21: Consider the following statements :
1. Steam at 100 Degree Celsius and boiling water at 100 Degree Celsius contain same amount of heat.
2. Latent heat of fusion of ice is equal to the latent heat of vaporization of water.
3. In an air-conditioner, heat is extracted from the room-air at the evaporator coils and is rejected out at the condenser coils.
Which of these statements is/are correct?
(a) 1 and 2
(b) 2 and 3
(c) Only 2
(d) Only 3
Explanation:
Steam at 100 degree C contain more amount of heat than boiling water at 100 degree C. Latent heat of fusion of ice (80 cal/g) is less than latent heat of vaporization of water (536 cal/g).
22: Which one of the following statements is correct?
(a) Prions are the smallest free-living cells
(b) The cell wall of Mycoplasmas is made up of amino sugars
(c) Viroids consist of a single-stranded RNA molecule
(d) Rickettsias lack cell wall
Explanation:
Viroids are single stranded RNA molecules without protein coat causes different diseases like Chrysanthemum stunt. Prions are infectious protein bodies.
Mycoplasmas lack cell wall while Rickettsias possess cell wall.
23: What happens when alcohol is taken in excess?
(a) It destroys the liver
(b) It produces inflammation of the stomach
(c) It causes the heart to become weak
(d) All of the above
24: Consider the following statements:
1. During the process of osmosis, the solvent travels from concentrated solution to the diluted solution.
2. In the reverse osmosis, external pressure is applied to the dilute solution.
Which of the following statements given above is/are correct?
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Explanation:
Osmosis is movement of solvent molecules form a less concentrated solution (dilute solution) to high concentrated solution through a semi permeable membrane. For reverse osmosis an external pressure to the membrane has to be created. This technique is used in desalination of plants.
25: Vinegar is an aqueous solution of
(a) oxalic acid
(b) citric acid
(c) acetic acid
(d) hydrochloric acid