Free NTA Chemistry Question and Answers — Questions and Answers
Question 1: What is the atomic number of carbon?
- 6 (Correct answer)
- 8
- 12
- 14
Correct answer: 6
The atomic number of an element is defined by the number of protons in the nucleus of an atom of that element. Carbon atoms always contain 6 protons, which uniquely identifies it as carbon on the periodic table. This number also dictates its electron configuration and fundamental chemical properties.
Question 2: What is the most common form of carbon found in nature?
- Graphite (Correct answer)
- Diamond
- Fullerenes
- Carbon Nanotubes
Correct answer: Graphite
Graphite is the most common and stable allotrope of carbon found in nature under standard conditions. It consists of layers of carbon atoms arranged in hexagonal rings, making it soft, slippery, and a good conductor of electricity. While diamond is also a natural form of carbon, it is much rarer and forms under extreme pressure and temperature.
Question 3: Which element is known for having the highest electronegativity?
- Oxygen
- Fluorine (Correct answer)
- Chlorine
- Nitrogen
Correct answer: Fluorine
Electronegativity is a measure of an atom's ability to attract shared electrons in a chemical bond. Fluorine is the most electronegative element on the periodic table because it has a small atomic radius and a high effective nuclear charge, strongly attracting electrons. This property makes it highly reactive, especially in forming ionic and polar covalent bonds.
Question 4: What is the pH of a neutral solution at 25°C?
- 1
- 7 (Correct answer)
- 14
- 0
Correct answer: 7
The pH scale measures the acidity or alkalinity of a solution, ranging from 0 to 14. A neutral solution, such as pure water at 25°C, has an equal concentration of hydrogen ions (H+) and hydroxide ions (OH-), resulting in a pH of 7. Solutions with a pH below 7 are acidic, and those above 7 are basic (alkaline).
Question 5: Which of the following is a strong acid?
- Acetic acid
- Hydrochloric acid (Correct answer)
- Citric acid
- Carbonic acid
Correct answer: Hydrochloric acid
A strong acid is one that completely dissociates into its ions when dissolved in water, meaning nearly all its molecules release hydrogen ions (H+). Hydrochloric acid (HCl) is a classic example of a strong acid, dissociating fully into H+ and Cl- ions. In contrast, acetic acid, citric acid, and carbonic acid are weak acids, which only partially dissociate.
Free NTA Chemistry Question and Answers
What is the atomic number of carbon?