CBSE Class 10 Science Optional Questions with Answers
41 Which of the following pairs of reactants will go undergo a displacement reaction?
Answer: CuSO4 + Fe
42 Galvanisation is a method of protecting steel and iron from rusting by coating them with a thin layer of
Answer: Zinc
44 An element X is soft and can be cut with the help of a knife. It is very reactive to air and cannot be kept open in the air. It reacts vigorously with water. Identify the element from the following:
Answer: Na
45 Some fruits like mango, lemon, raw grapes, orange, etc., have a sour taste due to the presence of:
Answer: Citric acid
46 Before burning in air, the magnesium ribbon is cleaned by rubbing with a sand paper to:
Answer: Remove the layer of magnesium carbonate from the ribbon surface
47 In a chemical reaction between sulphuric acid and barium chloride solution the white precipitates formed are of:
Answer: Barium sulphate
48 The respiration process during which glucose undergoes slow combustion by combining with oxygen in the cells of our body to produce energy, is a kind of:
Answer: Exothermic process