1.12 Acids and bases

• Bronsted-Lowry acids are proton donors, and when mixed with water, hydrogen ions are released, forming hydronium ions, also known as hydronium ions, which are H3O+.
• Bronsted-Lowry bases are proton acceptors, and when a base reacts with an acid, a hydronium ion is formed.
• Diprotic acids like sulfuric acid produce two H+ ions for every acid molecule, so the concentration of the acid is two times the concentration of H+ ions.
• The pH of a strong acid is calculated by assuming that strong acids dissociate fully and the concentration of H+ ions is equal to the concentration of the acid.
• When calculating the pH of a strong base, it is assumed that the base dissociates fully to form OH- ions, and the concentration of the base equals the concentration of OH- ions.
• To calculate the pH of a base, the concentration of H+ ions is needed, which can be found using the ionic product of water expression, KW.
• For monoprotic acids like hydrochloric acid and nitric acid, the concentration of H+ ions is equal to the concentration of the acid.
• Bronsted-Lowry acid-base equilibria is a concept in chemistry that explains how acids and bases work.
• The buffer is made up of 0.1 moles of ethanoic acid, 0.1 moles of methanoic acid, and 0.1 moles of NaOH.
• Calculations involve adding a small amount of an acid or base to a buffer and determining the change in pH.
• When 10 centimeters cubed of one mole dilute hydrochloric acid is added to a decimetres cubed of buffer solution, the pH changes from 7 to 6.
• The usual assumptions are used in calculations.
• The change in pH is due to the buffer resisting the change.
• When a base is added to a buffer, the hydroxide ions react with the H+ ions, shifting equilibrium to the right.
• The minus log of H+ can be taken in the Ka expression.
• A buffer is a system where two equilibrium equations exist in the same beaker.
• An acidic buffer resists the change in pH in order to keep the solution below pH 7 and is made from a weak acid and its salt.
• When an acid is added to a buffer, the H+ ions react with the athan iodine, shifting equilibrium to the left.
• Salts associate and dissociate fully, meaning equilibrium is well to the right in a buffer.
• An acidic buffer is made from a weak acid and its salt.
• A buffer is made by using a weak acid and its salt, and must be the salt of the acid that is being used.
• In a buffer solution, there are two equilibrium equations at play.
• There are two types of buffer: acidic and basic.
• The definition and determination of pH is a crucial aspect of AQA acids and bases.
• The half neutralization point is the point halfway between zero and the equivalence point, which can be used to calculate the pKa of a weak acid.
• The pH change in a titration can also go the other way around, starting with a strong base and adding an acid.
• The Ka expression equals the concentration of H+.
• The Ka expression can be simplified by cancelling out the concentration of H+ and the concentration of A-.
• The Ka expression can be rewritten as the concentration of H+ times the concentration of A-.
• In a titration, the pH change is sharpest when a strong acid and a strong base are used.
• The concentration of H+ in a titration is equal to the concentration of A-.
• The pH change from H+ ions reacting in full is smallest when a weak acid and a weak base are used in a titration.
• The method when nearing the end point is critical, and measurements need to be made from the bottom of the meniscus.
• The classic shape of a titration curve is an S-shaped curve.
• Titration curves show pH against volume of base added from a titration, with different combinations of weak acids, strong acids, strong bases, and weak bases.
• The titration curve starts at pH one when using a strong acid, and rises quickly to a certain point and then becomes basic.
• Results need to be recorded to two decimal places and repeated until they are within 0.1 centimeters cubed of each other.
• When a strong base is used, the titration curve starts at pH water and rises to a certain point, then becomes basic.
• The equivalence point or end point is the point where the acid has been neutralized fully by the base, marked by a sharp vertical rise on the titration curve.
• When a weak acid is used, the titration curve starts higher up the curve and doesn't rise as much because a weak base has been used.