Acids and Alkalis

• Methyl orange is an acid-base indicator that is red in acidic solutions and yellow in basic solutions.
• Neutral substances have pH values equal to 7
• Alkaline solutions have pH values greater than 7
• The strength of an acid or base depends on the proportion of H+ or OH- ions produced in solution.
• Acidic solutions have pH values less than 7
• Acids turn blue litmus paper red, while alkalis turn red litmus paper blue.
• Litmus paper is a common acid-base indicator that turns red in the presence of an acid and blue in the presence of a base.
• Phenolphthalein is an acid-base indicator that is colorless in acidic solutions but turns pink to red in alkaline solutions.
• Acidic substances have pH values less than 7
• Basic (alkaline) substances have pH values greater than 7
• The pH scale ranges from 0 to 14, with 0 being the most acidic and 14 being the most alkaline
• The pH scale measures the concentration of hydrogen ions (H+) in a solution, with lower numbers indicating higher concentrations of H+ and more acidic conditions.
• A pH value of 0 indicates a very strong acid, while a pH value of 14 indicates a very strong base or alkali.
• Acid + Metal → Salt + Hydrogen Gas
• Metal + Water → Salt + Hydrogen Gas
• Strong acids are completely ionized, while weak acids only partially dissociate into hydrogen ions (H+) and their conjugate bases.
• Weak acids can be neutralised by strong alkali but not by other weak acids.
• A strong acid completely dissociates into hydrogen ions (H+) and its conjugate base when it's added to water.
• Weak acids only partially dissociate into hydrogen ions (H+) and their conjugate bases when they are added to water.
• A universal indicator can be used as it changes color from yellow (acid) through orange, green, purple, pink, and finally red (alkali).
• A buffer solution resists changes in its pH when small amounts of acid or alkali are added.
• Universal Indicator is a mixture of indicators with different colors at different pH levels, allowing for more precise measurement of pH.
• Another method to test whether a substance is acidic or basic involves adding a few drops of phenolphthalein into the solution. If the solution is neutral, no change will occur; if the solution is acidic, there will be no color change; but if the solution is basic, the solution will turn bright pink.
• A titration curve shows how the concentration of hydrogen ions changes as an acid reacts with a base.
• Strong acids include sulfuric acid (H2SO4), nitric acid (HNO3), hydrochloric acid (HCl), phosphoric acid (H3PO4), carbonic acid (H2CO3), and perchloric acid (HCIO4).
• Alkaline substances have pH values greater than 7
• Most living organisms function best at neutral pH levels between 6.5 and 8.5.
• Base + Acid → Salt + Water
• pH levels are important because they affect various biological processes such as enzyme activity, cellular respiration, and protein function
• Neutralization is when an acid reacts with a base to form salt and water.
• Salt + Acid → Salt + Water
• Strong acids are completely ionized in aqueous solutions, meaning they dissociate into their component ions.
• Changes in pH can affect enzyme activity, cell membrane permeability, protein structure, and other biological processes.
• The strength of an acid is determined by the extent to which it releases hydrogen ions (H+).