BCH Week 1 - Lec 4 - Acids and Bases

what type of bonds do water molecules form with one another? what are the characteristics?

• water molecules form hydrogen bonds with one another

• each water molecule can bond with 4 others, creating a lattice structure, and is why water is so fluid

what is the chemical structure of water, and what bonds keep the atoms together?

• H-O-H

• held together by polar covalent bonds - excellent solvent for polar solutes

water is the main ____ in the body

• water is the main solvent in the body

  • a solution is a solute dissolved in a solvent

  • solvent surrounds solute → forms a solvation shell

what is water good at dissolving? and what is solubility?

• water is good at dissolving polar (hydrophilic) molecules because “like dissolves like”, and is poor with non-polar (hydrophobic)

• solubility refers to the ease with which a solute dissolves

describe the dissociation of water

• in very small amounts, water undergoes auto ionization and dissociates into H+ and OH-

• in pure water, the concentration of H+ is 1×10^-7 M

H2O < — > OH- + H+

what is pH? what is the pH of water? what does it mean when the pH is less or more than the pH of water?

• pH is a log scale used to measure the acidity or basicity of an aqueous solution

  • pH = -log [H+]

• pH of pure water is 7 - equal [OH-] and [H+]

  • every unit lower than 7 = 10 fold increase in H+ ion number

  • every unit greater than 7 = 10 fold decrease in H+ ion number

what are acids and bases?

molecules that can donate a proton are acids, and those that can accept them are bases

strong acids - how do they behave in water? what happens to the pH when when added to a solution?

• strong acids ionize completely in water and donate their H⁺

• i.e. HCl —> Cl- + H⁺

• adding a strong acid to solution increases H⁺ concentration, causing pH to decrease

strong bases - how do they behave in water? what happens to the pH when when added to a solution?

• strong bases also ionize completely in water and donate their OH⁻

• adding a strong base to solution increases OH⁻ concentration, causing pH to increase