Neutralization, Titration & Concentration

Neutralization For an acid to effectively neutralize a base (or vice versa) the number of moles of acid and base must be equal

Example How many moles of sodium hydroxide are required to neutralize 45.0 mL of a mol/L H 2 SO 4 solution? 1. Write a balanced equation.

2NaOH (aq) + H 2 SO 4(aq)  2H 2 O (l) + Na 2 SO 4(aq) 2. Determine the # of moles to be neutralized (calculate the number of moles of H 2 SO 4 )

2NaOH (aq) + H 2 SO 4(aq)  2H 2 O (l) + Na 2 SO 4(aq) 3. Use the coefficients to calculate the number of moles required for neutralization.

Extension 2NaOH (aq) + H 2 SO 4(aq)  2H 2 O (l) + Na 2 SO 4(aq) 4. If you used 30.0 mL of NaOH to neutralize the H2SO4, what is the concentration of the NaOH?

Titrations Requirements: – Standard  an acid or base where you know the [concentration] – Indicator  a substance in which the completed titration (change from acidic to basic or vice versa) will be demonstrated by a colour change

Titrations cont’d When the concentration of the acid and the base are equal, we have reached the “equivalence point” This is where: #Moles acid = #moles base The end point is reached when one drop of titrate permanently changes the colour of the indicator

Vinegar (aka Acetic Acid) was titrated with Sodium Hydroxide to determine the concentration of acetic acid present. A volume of 41.6 mL of 1.00 mol/L NaOH was required to neutralize a 50.0 mL sample of vinegar, indicated by a pink colour change. What was the concentration of the vinegar? 1. Write a balanced equation

2. Calculate the moles of the standard that were required to neutralize the unknown concentration of vinegar * At the equivalence point the moles acid = moles base

NaOH (aq) + CH 3 COOH (aq)  CH 3 COONa (aq) + H 2 O 3. Use the coefficients to figure out the mole ratio (notice it is 1:1 in this equation and therefore #moles CH 3 COOH = #moles NaOH

Calculate the concentration of CH 3 COOH

Example: How many moles of sodium hydroxide are required to neutralize 0.20 moles of nitric acid?

Example: How many millilitres of 0.45 mol/L HCl solution must be added to 25.0 mL of a 1.00 mol/L KOH solution to make a neutral solution?