Chemistry · Oct / Nov 2025 · Paper 41 · Question 3
0620
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The question as text
A student makes crystals of the salt sodium sulfate, Na2SO4 . The student reacts 0.200 mol / dm3 dilute sulfuric acid, H2SO4(aq), with aqueous sodium hydroxide, NaOH(aq). The student uses the following steps. step 1 The student places 40.0 cm3 of NaOH(aq) into a conical flask. This volume contains 0.0100 moles of NaOH. step 2 The student adds a few drops of methyl orange indicator to the NaOH(aq) in the conical flask. step 3 The student adds 0.200 mol / dm3 H2SO4(aq) to the flask until the end-point is reached. step 4 The student transfers the mixture from the conical flask to an evaporating basin and obtains dry crystals.
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3(a)[2]
M1 2H2O
M2 state symbols (aq) and (l)
3(b)[1]
neutralisation
3(c)[1]
0.0100 × 1000 ‣ 40 = 0.25(0)
3(d)[1]
burette
3(e)[2]
M1 mol H2SO4 needed = 0.0100 ‣ 2 = 0.005(00)
M2 vol of H2SO4 needed = 0.005(00) ‣ 0.200 × 1000 = 25 (cm3)
3(f)[2]
M1 yellow
M2 orange
3(g)[1]
repeat steps 1 and 3 without indicator
3(h)(i)[2]
M1 (a solution containing the) maximum concentration of a solute dissolved in the solvent
M2 at a specified temperature
3(h)(ii)[1]
solubility decreases as temperature decreases
3(h)(iii)[1]
none
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