Option “D” is correct Nitrogen is a chemical element with symbol N and atomic number 7. It was first discovered and isolated by Scottish physician Daniel Rutherford in 1772.
262. Using which of the following processes can one separate a solute from its solution?
Option “B” is correct Cobalt oxide is added to glass to gave it blue colour.
264. Which of the following elements has the lowest melting point?
1. Sodium
2. Tin
3. Radon
4. Radium
Option “C” is correct Radon has lowest melting point among the following elements.
265. Atomic number of which of the following elements is greater than that of Fluorine?
1. Sodium
2. Beryllium
3. Nitrogen
4. Boron
Option “A” is correct Atomic Number of Beryllium is 4, Boron is 5, Nitrogen is 7, Fluorine is 9 and Sodium is 11. Hence, the atomic number of Sodium is higher than that of Fluorine.
266. Which of the following induces souring of milk?
Option “D” is correct Milk contains a sugar called lactose. It also contains harmless bacteria called lactobacillus, which uses lactose for energy and creates lactic acid as a by-product. It is the lactic acid which makes milk taste sour.
267. What is the net charge on Calcium fluoride?
1. 1+
2. 0
3. 1–
4. 2–
Option “B” is correct The net charge of the ionic compound is zero. It is composed of one ion of calcium with a positive two charge and two ions of fluorine with a negative one charge on each. The charges cancel out, leaving the compound with no net charge.
268. Which of the following is a greenhouse gas or a gas which can deplete the ozone layer?
1. B2H6
2. NF3
3. CCl3F
4. C6H6
Option “C” is correct Trichlorofluoromethane, CCl3F consists of a centrally placed carbon atom with three chlorine atoms and one fluorine atom arranged approximately (the bond lengths are different) at the points of a tetrahedron around it. Trichlorofluoromethane is a greenhouse gas and ozone depleter.
269. Which of the following is not soluble in water?
Option “A” is correct Lead Sulphate is not soluble in water.
270. Ethylene is a ______ molecule.
1. Polar
2. Ionic
3. Covalent
4. Nonpolar
Option “D” is correct Ehthylene is a hydrocarbon which has the formula C2H4 since the double bond is between two carbon atoms so there is no difference in electronegativity.That’s why the shared pair of electron come lie in between those to carbon atoms, so ethylene is non polar.
