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Lecture 4

FDSN 507 Midterm 1

Define total acidity. Measure of the total acid concentration; affects flavor; indicator of maturity.
Define pH. Measure of free hydrogen ions; active acidity.
Define normality. Represents the number of moles of H+ or OH- per liter that will be exchanged in a neutralization reaction.
Define equivalent weight. molecular weight/number of moles equivalent
Define percent concentration. The ratio of weight or volume of solute to the weight or volume of solute plus solvent.
Define Kw. The ion product constant for water.
A pH meter is also known as a _______. potentiometer
What does a pH meter measure? Voltage at an infinitesimal current.
What are the three parts of a pH meter? Reference electrode, indicator electrode, voltmeter
Give two methods to determine the end point for titratable acidity. pH meter, indicator dye
Titratable acidity is expressed in terms of predominant _____ _____. organic acid
Define buffering. When a solution resists a change in pH.
When does maximum buffering occur? pH=pKa
What does it mean when pH = pKa? Equal quantities of undissociated acid and conjugate base.
Define equivalence point. The amount of acid equivalence equals the number of base equivalence.
The use of a pH meter to identify the endpoint in TA determination is called ______ method. potentiometric
What is the pH of a phenolphthalein endpoint? 8.2
T or F: Food generally do not buffer at pH 8.2. True
What is Brix/acid ratio used for? To predict acid flavor; useful to determine the maturity of fruits.
T or F: Brix/acid ratio tends to decrease with fruit maturity. False
Volatile acidity =____ acidity - _____ acidity. total, fixed
Volatile acidity is a quality indicator for _____. wine
Created by: goberoi