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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 |