# [Answer] What does “acid” indicate?

###### Answer: hydrogen ion is present
What does “acid” indicate?

Reactions of acids are often generalized in the form HA ⇌ H + A where HA represents the acid and A is the conjugate base. This reaction is referred to as protolysis. The protonated form (HA) of an acid is also sometimes referred to as the free acid. Acid-base conjugate pairs differ by one proton and can be interconverted by the addition or removal of a proton (protonation and deprotonation respectively). Note that the acid can be the charged species and the conjugate base can be neutral in which case the generalized reaction scheme could be wri…

Reactions of acids are often generalized in the form HA ⇌ H + A where HA represents the acid and A is the conjugate base. This reaction is referred to as protolysis. The protonated form (HA) of an acid is also sometimes referred to as the free acid. Acid-base conjugate pairs differ by one proton and can be interconverted by the addition or removal of a proton (protonation and deprotonation respectively). Note that the acid can be the charged species and the conjugate base can be neutral in which case the generalized reaction scheme could be written as HA ⇌ H + A. In solution there exists an equilibrium between the acid and its conjugate base. The equilibrium constant K is an expression of the equilibrium concentrations of the molecules or the ions in solution. Brackets indicate concentration such that [H2O] means the concentration of H2O. The acid dissociation constant Ka is generally used in the context of acid-base reactions. The numerical value of Ka is equal to the product of the concentrations of the products divided by the concentration of the reactants where the reactant is the acid (HA) and the products are the conjugate base and H . The stronger of two acids will have a higher Ka than the weaker acid; the ratio of hydrogen ions to acid will be higher for the stronger acid as the stronger acid has a greater tendency to lose its proton. Because the range of possible values for Ka spans many orders of magnitude a more manageable constant pKa is more frequently used where pKa = −log10 Ka. Stronger acids have a smaller pKa than weaker acids. Experimentally determined pKa at 25 °C in aqueous solution are often quoted in textbooks and reference material.

Acid value (or neutralization number or acid number or acidity) is the mass of potassium hydroxide (KOH) in milligrams that is required to neutralize one gram of chemical substance. The acid number is a measure of the number of carboxylic acid groups in a chemical compound such as a fatty acid or in a mixture of compounds. In a typical procedure a known amount of sample dissolved in an organic solvent (often isopropanol) and titrated with a solution of potassium hydroxide (KOH) of known concentration using phenolphthalein as a colour indicator.

Acid value (or neutralization number or acid number or acidity) is the mass of potassium hydroxide (KOH) in milligrams that is required to neutralize one gram of chemical substance. The acid number is a measure of the number of carboxylic acid groups in a chemical compound such as a fatty acid or in a mixture of compounds. In a typical procedure a known amount of sample dissolved in an organic solvent (often isopropanol) and titrated with a solution of potassium hydroxide (KOH) of known concentration using phenolphthalein as a colour indicator. The acid number is used to quantify the acidity of a substance e.g. biodiesel. It is the quantity of base expressed in milligrams of potassium hydroxide that is required to neutralize the acidic constituents in 1 g of sample. ${\displaystyle AN=(V_{eq}-b_{eq})N{\frac {56.1\ g\ mol^{-1}}{W_{oil}}}}$ Veq is the volume of titrant (ml) consumed by the crude oil sample and 1 ml of spiking solution at the equivalent point beq is the…