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17. Which of the following is NOT a 18. For which pair of titrations is methyl orange
characteristic of primary standards used (indicator range 2.9 - 4.6) BEST suited?
in titrimetric analysis?
(A) Strong acid - strong base AND
(A) High purity strong acid - weak base
(B) Stable in air (B) Strong base - weak acid AND weak
(C) Deliquescent acid - weak base
(D) Soluble (C) Strong acid - strong base AND
weak acid - weak base
(D) Strong acid - weak base AND
strong base - weak acid

19. 25.0 cm of an aqueous iron (II) salt is acidified with an equal volume of dilute sulphuric acid and
3
titrated against 0.02 mol dm-3 potassium manganate (VII) solution. The endpoint is 30.0 cm3.

2+ 4- 3+ 2+
+
5Fe (aq) + MnO (aq) + 8H (aq) ☞ 5Fe (aq) + Mn (aq) + 4H O (l)
2

The correct concentration of the iron (II) ions, in mol dm , is
-3
(A) 5 x 25.0
0.02 x 30.0

(B) 5 x 0.02 x 30.0
25.0

(C) 5 x 0.02 x 25.0
30.0

(D) 25.0
5 x 0.02 x 30.0

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02212010/SPEC/CAPE 2017