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Chemistry · May / June 2020 · Paper 41 · Question 4

0620

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This question is about reactions of bases and acids.

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  • 4(a)[2]

    (damp) litmus

    (turns) blue

  • 4(b)(i)[1]

    proton acceptor

  • 4(b)(ii)[1]

    Above pH 7 up to 11

  • 4(b)(iii)[3]

    blue precipitate

    precipitate dissolves

    deep blue solution remains

  • 4(c)(i)[1]

    neutralisation

  • 4(c)(ii)[2]

    Na2SO4

    2H2O

  • 4(d)(i)[1]

    methyl orange

  • 4(d)(ii)[3]

    25.0

    M1 mol of NaOH

    0.0400
    0.001 00
    mol

    1000

    M1

    0.001

    M2 mol of H2SO4

    0.0005 00
    2

    2

    M3 M2 1000

    1000

    0.0005
    0.025

    (mol / dm3)

    20.0

    20.0

    allow ecf

  • 4(d)(iii)[2]

    M1 use of 40 g/mol

    M2 40 × 0.04 = 1.6 (g/dm3)

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