1. Which of the following elements is a noble gas?
Answer:
Explanation:
Neon belongs to Group 18 and is a noble gas.
2. The compound used as an antiseptic as well as a disinfectant is:
Answer:
Explanation:
Boric acid has mild antiseptic and disinfectant properties.
3. Which of the following elements is a metalloid?
Answer:
Explanation:
Silicon has properties intermediate between metals and non-metals, classifying it as a metalloid.
4. The most electronegative element is:
Answer:
Explanation:
Fluorine is the most electronegative element in the periodic table.
5. Which p-block element is used in making LEDs?
Answer:
Explanation:
Gallium is used in the production of LEDs due to its semiconducting properties.
6. Which of the following gases is responsible for the greenhouse effect?
Answer:
Explanation:
Carbon dioxide is a major greenhouse gas responsible for global warming.
7. Phosphorus exists in several allotropic forms except:
Answer:
Explanation:
White, red, and black are the primary allotropes of phosphorus. Blue phosphorus is not a recognized allotrope.
8. The gas used in the manufacture of vanaspati fat is:
Answer:
Explanation:
Hydrogenation of vegetable oils, using hydrogen gas, results in vanaspati fat.
9. Which halogen is a liquid at room temperature?
Answer:
Explanation:
Bromine is the only halogen that is a liquid at room temperature.
10. The p-block element that is a lustrous, grey-white, hard metal and can form a protective oxide layer is:
Answer:
Explanation:
Aluminum is a lustrous metal that forms a protective oxide layer when exposed to air.
11. Which compound is used as a preservative for food?
Answer:
Explanation:
Benzoic acid and its salts are used as food preservatives.
12. Which of the following is not an allotrope of carbon?
Answer:
Explanation:
Galena is lead sulfide and not an allotrope of carbon.
13. The gas that causes tears when onions are cut is:
Answer:
Explanation:
When onions are cut, an enzyme reacts with amino acid sulfoxides to produce sulfenic acid, which then quickly converts to sulfur dioxide, causing tears.
14. Which of the following elements has the maximum atomic size?
Answer:
Explanation:
As we move down the group in the periodic table, atomic size increases. Among the given options, antimony has the largest atomic size.
15. The compound used in photography is:
Answer:
Explanation:
Silver bromide is sensitive to light and is used in photographic films.
16. The most abundant gas in the Earth's atmosphere is:
Answer:
Explanation:
Nitrogen constitutes about 78% of the Earth's atmosphere.
17. Which gas is responsible for the depletion of the ozone layer?
Answer:
Explanation:
CFCs are responsible for ozone layer depletion.
18. The element used for dating archaeological artifacts is:
Answer:
Explanation:
Carbon-14 isotope is used for radiocarbon dating.
19. Which of the following elements can expand its valence shell to accommodate more than eight electrons?
Answer:
Explanation:
Elements such as sulphur can have expanded octets due to empty d orbitals.
20. An example of a noble gas compound is:
Answer:
Explanation:
Xenon hexafluoride (XeF4) is a compound formed by the noble gas xenon.