1. Which of the following is NOT a physical property?
Answer:
Explanation:
Reactivity with acid is a chemical property, not a physical one.
2. The SI unit of mass is:
Answer:
Explanation:
The International System of Units (SI) recognizes the kilogram as the base unit of mass.
3. The number of atoms in one mole of carbon is known as:
Answer:
Explanation:
Avogadro's number (6.022 x 10^23) represents the number of atoms in one mole of any substance.
4. What does the term "molar mass" refer to?
Answer:
Explanation:
Molar mass is the mass (in grams) of one mole of a substance.
5. Which of the following represents a chemical change?
Answer:
Explanation:
Rusting is a process wherein iron reacts with moisture and oxygen, leading to a chemical change.
6. How many significant figures are in the number 0.002305?
Answer:
Explanation:
Leading zeros are not counted as significant. The significant figures are 2305.
7. What is the empirical formula of a compound that has 40% carbon, 6.7% hydrogen, and 53.3% oxygen by weight?
Answer:
Explanation:
Empirical formula represents the simplest whole-number ratio of the elements in a compound.
8. The atomic number of an element represents:
Answer:
Explanation:
Atomic number is the number of protons present in the nucleus of an atom.
9. Which of the following is an extensive property?
Answer:
Explanation:
Extensive properties depend on the amount of substance present.
10. Isotopes of an element differ in the number of:
Answer:
Explanation:
Isotopes of an element have the same number of protons but different numbers of neutrons.
11. The law that states that matter can neither be created nor destroyed is:
Answer:
Explanation:
This law asserts that the total mass remains constant before and after a chemical reaction.
12. If an element X has two isotopes with atomic masses 35 and 37, and their relative abundance is 3:1, the average atomic mass of X is:
Answer:
Explanation:
Average atomic mass = (35*3 + 37*1) / 4 = 142/4 = 35.5
13. The mass percent of an element in a compound is defined as:
Answer:
Explanation:
Mass percent gives the percentage by mass of each element in a compound.
14. How many moles are in 22 grams of carbon dioxide (CO2)?
Answer:
Explanation:
Molar mass of CO2 = 44g/mol. So, 22 grams of CO2 = 22/44 = 0.5 moles.
15. Which of the following is a homogeneous mixture?
Answer:
Explanation:
A homogeneous mixture has a uniform composition throughout.
16. The atomic mass of an element is determined relative to the mass of:
Answer:
Explanation:
Carbon-12 is taken as the standard reference for determining atomic masses.
17. The volume occupied by one mole of a gas at STP is:
Answer:
Explanation:
At standard temperature and pressure (STP), one mole of any gas occupies 22.4 liters.
18. A solution with a pH of 7 is:
Answer:
Explanation:
A pH value of 7 indicates a neutral solution.
19. Which of the following is a scalar quantity?
Answer:
Explanation:
Scalar quantities have magnitude but no direction.
20. Which postulate of Dalton's atomic theory has been modified?
Answer:
Explanation:
With the discovery of subatomic particles, it's now known that atoms can be divided into protons, neutrons, and electrons.