9701_s21_qp_22
A paper of Chemistry, 9701
Questions:
5
Year:
2021
Paper:
2
Variant:
2
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1
A Group2 metal combines with bromine to form a crystalline solid, MBr2. Excess aqueous AgNO3 is added to a solution of MBr2 and a precipitate forms. The mixture is filtered. The precipitate is dried and the mass of the precipitate is recorded. State the formula and colour of the precipitate. Complete the equation to represent the reaction between MBr2 and AgNO3. MBr2 + AgNO3 →  A 0.250 g sample of pure MBr2 contains 8.415 × 10–4 mol MBr2. Calculate the relative formula mass, Mr, of MBr2. Use this to identify M. Show your working.  Mr =  M =  A sample of MBr2 is dissolved in water. Chlorine gas is then bubbled into the solution. Describe the observations for this reaction. Name the type of reaction that occurs when MBr2 reacts with chlorine gas. CompoundY is a pure insoluble solid which contains halide ions. A single reagent is added directly to compoundY to determine the halide ion present. Identify the reagent added. State the observation which would confirm that Y contains bromide ions. reagent observation  Separate 1.0 g samples of three different magnesium salts are tested in order to identify the anion present in each sample. Explain how the action of heat is used to identify which sample is: ● MgCO3 ● Mg(NO3)2 ● MgO. Complete the electron configuration of the magnesium cation present in these salts. 1s2 A sample of MgCO3is distinguished from a sample of Mg(OH)2by adding a small amount of each solid to HCl . State one similarity and one difference in these two reactions. similarity difference  
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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The strength of interaction between particles determines whether the substance is a solid, liquid or gas at room temperature. Lithiumsulfide, Li2S, is a crystalline solid with a melting point of 938 °C. It conducts electricity when it is molten. Give the formulae of the particles present in solid lithiumsulfide. Explain, in terms of the structure of the crystalline solid, why lithiumsulfide has a high melting point. Carbon monoxide, CO, is a gas at room temperature and pressure. It contains a coordinate bond. Explain what is meant by coordinate bond. Draw a ‘dot-and-cross’ diagram to show the arrangement of outer electrons in CO. Show the electrons belonging to the C atom as ×. Show the electrons belonging to the O atom as ●.  Nitrogen, N2, is also a gas at room temperature and pressure. Neither CO nor N2 is an ideal gas. State two assumptions that are made about the behaviour of particles in an ideal gas.  Explain why N2 does not behave as an ideal gas at very high pressures. Complete the table by naming all the types of intermolecular forces (van der Waals’) in separate samples of N2and CO. N2COnumber of electrons per molecule presence of a dipole moment   boiling point / °C –195.8 –191.5 intermolecular forces (van der Waals’)  Suggest why the bond in a molecule of CO contains a dipole moment. 
3. Chemical bonding  →  3.6. Intermolecular forces, electronegativity and bond properties
4. States of matter  →  4.1. The gaseous state: ideal and real gases and \( pV = nRT \)
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A large excess of 2-bromo-2-methylpropane is added to 0.0010 mol of NaOH, which contains a few drops of phenolphthalein indicator. A stopwatch is started as soon as the substances are mixed. The time taken for the pink colour to disappear is recorded. The experiment is repeated at different temperatures, keeping all concentrations and volumes of reagents constant. temperature / °C time taken for pink colour to disappear / s Explain what is meant by the term rate of reaction. The graph shows the energy distribution of molecules in a sample of 2‑bromo‑2‑methylpropane at 25 °C. Ea represents the activation energy for the reaction. proportion of molecules with a given energy molecular energy Ea Label the graph to show the proportion of 2‑bromo‑2‑methylpropane molecules which have sufficient energy to react. Use the same axes to sketch the distribution of energies of molecules in a sample of 2‑bromo‑2‑methylpropane at 50 °C. State the effect of an increase in temperature on Ea for this reaction. Draw the mechanism to show the reaction of 2‑bromo‑2‑methylpropane with OH–. Show the intermediate formed in this reaction. Include all charges, partial charges, lone pairs and curly arrows as appropriate. H3C CH3 CH3 Br C  Name the mechanism for this reaction. The original experiment is repeated at 25 °C with 2‑chloro‑2‑methylpropane instead of 2‑bromo‑2‑methylpropane. All other variables remain constant. Predict the effect of using 2‑chloro‑2‑methylpropane compared to 2‑bromo‑2‑methylpropane on the time taken for the pink colour to disappear. Explain your answer. 
8. Reaction kinetics  →  8.2. Effect of temperature on reaction rates and the concept of activation energy
14. Hydrocarbons  →  14.2. Alkenes
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The table shows the structural formulae of four compounds, A, B, C and D, with molecular formula C4H8. Complete the table by giving the systematic name of A, B, C and D. structural formula name A CH3CH2CH=CH2 B C C H CH3 H H3C C C C H CH3 H H3C D CH2=C(CH3)2  Explain what is meant by stereoisomerism. W is an alkene with formula C4H8. It reacts with HBr to form two possible carbocations, CH3C+(H)(CH2CH3) and H2C+CH2CH2CH3. Identify W as compound A, B, C or D. Draw the skeletal formula of the major organic product formed when HBr reacts with W. Explain why this is the major organic product.  A sample of propan‑1‑ol reacts with concentrated sulfuricacid to form propene. Identify the role of concentrated sulfuricacid in this reaction. AlcoholY reacts completely when warmed with acidified Cr2O7 2– to form Z. Z is distilled from the reaction mixture as soon as it is made. Tollens’ reagent is added to a sample of Z and warmed. A silver mirror forms. Name the type of reaction that occurs when Y reacts to form Z. Identify with a tick () the functional grouppresent in Z. functional group present in Z aldehyde ketone carboxylic acid  
13. An introduction to AS Level organic chemistry  →  13.1. Formulas, functional groups and the naming of organic compounds
16. Hydroxy compounds  →  16.1. Alcohols
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S is a secondary alcohol with molecular formula C4H10O. Draw the displayed formula of S.  S is converted to V in a three‑step reaction sequence. S C4H10O step 1 PBr3 T C4H9Br step 2 U C4H9CN step 3 dilute acid V In step1, the secondary alcoholS reacts with PBr3 to produce T, which has molecular formula C4H9Br. Give the systematic name of T. Name the type of reaction that occurs in step1. State the reagentand conditions for step2. Step3 involves heating C4H9CN with dilute acid to form V. Complete the equation for this reaction. C4H9CN + H+ + H2O →  An unlabelled sample contains either S, T or U. The sample produces the infrared spectrum shown. transmittance / % wavenumber / cm–1 Explain how this spectrum confirms that the unknown sample contains U. In your answer identify one relevant absorption in the infrared spectrum and the bond that corresponds to this absorption in the region above 1500 cm–1. 
16. Hydroxy compounds  →  16.1. Alcohols
22. Analytical techniques  →  22.1. Infrared spectroscopy
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