Chemistry Form Two Pre Necta I Exam 2026 With Marking Schemes St. Monica Wino Girls’ Secondary School
Chemistry
Form Two Pre Necta I Exam 2026 With Marking Schemes St.
Monica Wino Girls’ Secondary School
6. A
chemist set experiments with the following conditions:
(a) Iron
nail A was placed in boiled water and oil.
(b) Iron
nail B was placed in wet cotton wool.
(c) Iron
nail C was placed in cotton wool covered by anhydrous calcium chloride.
(d) Iron
nail D was placed in dry air.
(i) What
was the aim of the experiment?
(ii)
Predict the expected observation for each nail after 4 – 5 days.
(iii) What
property of anhydrous calcium chloride makes it suitable for this experiment?
(iv) What
was the role of oil in this experiment?
(v)
Outline three conditions necessary for the observed phenomena to occur.
7. (a)
Medical doctors sometimes use X-rays to view patient’s bodies. These rays
interact mainly with atoms in the patient’s bones.
(i) Which
sub-atomic particle is responsible for this interaction?
(ii) Why
do you think this particle is important in medical imaging?
(b) The
percentage abundance of isotopes of a certain element are in the ratio of 3:2:1
and their
masses are
16, 17 and 18 respectively. Calculate the relative atomic mass of an element.
