Chemistry 1st Ch 04 Chemical Changes

Chemistry - First Paper Chapter 4: Chemical Changes Selected Questions and Answers (HSC English Version) 0.1 Chapter 4: Chemical Changes Group A: Knowledge Based Questions [At a Glance] (1) Chemical Reaction and Green Chemistry: 1. What is green chemistry? [Di. B. 2016, 2017; J. B. 2016; C. B. 2017] Answer: Green chemistry is the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances. 2. What is atom economy? [J. B. 2017] Answer: Atom economy is a measure of the proportion of reactant atoms that become part of the desired product in a chemical reaction. 3. What is greener method? Answer: A greener method is a chemical process that minimizes waste, uses non-toxic reagents, operates under mild conditions, and maximizes atom economy. 4. Write formula of maleic anhydride. Answer: The chemical formula of maleic anhydride is C4H2O3. 5. What is irreversible reaction? Answer: A chemical reaction that proceeds in only one direction (forward) and goes to comple- tion is called an irreversible reaction. 6. What is reversible reaction? Answer: A reaction that can proceed in both forward and backward directions simultaneously under the

Answer: A promoter is a substance that is not a catalyst itself but increases the activity of a catalyst when added to the reaction mixture. 7. What is enzyme? [Syl. B. 2017; Ctg. B. 2015] Answer: Enzymes are complex nitrogenous organic compounds (proteins) produced by living plants and animals that act as biological catalysts. (3) Chemical Equilibrium: 1. What is chemical equilibrium? [C. B. 2017; R. B. 2017; Di. B. 2016] Answer: Chemical equilibrium is the state of a reversible reaction where the rates of the forward and backward reactions are exactly equal. 2. What is Le–Chatelier principle? [B. B. 2016; R. B. 2015] Answer: If a system at equilibrium is subjected to a change in temperature, pressure, or concentration, the equilibrium will shift to counteract the effect of the change. 3. What is reaction quotient (Qc)? Answer: Reaction quotient is the ratio of the product of concentrations of products to reactants at any given moment, not necessarily at equilibrium. 4. What is equilibrium constant (Kc)? [Syl. B. 2015] Answer: It is the ratio of the product of equilibrium concentrations of products to reactants, each raised to the power of their stoichiometric coefficients. 5. Wha

Answer: The species formed after a base accepts a proton (H+) is called its conjugate acid. (5) pH of a Solution, Buffer Solution: 1. What is pH of a solution? [D. B. 2017; R. B. 2017; J. B. 2016] Answer: pH is the negative logarithm to the base 10 of the hydrogen ion concentration in mol/L. (pH = −log[H+]). 2. What is buffer solution? [Ctg. B. 2016; Syl. B. 2016; B. B. 2016] Answer: A solution whose pH does not change significantly upon the addition of a small amount of strong acid or strong base. 3. Give example of acidic buffer solution. Answer: A mixture of weak acetic acid (CH3COOH) and its salt sodium acetate (CH3COONa). 4. Give example of basic buffer solution. Answer: A mixture of weak base ammonium hydroxide (NH4OH) and its salt ammonium chloride (NH4Cl). 5. What is Henderson’s equation for acidic buffer soln? Answer: pH = pKa + log [Salt] [Acid]. 6. What is ETP? Answer: ETP stands for Effluent Treatment Plant, a facility designed to purify industrial wastewater before its safe disposal. (6) Law of Conservation of Mass & Energy: 1. What is enthalpy? [Syl. B. 2019] Answer: Enthalpy (H) is the total heat content of a system at constant pressure, equal to internal energy plus