Chemistry Basics: Important Concepts and Questions with Answers, Cheat Sheet of Chemistry

Download Chemistry Basics: Important Concepts and Questions with Answers and more Cheat Sheet Chemistry in PDF only on Docsity! SOME BASIC CONCEPTS OF CHEMISTRY IMPORTANT QUESTIONS AND THEIR ANSWERS LEVEL 1 QUESTIONS (Easy) 1. Define the term 'Mole' in chemistry. Answer: The mole is the SI unit of measurement used to express the amount of a substance. One mole of a substance contains Avogadro's number of entities, which is approximately 6.022 x 10^23. 2. Explain the difference between molecular mass and molar mass. Answer: Molecular mass is the sum of the atomic masses of all the atoms in a molecule, while molar mass is the mass of one mole of a substance. Molar mass is expressed in g/mol and is numerically equal to the molecular mass but has units. 3. How do you calculate the number of moles in a given mass of a substance? Answer: The number of moles (n) can be calculated using the formula: n = (Given mass in grams) / (Molar mass in g/mol). 4. Define empirical formula and molecular formula. Answer: The empirical formula represents the simplest whole-number ratio of different atoms in a compound. The molecular formula represents the actual number of atoms of each element in a molecule. 5. What is Avogadro's law? Answer: Avogadro's law states that equal volumes of gases, at the same temperature and pressure, contain an equal number of molecules. This implies that the ratio of volumes of gases in a chemical reaction corresponds to the ratio of small whole numbers. 6. Explain the concept of limiting reactant in a chemical reaction. Answer: The limiting reactant is the reactant that is completely consumed in a chemical reaction, limiting the amount of product that can be formed. The other reactant is called the excess reactant, as there is more of it than required for the reaction. 7. How does concentration differ from density in chemistry? Answer: Concentration refers to the amount of solute present in a given amount of solution, expressed as moles per unit volume (e.g., mol/L). Density, on the other hand, is the mass per unit volume of a substance, typically expressed in g/cm³ or kg/m³. 8. Explain the concept of empirical and molecular formulas with an example. Answer: The empirical formula represents the simplest whole-number ratio of elements in a compound. The molecular formula gives the actual number of each type of atom in a molecule. For example, the empirical formula of hydrogen peroxide is HO, while its molecular formula is H2O2. LEVEL 2 QUESTIONS (Intermediate) 1. Define the term 'Atomic Mass Unit' (AMU). Answer: Atomic Mass Unit (AMU) is a unit of mass used to express atomic and molecular weights. It is defined as one twelfth of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and it is approximately equal to 1.66 x 10^-27 kg. 2. Explain the difference between empirical formula and molecular formula with an example. Answer: The empirical formula shows the simplest whole-number ratio of different atoms in a compound, while the molecular formula gives the actual number of each type of atom in a molecule. For example, the empirical formula of glucose is CH2O, while its molecular formula is C6H12O6. 3. Calculate the molecular mass of water (H2O) using the atomic masses: H = 1 g/mol, O = 16 g/mol. Answer: Molecular mass = (2 × atomic mass of H) + atomic mass of O Molecular mass = (2 × 1 g/mol) + 16 g/mol = 18 g/mol 4. State Dalton's Atomic Theory. Answer: Dalton's Atomic Theory states that: - All matter is composed of indivisible particles called atoms. - Atoms of the same element are identical in size, mass, and chemical properties. - Atoms of different elements have different properties. - Atoms combine in simple, whole-number ratios to form compounds. - In chemical reactions, atoms are rearranged, separated, or combined.