A reaction between an acid and a base will yield salt and water.
This kind of reaction is referred to as a neutralization reaction.
Amphirotic: Water is amphiprotic meaning that it can both accept and donate protons, which we know to be true due to the presence of OH- and H30+ ions.
Autoprotolysis reaction: Auto refers to self, lysis refers to splitting, so H20--->H30+ + OH- It means a proton transfer occurring between the same type of molecule.
From this RXN of autoprotolysis, we actually get the equilibrium constant Kc = P (as water is not included). What's more however is that Kc is actually equal to Kw.
Kw is just the autoprotolysis constant of water, and at 25 degrees Celsius, the autoprotolysis constant is water is equal to 1.0 *10^-14.
In an acidic solution, the hydronium concentration will be greater than the concentration of hydride, and the opposite is true for a basic, or alkaline solution.
A pH of 14 is very alkaline or basic, whereas a pH of one is very acidic. A pH of 7 is considered neutral.
Remember, pH is set on a log scale! So, if you are comparing a solution with a pH of 5 versus a pH of 6, the solution with a pH of 5 is TEN TIMES more acidic than the solution with a pH of 6. This distinction is very important to biological systems given their general sensitivity to pH when it comes to the function of proteins, as well as other impacts.
pKw=14, so pH + pOH=14
When calculating the equilibrium constants of acids and bases, you will only calculate them for WEAK acids and bases because otherwise, the Ka or Kb value will be very large! Also, the reactants at equilibrium will likely equal zero due to the fact that the strong acids and bases completely dissociate in the solution. These values are the acidity and base constants. They may also be called ionization, or dissociation constants.
Acidity and basicity constants are often given as their negative log, known as their pKa, or pKb values. Do not get confused! pH is different from these values!
The proton donating strength of an acid is measured by its acidity constant Ka.
The proton accepting strength is measured by its basicity constant Kb.
The smaller the Kb or Ka constant, the weaker the acid or the base. The larger the pKa or pKb values, the weaker the strength of the acid or the base.
This is different from pH because for an acid, the lower the pH value, the higher its strength, and the lower the pKa value, the higher its strength! HOWEVER, for a base, the closer the pH is to 14, the higher the strength of the base, whereas for a base, the higher its pKb value, the weaker the base is! I did not realize this for a while, so just make sure that you understand that for an acid, pH and pKa can be interpreted in the same way. However, for a base, the pKb value and the pH value are opposite. remember too that 'p' means inverse log, so pH is a measure of H+ concentration in solution, whereas pKa is the inverse log of the acidity constant, and pKb is the inverse log of the basicity constant.
pH pOH pKa pKb review of topics
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Re: pH pOH pKa pKb review of topics
Postby Chem_Mod » Mon Jan 30, 2023 10:11 pm
Yes, this is all correct! Great job. ☻
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