pH and Titration Notes Chemistry

pH  measure of the strength of acids and bases  pH = power of hydrogen  pH = -log [H + ]  logarithmic scale – so when you change a number on the scale, you change by a factor of 10  pH 3 is 10 times less acidic than pH 2  pH 1 is 100 times more acidic as pH 3

pH of Common Substances

pOH  measures strength of the hydroxide ion  pOH = -log [OH - ]  highest value of pH or pOH = 14  lower value of pOH = stronger base  pH + pOH = 14  if find one of the values, then subtract from 14 to find the other  example: if pH is 3, then pOH is 11 (14-3 = 11)

Neutralization  reaction between an acid and a base in which their acidic and basic properties disappear  Acid + Base  Salt + Water  salt = metal and a non-metal  ex. HCl + NaOH  NaCl + H 2 O  ex. HCl + Ca(OH) 2  CaCl 2 + H 2 O

Titration  technique used by chemists to determine the unknown concentration of a substance using a neutralization reaction  uses an indicator to tell when reaction has reached neutralization  indicator – chemical that is one color in an acid and another color in a base  end point – the point in the reaction when neutralization has occurred and the indicator changes color

Acid-Base Indicators  An acid – base indicator changes color when it is in a solution of a certain pH.  Red litmus paper turns blue and is used as an indicator of a basic solution that would have a pH above 7.  Blue litmus paper turns red and is used as an indicator of an acidic solution that would have a pH below 7.  Phenolphthalein is also a common kind of acid – base indicator. It turns clear in an acid and pink in a base.  chapter6/lesson8#proton_transfer_illustration chapter6/lesson8#proton_transfer_illustration

Titration Equation  when reaction in titration is neutral, moles of acid = moles of base  moles = molarity (M) x volume (V)  so use the equation: Moles Acid = Moles Base M 1 V 1 = M 2 V 2

Titration Example 1  What is the molarity of a CsOH solution if 30.0 mL of the solution is neutralized by 26.4 mL of a M HBr solution?

Titration Example 2  What is the molarity of a nitric acid solution if mL of a M KOH solution is needed to neutralize 20.0 mL of HNO 3 ?

Titration Example 3  What is the concentration of a household ammonia cleaning solution if 49.9 mL of a 0.59 M HCl solution is required to neutralize 25.0 mL of ammonia solution?

Titration Example 4  A titration of 50 mL of an unknown concentration of NaOH solution uses a 0.5 M HCl solution. The buret containing HCl initially reads 49.8 mL and reads 22.5 mL after the end point is reached. What is the molarity of the NaOH solution?