Q And A For Any Subject Any Class Exam

Here is a list of 3 probable questions for the Senior Secondary Chemistry exam, along with detailed answers: ________________________________________ Question 1: Explain the structure of the atom according to Bohr’s model. How does it differ from Rutherford’s model? Answer: Bohr’s model of the atom is based on the quantum theory that energy is transferred only in certain well-defined quantities. Electrons move in orbits of fixed size and energy around the nucleus. The energy of the electron depends on the size of the orbit, with smaller orbits corresponding to lower energy levels. A key feature of Bohr's model is that electrons can only occupy specific orbits (energy levels) and can jump from one orbit to another by emitting or absorbing energy in the form of light (photons). In contrast, Rutherford’s model of the atom depicted electrons moving around the nucleus in a manner similar to planets orbiting the sun. However, this model did not explain why the negatively charged electrons do not spiral into the positively charged nucleus, which would be expected due to the forces of attraction. Bohr’s model improved upon this by introducing the concept of quantized energy levels that prevent such a collapse. ________________________________________ Question 2: What are oxidation and reduction reactions? Explain with examples. Answer: Oxidation is the process in which a substance loses electrons, while reduction is the process in which a substance gains electrons. In any redox (oxidation-reduction) reaction, both oxidation and reduction occur simultaneously. Oxidation and reduction are often explained in terms of the transfer of oxygen or hydrogen atoms, but the most fundamental explanation involves the transfer of electrons. For example, in the reaction between zinc and copper sulfate: Zn(s) +CuSO4(aq)→ZnSO4(aq)+Cu(s). Zinc is oxidized because it loses electrons and becomes Zn²⁺: Zn→Zn2++2e− Copper is reduced because it gains electrons and is deposited as Cu: Cu2++2e−→Cu. This is a typical redox reaction where one substance is oxidized (zinc) and another is reduced (copper ions). ________________________________________ Question 3: Describe the concept of hybridization in chemistry. What is the hybridization of carbon in methane (CH₄)? Answer: Hybridization is the concept of mixing atomic orbitals to form new hybrid orbitals that are suitable for the pairing of electrons to form chemical bonds. It explains the shape and bond angles in molecules that cannot be described by traditional atomic orbitals. There are several types of hybridization such as sp, sp², sp³, etc., which correspond to the different ways in which atomic orbitals combine. In methane (CH₄), the carbon atom undergoes sp³ hybridization. The carbon atom's one s orbital and three p orbitals hybridize to form four equivalent sp³ hybrid orbitals. These orbitals then overlap with the 1s orbitals of hydrogen atoms to form four sigma (σ) bonds, resulting in a tetrahedral structure with bond angles of approximately 109.5°. This sp³ hybridization explains the symmetrical shape and bond properties of methane. ________________________________________ These questions provide a balanced level of difficulty, addressing fundamental concepts in Chemistry while giving students a clear and structured understanding of key topics.