What is the usual property of oxides of Group 3 and 4?
Correct Answer:
(A)
Basic and Acidic
The usual property of oxides of Group 3 and 4 of the periodic table are basic and acidic. These oxides are amphoteric (able to react both as a base and as an acid).
Ques:
32
Consider the following statements with reference to the periodic table of chemical elements :
1. Ionization potential gradually decreases along a period
2. In a group of elements, electron affinity decreases as the atomic weight increases
3. In a given period, electronegativity decreases as the atomic number increases
Which of these statement (s) is/are correct ?
Correct Answer:
(B)
2 only
The ionization energies are dependent upon the atomic radius. Since going from left to right across a period in the periodic table, the atomic radius decreases and the ionization potential increases while ionization potential decreases as one moves down a given group. In a group of elements, from top to bottom the electron affinity decreases as the atomic weight increases. As one moves trend- wise from left to right across a period in the periodic table, the electro-negativity increases due to the stronger attraction that the atoms obtain as the nuclear charge increases.
Ques:
33
Which is the most reactive metal ?
Correct Answer:
(D)
Potassium
Among the given options, Potassium is the most reactive metal. The given metals in order of reactivity are- Potassium (K) > Sodium (Na) > Calcium (Ca) > Iron (Fe).
Ques:
34
Which one of the following is the hardest metal?
Correct Answer:
(D)
Tungsten
Among all natural materials, diamond is the hardest (which is non-metal) whereas, among the metals, Tungsten is the hardest.
Ques:
35
Which one of the following materials is very hard and very ductile ?
Correct Answer:
(D)
Nichrome
Nichrome (NiCr, nickel-chrome, chrome-nickel, etc.) generally refers to any alloy of Nickel, Chromium and often Iron and/or other elements or substances. Nichrome is very hard and very ductile material. It has high specific resistively and minimum temperature coefficient. It also has the ability to operate at high temperature. Nichrome alloys are typically restorations (fillings) and in other applications.
Ques:
36
The heaviest natural element is ?
Correct Answer:
(A)
Uranium
Uranium is the heaviest naturally occurring element with an atomic no. of 92. It is a pure form of silver-coloured heavy metal. Its most common isotope Uranium-238 has a nucleus containing 92 protons and 146 neutrons. It has a density of 19.05 g/cm3.
Ques:
37
The chemical structure of the pearl is –
Correct Answer:
(A)
Calcium Carbonate
The chemical composition of pearl is 85% Calcium Carbonate (Aragonite), 10-14% Conchiolin and 2-4% of water (CaCO3 and H2O). Conchiolin is a protein.
Ques:
38
What are Rubies and Sapphires chemically known as?
Correct Answer:
(B)
Aluminium Oxide
Aluminium Oxide is a chemical compound of Aluminium and Oxygen with the chemical formula Al2O3. Corundum is the most common naturally occurring crystalline form of Aluminium Oxide. Rubies and Sapphires are gem-quality in forms of Corundum which owe their characteristic colours to trace impurities.
Ques:
39
Consider the following statements:
Assertion (A) : Sodium metal is stored under kerosene.
Reason (R) : Metallic sodium melts when exposed to air.
(a) Both
(A) and (R) are true, and (R) is the correct explanation of
(A).
(b) Both
(A) and (R) are true, but (R) is not a correct explanation of
(A).
Correct Answer:
(C)
Sodium is kept in kerosene to prevent it from coming in contact with oxygen present in the air. If this happens, it will react with the oxygen and form sodium oxide. This is a strongly exothermic reaction and a lot of heat is generated. Thus, Sodium is kept under kerosene.
Ques:
40
These days yellow lamps are frequently used as street light. Which one of the following is used in these lamps :
Correct Answer:
(A)
Sodium
There are 2 types of street light lamps which are used by municipalities. They are sodium vapor and mercury vapor lamps. The mercury vapor lamps have usually a white ambient light and sodium vapor lamps have orange/yellow light. Compared to LPS (Low-pressure sodium) lamps, high- pressure sodium lamps tend to have a longer life, less lumen per watt efficiency and most importantly a higher colour rendering index.