Railway Science (Chemistry-Chemical Properties)

Total Questions: 52

51. Burning Magnesium ribbon produces white ash, which dissolves in water to form ____. (chemical reaction) [RRB ALP Tier - I (21/08/2018) Evening]

Correct Answer: (a) Magnesium Hydroxide
Solution:

When magnesium metal burns in the presence of oxygen it reacts with oxygen to form a compound called magnesium oxide. It is a type of exothermic reaction. MgO (Magnesium oxide)+ H₂O (water) → Mg(OH)₂ (Magnesium hydroxide). Magnesium oxide (MgO), Magnesium Sulphate (MgSO₄).

52. Which of the following is a chemical change? [RRB ALP Tier - I (29/08/2018) Morning]

Correct Answer: (b) Butter turning rancid
Solution:

Chemical Change - A type of change in which a new substance is formed; Changes are mostly irreversible; Examples - Rusting of iron, Digestion of food, Baking a cake, Rotting of fruits, Decomposition of waste.
Physical Change - A type of change in which a new substance is not formed; Changes are reversible; Examples - Making dry ice from CO₂ , Magnetisation of iron, Heating a platinum wire, Boiling water, Vaporizing liquid nitrogen.