas, N2. Covalent bonds can be σ bonds or π bonds. Complete Table 1.1 to show the number of σ and π bonds in a molecule of N2 and to describe how the orbitals overlap to form σ and π bonds. Table 1.1 σ bond π bond number of bonds in N2 how the orbitals overlap A sample of Al reacts with an excess of Cl 2. State the oxidation number of Al in the product of the reaction. oxidation number of Al State what determines the maximum oxidation number of the Period 3 elements in their oxides. Separate samples of aluminium oxide, Al 2O3, and phosphorus(oxide, P4O10, react with an excess of NaOHat room temperature. Give the state of Al 2O3 and P4O10 at room temperature. Al 2O3 P4O10 Write an equation for the reaction of each oxide with an excess of NaOHat room temperature. Al 2O3 + P4O10 + The oxide of silicon reacts with calcium oxide in an addition reaction to produce calcium silicate, CaSiO3. The oxidation number of calcium in CaSiO3 is +II. Deduce the oxidation number of silicon in calcium silicate. oxidation number of silicon Calcium oxide can be made from calcium carbonate in a single-step reaction. Identify the type of reaction that occurs.
12. Nitrogen and sulfur  →  12.1. Nitrogen and sulfur
9. The Periodic Table: chemical periodicity  →  9.2. Periodicity of chemical properties of the elements in Period 3
3. Chemical bonding  →  3.4. Covalent bonding and coordinate (dative covalent) bonding
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N2reacts with H2in the Haber process, as shown in reaction 1. reaction 1 N2+ 3H22NH3ΔH = –x kJ mol–1 Table 2.1 shows the different conditions used to produce three equilibrium mixtures, A, B and C. Table 2.1 A B C initial molar ratio of N2 : H2 added 1 : 3 1 : 3 1 : 3 temperature / °C pressure / atm iron present in mixture no yes no percentage yield of NH3at equilibrium x y Describe and explain the change, if any, to the percentage yield of NH3produced in B compared to A. Describe and explain the change, if any, to the percentage yield of NH3produced in C compared to A. Describe and explain the change to the rate of the forward reaction that occurs to establish the equilibrium in C compared to A. You do not need to refer to the Boltzmann distribution in your answer. Write an expression for the equilibrium constant, Kp, for reaction 1. State the units. Kp = units Equilibrium mixture D is made when 1.0 mol of N2and 3.0 mol of H2are added to a sealed container at 750 °C and 1000 atm and left to reach equilibrium. This mixture contains 1.16 mol of NH3. Calculate the mole fraction of NH3in D. mole fraction of NH3= The mole fraction of N2is 0.625 in a new equilibrium mixture, E. Calculate the partial pressure of N2in E when the total pressure is 1000 atm. partial pressure of N2= atm When oxides of nitrogen escape into the atmosphere they may be involved in: • formation of acid rain from sulfur dioxide • formation of photochemical smog. Identify the role of NO and NO2 in the formation of H2SO4 from SO2 in the atmosphere to produce acid rain. Use relevant equations to support your answer. Outline how NO and NO2 may contribute to the formation of photochemical smog.
7. Equilibria  →  7.1. Chemical equilibria: reversible reactions, dynamic equilibrium
12. Nitrogen and sulfur  →  12.1. Nitrogen and sulfur
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3
Write an equation to show the reaction for the standard enthalpy change of formation of H2O. Include state symbols. Water is one of the products in the reaction of B2O3 and NH3, as shown in reaction 2. reaction 2 B2O3 + 2NH3 2BN + 3H2O Table 3.1 shows information about the standard enthalpy change of formation, ΔH f o, of some substances. Table 3.1 substance ΔH f o / kJ mol–1 B2O3 –1264 NH3 – 46 BN –134 H2O –286 Calculate the enthalpy change, ∆H, for reaction 2 using the data from Table 3.1. ∆H = kJ mol–1 Boron carbide is a hard crystalline solid that has a melting point greater than 2000 °C. Suggest the structure and bonding in boron carbide. 100 g of pure boron carbide contains 78.26 g of boron. Calculate the empirical formula of boron carbide. Show your working. empirical formula of boron carbide
5. Chemical energetics  →  5.1. Enthalpy change, \(\Delta H\)
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4
NH3reacts with HCl to produce NH4Cl , as shown. NH3+ HCl NH4Cl Draw a diagram to show the ionic, covalent and coordinate bonding present in a formula unit of NH4Cl . An exothermic reaction occurs when NH4 +is added to OH–. Identify the type of reaction. Construct an ionic equation for the reaction of NH4 + and OH–. Substitution reactions of NH3 and OH– with halogenoalkanes both involve a lone pair of electrons. Name the role of NH3 and OH– in these reactions. Suggest which species, NH3 or OH–, is more reactive during these reactions. Explain your answer. When 2-bromo-2-methylpropane reacts with OH–, two mechanisms, SN1 and SN2, both occur. The SN2 mechanism has a slower rate. shows the reaction pathway diagram for the SN1 mechanism. Sketch a graph on to show the reaction pathway for the SN2 mechanism. intermediate reactants progress of reaction products energy / kJ mol-1 Complete to show the mechanism for the SN1 reaction that occurs when CH3CHBrC2H5 reacts with NH3 to produce CH3CH(NH2)C2H5. Include charges, dipoles, lone pairs of electrons and curly arrows, as appropriate. Br C2H5 C2H5 C H CH3 C2H5 C+ H CH3 H C N+ H H CH3 H H2N C2H5 C H CH3 Identify the inorganic product that forms in the reaction in . Give the systematic name for the organic product CH3CH(NH2)C2H5. Complete Table 4.1 by drawing the structural formula of the intermediate that is formed when 2-bromo-2-methylpropane reacts in an SN1 reaction. Table 4.1 2-bromobutane 2-bromo-2-methylpropane structural formula of intermediate in SN1 reaction C2H5 C+ H CH3 Identify the halogenoalkane in Table 4.1 that has the greater tendency to react using the SN1 mechanism. Explain your answer.
15. Halogen compounds  →  15.1. Halogenoalkanes
14. Hydrocarbons  →  14.2. Alkenes
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M reacts to form R by the addition of one reagent, as shown in . HO reagent M R HO Identify the reagent and conditions for this reaction. R is also made from M by two steps, as shown in . HO step 2 M R HO Br step 1 Q Br Identify the reagents and conditions for steps 1 and 2 in . step 1 step 2 Name the mechanism for step 1 in . The infrared spectrum of R is shown in . wavenumber / cm–1 transmittance / % Table 5.1 bond functional groups containing the bond characteristic infrared absorption range (in wavenumbers) / cm–1 C–O hydroxy, ester 1040–1300 C=C aromatic compound, alkene 1500–1680 C=O amide carbonyl, carboxyl ester 1640–1690 1670–1740 1710–1750 C≡N nitrile 2200–2250 C–H alkane 2850–2950 N–H amine, amide 3300–3500 O–H carboxyl hydroxy 2500–3000 3200–3650 Use the absorptions in the region above 1500 cm–1 in Table 5.1 when answering this question. • Add F to to identify the peak that is present in an infrared spectrum of both Q and R. Identify the bond that corresponds to the absorption for F. • Add G to to identify the peak that is not present in an infrared spectrum of Q. Identify the bond that corresponds to the absorption for G. Y is made from Q in a three-step reaction. Br Q W X Y Br KCN in ethanol / heat reducing agent Z step 2 step 3 step 1 O HO O OH HO OH Draw the structure of W in the box in . In step 2, W is heated with HCl to produce X and an inorganic product. Identify the formula of the inorganic product. In step 3, X reacts with reducing agent Z to produce Y. Complete the equation for the reaction of X with Z. Use a molecular formula to represent the organic product. Use [H] to represent one atom of hydrogen from Z. …… C8H12O4 + ……[H] Identify Z.
15. Halogen compounds  →  15.1. Halogenoalkanes
22. Analytical techniques  →  22.1. Infrared spectroscopy
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