(a) Magnesium ribbon should be cleaned before burning at air because:
i. Magnesium is a very reactive metal.
ii. When it is stored, it forms a layer of magnesium oxide (MgO) by reacting with oxygen.
iii. This layer of MgO stops the further reaction of magnesium with oxygen.
iv. Thus, magnesium ribbon should be cleaned to before burning to air to remove this layer
(b) Iron should be protected from the moist air because:
i. When iron (a metal) is attacked by moist air (moisture), it is said to corrode.
ii. This process is called corrosion or rusting of iron.
iii. Rusting of iron causes damage to car bodies, bridges, iron railings to all objects made of iron.
iv. Every year a big amount of money is spent to replace damaged iron.
v. Hence, we should protect iron from moist air.
