Acid Properties Essay

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OBJECTIVE The purpose of this experiment is to study the properties of acidic/basic substances using indicators and a pH meter. INTRODUCTION Acids and bases are important classes of chemical compounds that have many uses in science. The commonly accepted modern definition of acids and bases is the Bronsted-Lowry definition which, “Acids are substances which donate protons (H+ ions), and bases are substances that can accept protons”. Using this definition, the acidity or basicity of a substance is defined to be the relative tendency of that substance to donate or accept protons. While pH is a measure of the acidity or basicity of a substance. It’s mathematically defined as -log10[H+],[H+] denotes the concentration of the proton in the solution. A pH of 7 is considered to be neutral (pure water). Any substance which gives more protons than pure water will have a pH less than 7 and is considered to be acidic. Similarly, a substance with a pH lower than 7 is basic.Besides, indicators are substances which help us distinguish between acids and bases. Typically, this is achieved by a change of colour corresponding to a change in the pH of the substance. This property is called halochromaticity.Generally indicators are weak acids or bases (substances with a pH around 7). Small quantities of the solution whose acidity or basicity we need to determine, are added to the indicator. Good indicators undergo a sharp color change at a particular pH value, which helps us determine the pH of the uknown solution.The mechanism by which indicators react in water can be exxplained as follows: Indicator + H2O ↔ Hydronium ion + Conjugate base of indicator By the concepts of equilibrium, we know that the acid constant is defined as : Ka = [H+][conjugate base]/[acid] We subsequently write the following equation, which is derived from the definition of

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