Tuesday, May 31, 2011

PH of milk and water?

1. With acid addition, does pH drop faster or slower in the milk, as compared to the water? Why?



2. How does the presence of suspended protein in the milk affect the pH change brought about by adding a given amount of acid?



3. What is the relative strength of vinegar and acetic solutions? What is the chemical nature of vinegar?PH of milk and water?
1. With acid addition, does pH drop faster or slower in the milk, as compared to the water? Why?



Slower, because milk has buffer capacity. The two most important buffer components of milk are caseins (buffer maximum near pH 4.6) and calcium phosphate (buffer maxima near pH 7.0).



2. How does the presence of suspended protein in the milk affect the pH change brought about by adding a given amount of acid?



Suspended protein, much of which is casein, is an effective buffer in milk, reducing the amount of pH change caused by the addition of acid.



3. What is the relative strength of vinegar and acetic solutions? What is the chemical nature of vinegar?



They are both composed of water and acetic acid, also known as ethanoic acid, which is the organic chemical that gives vinegar its sour taste and pungent smell.



Acetic acid is a weak, effectively monoprotic acid in aqueous solution, and a 1 molar solution has a pH of 2.4. Vinegar generally has an acetic acid concentration lower than 1 M., and contains other ingredients, so its pH is slightly higher, usually ranging from 2.4 to 3.4.



Vinegar is an acidic liquid processed from the fermentation of ethanol in a process that yields its key ingredient, acetic acid (also called ethanoic acid). It also may come in a diluted form. The acetic acid concentration typically ranges from 4 to 8 percent by volume for table vinegar (typically 5%) and higher concentrations for pickling (up to 18%). Natural vinegars also contain small amounts of tartaric acid, citric acid, and other acids. Vinegar has a density of approximately 0.96 g/mL. The density level depends on the acidity of the vinegar. Household vinegar used for cooking is 1.05 g/mL.

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