Pump up your pH knowledge with our quiz on acidity and basicity measurement!

pH: A Measure of Acidity or Basicity of Aqueous Solutions

• pH is a scale used to specify the acidity or basicity of an aqueous solution.

• The pH scale is logarithmic and inversely indicates the activity of hydrogen ions in the solution.

• Acidic solutions have lower pH values than basic or alkaline solutions.

• Solutions with a pH less than 7 are acidic, solutions with a pH greater than 7 are basic, and solutions with a pH of 7 are neutral.

• The pH value can be less than 0 for very concentrated strong acids or greater than 14 for very concentrated strong bases.

• The pH scale is traceable to a set of standard solutions whose pH is established by international agreement.

• pH values can be measured with a glass electrode and a pH meter or a color-changing indicator.

• The first electronic method for measuring pH was invented by Arnold Orville Beckman in 1934.

• pH is defined as the decimal logarithm of the reciprocal of the hydrogen ion activity, aH+.

• The pH scale ranges from 0 to 14, with a pH of 7 indicating neutrality, values less than 7 indicating acidity, and values greater than 7 indicating basicity.

• pH can be measured using indicators, which change color depending on the pH of the solution they are in.

• pH values can be measured in non-aqueous solutions, but they are based on a different scale from aqueous pH values.pH Scale: Definition, Applications, and Calculations

• The pH scale is a measure of acidity or basicity of an aqueous solution.

• The pH scale ranges from 0 to 14, with 7 being neutral.

• The unified absolute pH scale is a new approach to measuring pH, based on the absolute chemical potential of the proton.

• The measurement of pH can become difficult at extremely acidic or alkaline conditions, such as below pH 2.5 or above pH 10.5.

• In living organisms, the pH of various body fluids, cellular compartments, and organs is tightly regulated to maintain a state of acid-base balance known as acid–base homeostasis.

• The pH of seawater is typically limited to a range between 7.4 and 8.5, and there is evidence of ongoing ocean acidification caused by carbon dioxide emissions.

• Strong acids and bases are compounds that are essentially fully dissociated in water.

• Weak acids and bases can be treated using the formalism of acid dissociation constant.

• Water itself is a weak acid and a weak base and must be taken into account at high pH and low solute concentration.

• The pH of a solution is defined as the negative logarithm of the concentration of H+, and the pOH is defined as the negative logarithm of the concentration of OH-.

• When calculating the pH of a solution containing acids and/or bases, a chemical speciation calculation is used to determine the concentration of all chemical species present in the solution.

• The United States Department of Agriculture Natural Resources Conservation Service classifies soil pH ranges based on soil parent material, erosional effects, climate, and vegetation.Calculating pH Using Equilibrium Constants

• The pH of a solution can be calculated using equilibrium constants.

• The concentration of hydrogen ions (H+) can be calculated using the ionization constant (Kw) of water, which is 10^-14 M^2 at 25°C.

• The general method for calculating pH involves writing mass-balance equations for each reagent in the system, which includes equilibrium constants.

• There are three non-linear simultaneous equations in the three unknowns [A], [B], and [H], which can be solved using computer programs.

• This method is applicable to systems with multiple reagents or when many complexes are formed.

• Polyprotic acids are also amenable to spreadsheet calculations.

• Stability constants are defined as a quotient of concentrations, not activities.

• Activities are used when more complicated expressions are required.

• The calculation of hydrogen ion concentrations is a key element in determining equilibrium constants by potentiometric titration.

• The concentration of hydroxide ions (OH-) can also be calculated using the ionization constant of water.

• The pH of a solution can be used to calculate the concentration of many other species in the solution.

• Computer programs are available to perform these calculations.