Solution Concentration: Molarity Molarity = moles solute per liter of solution 0.30 mol NH3 dissolved in 0.500 L Concentration = Written like: [NH3] = 0.60 M

pH: Quantitative Measure of Acidity Acidity is related to concentration of H+ pH = -log[H+] [H+] = 10-pH

pH Scale In pure water, a few molecules ionize to form H+ and OH– H2O  OH– + H+ In acidic and basic solutions, these concentrations are not equal acidic: [H+] > [OH–] basic: [OH–] > [H+] neutral: [H+] = [OH–]

pH Scale Measure how much H+ is in a solution using pH pH < 7.0 = acidic pH = 7.0 = neutral pH > 7.0 = basic Measure of H+ and OH– concentration (moles per liter) in a solution As acidity increases, pH decreases

pH = –log [H+] The pH scale is logarithmic: [H+], mol/L -log[H+] 10 101 -log(101) = -1 1 100 -log(100) = 0 0.1 100 -log(10-1) = 1 0.01 10–1 -log(10-2) = 2 0.0001 10-4 -log(10-4) = 4 1 x 10-9 10–9 -log(10-9) = 9

[H+] pH Calculations What is pH if [H+] = 10–5 M? Is a solution with [H+] = 10–8 M? Acidic or basic? What is pH if [H+] = 0.000057 M? What is [H+] if pH = 4.68?

Molarity is a conversion factor Moles Liters

Solution Stoichiometry Example 1. What is mass of PbCrO4 produced when 50.0 mL of a 0.400 M Pb(NO3)2 solution is mixed with an excess of 0.100 M K2CrO4?

CaCO3 + 2 HNO3  Ca(NO3)2 + CO2 + H2O Calculate the volume (in mL) of 0.715 M HNO3 needed to react completely with 6.35 g of CaCO3. CaCO3 + 2 HNO3  Ca(NO3)2 + CO2 + H2O

Titration Example Problems: Just like your lab! 1. Standardizing an NaOH solution using a “primary standard” A solution of sodium hydroxide is “standardized” by titration using solid oxalic acid, H2C2O4, as the acid. It is found that 24.5 mL of the NaOH solution is needed to react completely with 2.05 g of oxalic acid. What is the concentration of the NaOH solution? H2C2O4(aq) + 2 NaOH  2 H2O(l) + Na2C2O4(aq)