1. What is the fundamental unit of matter?
Answer: Atom.
2. Define Dalton’s atomic theory.
Answer: Dalton’s atomic theory states that all matter is composed of tiny, indivisible particles called atoms, which cannot be created or destroyed in a chemical reaction.
3. Differentiate between an atom and a molecule.
Answer: An atom is the smallest unit of an element that retains its chemical properties, while a molecule is a combination of two or more atoms bonded together.
4. Explain the concept of an element.
Answer: An element is a pure substance composed of only one type of atom, characterized by its unique atomic number.
5. Define a compound.
Answer: A compound is a substance composed of two or more different elements chemically bonded in a fixed ratio.
6. What are the laws of chemical combination? Name them.
Answer: The laws of chemical combination are the Law of Conservation of Mass, the Law of Definite Proportions, and the Law of Multiple Proportions.
7. What is meant by the Law of Conservation of Mass?
Answer: The Law of Conservation of Mass states that in a chemical reaction, mass is neither created nor destroyed. The total mass of the products equals the total mass of the reactants.
8. Define atomic mass and molecular mass.
Answer: Atomic mass is the mass of an atom of an element relative to the mass of a carbon-12 atom, which is assigned a mass of 12 atomic mass units (u). Molecular mass is the sum of the atomic masses of the atoms in a molecule.
9. Explain the concept of the mole.
Answer: The mole is a unit used in chemistry to express amounts of a substance. One mole of any substance contains Avogadro’s number (6.022 × 10^23) of particles.
10. What is molar mass?
Answer: Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol).
11. How do you calculate the percentage composition of a compound?
Answer: Percentage composition of a compound can be calculated by dividing the mass of each element in the compound by the molar mass of the compound, then multiplying by 100%.
12. Define empirical formula.
Answer: The empirical formula of a compound represents the simplest whole-number ratio of atoms of each element present in the compound.
13. What is a molecular formula?
Answer: The molecular formula of a compound represents the actual number of atoms of each element in a molecule of the compound.
14. How do you determine the empirical formula from the percentage composition?
Answer: To determine the empirical formula from the percentage composition, divide the percentage of each element by its atomic mass, then divide the results by the smallest value obtained. The resulting ratios represent the subscripts in the empirical formula.
15. What is stoichiometry?
Answer: Stoichiometry is the branch of chemistry that deals with the quantitative relationships between reactants and products in chemical reactions.
16. Explain the term “chemical equation.”
Answer: A chemical equation is a symbolic representation of a chemical reaction, showing the reactants on the left side and the products on the right side, with coefficients indicating the relative amounts of each substance involved.
17. What is the law of conservation of mass applied to chemical equations?
Answer: The law of conservation of mass states that the total mass of the reactants must equal the total mass of the products in a chemical reaction. This principle is represented by balancing chemical equations.
18. How do you balance a chemical equation?
Answer: To balance a chemical equation, adjust the coefficients of the reactants and products so that the number of atoms of each element is the same on both sides of the equation.
19. What is a limiting reagent?
Answer: A limiting reagent is the reactant that is completely consumed in a chemical reaction, limiting the amount of product that can be formed.
20. Define theoretical yield and actual yield.
Answer: The theoretical yield is the maximum amount of product that can be obtained in a chemical reaction based on the stoichiometry of the reaction. The actual yield is the amount of product obtained experimentally, which may be less than the theoretical yield due to factors such as incomplete reactions or side reactions.