You will devise chemical tests to distinguish between the two possible identities given for each of compounds FB 6, FB 7, FB 8 and FB 9. In each case you should: - use a 1 cm depth of the solution of the unknown compound in a test-tube - use a boiling tube if you need to warm a mixture - use a spatula measure of the unknown solid - record details of your test(s) and your observations - state your conclusion about the identity of the compound. (i) FB 6 is either aqueous chromium(III) sulfate or aqueous iron(II) sulfate. FB 6 is ................................................... (ii) FB 7 is either dilute hydrobromic acid or dilute nitric acid. If you select a test that gives a negative result, then you must carry out a further test that gives a positive result. FB 7 is ................................................... (iii) FB 8 is either magnesium carbonate or zinc carbonate. FB 8 is ................................................... (iv) FB 9 is either aqueous methanol or aqueous ethanol. Note: FB 9 is flammable and should not be heated with a flame. (When carrying out your test you may need to leave the reaction mixture to stand.) FB 9 is ................................................... Qualitative analysis notes

Chemistry

IGCSE&ALevel

CAIE

Exam No：9701_s24_qp_34 Year：2024 Question No：(b)

Answer:

Knowledge points:

7.1.1.1 understand what is meant by a reversible reaction

7.1.1.2 understand what is meant by dynamic equilibrium in terms of the rate of forward and reverse reactions being equal and the concentration of reactants and products remaining constant

7.1.1.3 understand the need for a closed system in order to establish dynamic equilibrium

7.1.10 describe and explain the conditions used in the Haber process and the Contact process, as examples of the importance of an understanding of dynamic equilibrium in the chemical industry and the application of Le Chatelier’s principle

7.1.2 define Le Chatelier’s principle as: if a change is made to a system at dynamic equilibrium, the position of equilibrium moves to minimise this change

7.1.3 use Le Chatelier’s principle to deduce qualitatively (from appropriate information) the effects of changes in temperature, concentration, pressure or presence of a catalyst on a system at equilibrium

7.1.4 deduce expressions for equilibrium constants in terms of concentrations,

7.1.5 use the terms mole fraction and partial pressure

7.1.6 deduce expressions for equilibrium constants in terms of partial pressures,

7.1.7 use the expressions to carry out calculations (such calculations will not require the solving of quadratic equations)

7.1.8 calculate the quantities present at equilibrium, given appropriate data

7.1.9 state whether changes in temperature, concentration or pressure or the presence of a catalyst affect the value of the equilibrium constant for a reaction

Answer:

Knowledge points:

Solution:

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