16 4 Titrations EQUIVALENCE POINT the point in the titration when the of moles of acid is stoichiometrically equal to the of moles of base Titration of a strong substance with a strong substance generates a pH of 7 00 at equivalence point TITRATION OF A STRONG ACID W A STRONG BASE PROBLEM Calculations 1 Find the Volume of Base needed to reach equivalence point step 1 go from mL to L to moles of acid this is also to the moles of base because at equivalence point they are equal step 2 use the concentration of the base to go from moles to L vol 2 Find initial pH of the solution before titration step1 this is before the base is added so the only thing present is the acid and water Since this is a strong acid the concentration of the acid is also the concentration of H3O step 2 plug that concentration into pH log H3O to get pH 3 Find pH before equivalence point step 1 go from mL of added base to L of added base to moles of added base step 2 do a before add after chart to calculate the amount of acid that is left in moles step 3 convert acid from moles to M which is equal to the amount of H3O ions and then you can get pH 4 pH at equivalence point this is always 7 00 5 Find the pH after equivalence point step 1 go from mL to L to moles of added base Then subtract the number of moles of base required to reach equivalence point This will give you the amount of leftover base in moles that effects pH step 2 divide the leftover moles of base by the total L of solution to find the concentration of the base M Since it is a strong base that also equals the amount of OH ions From here you can take the log OH to find pOH Then do 14 pOH pH TITRATION OF A WEAK ACID W A STRONG BASE PROBLEM Calculations 1 Find the Volume of Base needed to reach equivalence point step 1 go from mL to L to moles of acid this is also to the moles of base because at equivalence point they are equal step 2 use the concentration of the base to go from moles to L vol 2 Find initial pH of the solution before titration step1 this is before the base is added so the only thing present is the acid and water Since this is a weak acid use an ice table to find the concentration of H3O step 2 plug that concentration into pH log H3O to get pH 3 Find pH before equivalence point step 1 go from mL of added base to L of added base to moles of added base step 2 do a before add after chart to calculate the amount of acid that is left and the amount of conjugate base that has been produced in moles step 3 use the Henderson Hasslebalch equation to get pH 4 pH at equivalence point step 1 go from mL of added base to L of added base to moles of added base step 2 do a before add after chart to calculate the amount of conjugate base that has been produced in moles since products are the only thing left in the solution that hasn t reacted Then find the concentration M of the conj Base step 3 make a new equation with the conj Base water the original acid and OH Then do an ice chart to find the concentration of OH step 4 find pOH then 14 pOH pH 5 Find the pH after equivalence point step 1 go from mL to L to moles of added base Then subtract the number of moles of base required to reach equivalence point This will give you the amount of leftover base in moles that effects pH step 2 divide the leftover moles of base by the total L of solution to find the concentration of the base M Since it is a strong base that also equals the amount of OH ions From here you can take the log OH to find pOH Then do 14 pOH pH
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