AS Associate Of Science In Chemistry 1 — Questions and Answers
Question 1: What is the number of protons in an atom called?
- Mass number
- Atomic mass
- Atomic number (Correct answer)
- Neutron number
Correct answer: Atomic number
The atomic number is the number of protons in the nucleus of an atom and uniquely identifies each chemical element.
Question 2: Which type of bond results from the electrostatic attraction between oppositely charged ions?
- Covalent bond
- Metallic bond
- Ionic bond (Correct answer)
- Hydrogen bond
Correct answer: Ionic bond
An ionic bond forms when one atom donates an electron to another, creating oppositely charged ions that attract each other.
Question 3: According to the law of conservation of mass, what is true about a chemical reaction?
- Mass is created from energy
- The total mass of reactants equals the total mass of products (Correct answer)
- Mass is destroyed in exothermic reactions
- Products always have greater mass than reactants
Correct answer: The total mass of reactants equals the total mass of products
The law of conservation of mass states that matter is neither created nor destroyed in a chemical reaction, so the total mass of reactants equals the total mass of products.
Question 4: What is the pH of a neutral solution at 25°C?
- 0
- 7 (Correct answer)
- 14
- 1
Correct answer: 7
At 25°C, a neutral solution has equal concentrations of H⁺ and OH⁻ ions, resulting in a pH of exactly 7.
Question 5: Which subatomic particle has a negative charge and is found outside the nucleus?
- Proton
- Neutron
- Electron (Correct answer)
- Positron
Correct answer: Electron
Electrons carry a negative charge of −1 and orbit the nucleus of an atom in electron shells or orbitals.
Question 6: What does the mole concept represent in chemistry?
- The mass of one atom in grams
- 6.022 × 10²³ particles of a substance (Correct answer)
- The volume of a gas at STP
- The number of neutrons in an element
Correct answer: 6.022 × 10²³ particles of a substance
One mole is defined as 6.022 × 10²³ (Avogadro's number) of particles (atoms, molecules, or ions) of a substance.
AS Associate Of Science In Chemistry 1
What is the number of protons in an atom called?