311: The temperature for pasteurisation of milk is selected so as to:
(a) Kill the micro organisms
(b) Kill all bacteria
(c) Store it for long time without coagulation
(d) Kill the micro organisms and other harmful bacteria
312: With reference to ionic compounds, consider the following statements:
1. Ionic compounds are insoluble in alcohol.
2. Ionic compounds in the solid state are good conductors of electricity.
Which of these statements is/are correct?
(a) Only 1
(b) Only 2
(c) Both 1 and 2
(d) Neither 1 nor 2
Explanation:
Ionic compounds are highly soluble in water but are not soluble in organic solvents like alcohol, ether, acetone etc. Ionic compounds are good conductors in soluble state because of availability of free ions.
313: Which one of the following statements is not correct?
(a) The presence of NaCl increases the rate of setting of Plaster of Paris
(b) Gypsum is added to the cement to slow down its rate of setting
(c) All alkaline earth metals form hydrated salts
(d) Barium and Strontium are found free in nature
Explanation:
Gypsum is used for making 'Plaster of Paris'. It is prepared by heating Gypsum at 390 k. So the statement 'Presence of NaCl increases the rate of setting of Plaster of Paris is not correct.
314: Consider the following:
1. Birds
2. Dust blowing
3. Rain
4. Wind blowing
Which of the above spread plant diseases?
(a) 1 and 3 only
(b) 3 and 4 only
(c) 1, 2 and 4 only
(d) 1, 2, 3 and 4
315: In high mountain regions bleeding through nose occurs because:
(a) The pressure of the blood capillaries is higher than the outside pressure
(b) The pressure at high altitudes is greater than that in the plains
(c) The blood pressure increases at high altitudes
(d) The blood pressure decreases at high altitudes