This question was attempted by majority of the candidates and the performance was good.
In (a)(i)-(iii), some candidates lost the mark in (i) because they wrote "any indicator" instead of mentioning the name of the indicator such as phenolphthalein, methyl orange or methyl red .
In (b), most candidates only calculated the new volume of the 0.010 moldm-3 HCI hence, lost the mark for the determination of the volume of distilled water that would be added to the original solution of 50cm3 of 0.1 0 moldm-3 solution.
The expected solution to the question was as follows:
CIVI (undiluted)
C2 V 2 (diluted)
Using dilution law: C1VI = C2 V2
V2 = C1V1 = 0.1 x 0.5
C2 0.010
= 500cm3
Volume of distilled water to be added to the original solution to make 0.01 moldm-3 = 500cm3 - 50cm3
= 450cm3
In (c), candidates wrote the formula of the gas instead of the name hence lost the mark for the question. The expected response from candidates was any of hydrogen chloride, ammonia or sulphur (IV) oxide.
