11th Quarterly Question Paper Chemistry 2019

The chemistry question paper for the 11th quarterly exam of 2019 focuses on various fundamental concepts and principles. It helps students understand topics like atomic structure, bonding, thermodynamics, and chemical reactions. The questions and answers provided are designed to support effective learning and preparation for exams.

11th Quarterly Question Paper Chemistry 2019

Question: What is the atomic number of an element?

Answer: The atomic number of an element is the number of protons in the nucleus of an atom, which also determines the element’s position in the periodic table.

Question: Define isotopes with examples.

Answer: Isotopes are atoms of the same element with the same atomic number but different mass numbers. Examples include Carbon-12 and Carbon-14.

Question: What is the law of conservation of mass?

Answer: The law of conservation of mass states that mass is neither created nor destroyed during a chemical reaction.

Question: Explain the octet rule in chemical bonding.

Answer: The octet rule states that atoms tend to form bonds to have eight electrons in their outermost shell, achieving a stable electronic configuration.

Question: What are covalent bonds?

Answer: Covalent bonds are chemical bonds formed by the sharing of electrons between two atoms to achieve stability.

Question: State the first law of thermodynamics.

Answer: The first law of thermodynamics states that energy can neither be created nor destroyed; it can only be transformed from one form to another.

Question: What is the difference between an endothermic and an exothermic reaction?

Answer: Endothermic reactions absorb heat from the surroundings, while exothermic reactions release heat to the surroundings.

Question: Define molarity and provide its formula.

Answer: Molarity is the number of moles of solute dissolved in one liter of solution. The formula is M = moles of solute/volume of solution in liters.

Question: What is the pH scale?

Answer: The pH scale measures the acidity or basicity of a solution, ranging from 0 (acidic) to 14 (basic), with 7 being neutral.

Question: Explain Le Chatelier’s Principle.

Answer: Le Chatelier’s Principle states that if a system in equilibrium is subjected to a change, the system adjusts itself to counteract the change and restore equilibrium.

Question: What are electrolytes?

Answer: Electrolytes are substances that dissociate into ions in a solution, conducting electricity.

Question: Define electrolysis and give an example.

Answer: Electrolysis is the chemical decomposition of a substance by passing an electric current through it. Example: Electrolysis of water.

Question: What is a redox reaction?

Answer: A redox reaction involves the simultaneous oxidation (loss of electrons) and reduction (gain of electrons) of substances.

Question: Explain the Aufbau principle in electron configuration.

Answer: The Aufbau principle states that electrons occupy orbitals of lower energy first before filling higher energy orbitals.

Question: What is the periodic law?

Answer: The periodic law states that the properties of elements are periodic functions of their atomic numbers.

Question: Differentiate between ionic and covalent compounds.

Answer: Ionic compounds are formed by the transfer of electrons, while covalent compounds are formed by the sharing of electrons.

Question: What are catalysts?

Answer: Catalysts are substances that increase the rate of a chemical reaction without undergoing permanent changes themselves.

Question: Define hybridization and give an example.

Answer: Hybridization is the mixing of atomic orbitals to form new hybrid orbitals of equal energy. Example: sp3 hybridization in methane (CH4).

Question: What are acids and bases according to the Arrhenius theory?

Answer: According to Arrhenius theory, acids produce H+ ions in aqueous solutions, while bases produce OH− ions.

Question: Describe the structure of benzene.

Answer: Benzene has a cyclic structure with six carbon atoms arranged in a hexagon, each bonded to one hydrogen atom, and alternating double bonds.

Question: What is the difference between a molecular and an empirical formula?

Answer: A molecular formula represents the actual number of atoms in a molecule, while an empirical formula shows the simplest whole-number ratio of atoms.

Question: Define surface tension and its importance.

Answer: Surface tension is the tendency of liquid surfaces to shrink into the minimum surface area, important in processes like capillary action.

Question: What are allotropes?

Answer: Allotropes are different forms of the same element with different physical and chemical properties, like diamond and graphite for carbon.

Question: State the difference between homogeneous and heterogeneous mixtures.

Answer: Homogeneous mixtures have a uniform composition, while heterogeneous mixtures have distinct phases or parts.

Question: What are transition elements?

Answer: Transition elements are d-block elements that form colored compounds and exhibit variable oxidation states.

Question: Explain the concept of atomic radius.

Answer: Atomic radius is the distance from the nucleus to the outermost electron shell of an atom.

Question: What is meant by equilibrium in a chemical reaction?

Answer: Equilibrium in a chemical reaction is a state where the rates of the forward and reverse reactions are equal, resulting in no net change.

Question: What is Avogadro’s number?

Answer: Avogadro’s number is 6.022 × 10^23, representing the number of particles in one mole of a substance.

Question: What are isomers?

Answer: Isomers are compounds with the same molecular formula but different structural arrangements of atoms.