41. What is the name of the process where fatty foods become rancid?
a) Corrosion
b) Oxidation
c) Reduction
d) Hydrogenation
b) Oxidation
Explanation:
Rancidity is the aerial oxidation of fats and oils in food, resulting in an unpleasant taste and smell.
42. Which of the following gas can be used for storage of fresh sample of an oil for a long time:
i. Carbon dioxide
ii. Nitrogen
iii. Hydrogen
iv. Helium
a) i and iv
b) ii and iii
c) ii and iv
d) none of the above
c) ii and iv
Explanation:
Inert gases like Nitrogen and Helium are used to create a non-reactive atmosphere, preventing oxidation and preserving oily foods.
43. Reema took 5ml of lead nitrate solution in a beaker and added approximately 4ml of potassium iodide solution to it, what would she observe?
a) Solution turned red
b) Yellow precipitate was formed
c) White precipitate was formed
d) Reaction mixture became hot
b) Yellow precipitate was formed
Explanation:
The reaction between lead(II) nitrate and potassium iodide produces a bright yellow solid precipitate of lead(II) iodide (PbI2).
44. A student while burning a magnesium ribbon in air collected the product in a wet watch glass, the new product obtained was:
a) Magnesium oxide
b) Magnesium carbonate
c) Magnesium hydroxide
d) Magnesium chloride
Answer – c) Magnesium hydroxide
Burning magnesium forms magnesium oxide (MgO), which then reacts with the water on the watch glass to form magnesium hydroxide (Mg(OH)2).
45. The chemical formula for plaster of paris is:
a) CaSO4
b) CaSO4H2O
c) CaSO41/2 H2O
d) 2 CaSO4H2O
Answer – c) CaSO41/2 H2O
Explanation:
Plaster of Paris is calcium sulphate hemihydrate, meaning it has half a molecule of water of crystallization per formula unit.
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