40 Questions
What is the colored part of the citrus peel called?
Flabelo
What is the main component of the mesocarp?
Cellulose
What is the purpose of heating the sample in the titration process?
To eliminate the antiferment
What is the equation used to calculate the acidity percentage?
((ml.gastados de NaOH 0.1 N) (0.009)) / (ml.de muestra) x 100
What is the equivalent of citric acid for 0.1N NaOH?
0.0064
What is the edible part of the citrus fruit?
Endocarp
Why is it necessary to perform dilutions when expressing the results as citric acid hydrate?
To obtain accurate results
What is the purpose of the titration process?
To calculate the acidity percentage
What are the indicative parameters of poor milk quality?
pH level and bacterial count
What is the purpose of the titrations in laboratory chemistry?
To determine the concentration of an acid or a base in a solution
What is the normal value of protein in milk in Mexico?
3.5%
What is the pH range of fresh milk?
pH 6.5 to 6.7
What is the function of fenolftaleína in the titration of milk?
It is an indicator used to detect the endpoint of the titration
What are the main lipids present in emulsion in cow milk?
Triglycerides and cholesterol
What is the term for the acidity of milk that is due to the presence of phosphates, proteins, citrates, and CO2?
Acidity aparente
What is the primary purpose of analyzing milk quality?
To ensure food safety and quality
What can affect the quality of milk?
All of the above
What is the term for the difference between the titrable acidity and the apparent acidity of milk?
Acidity real
What is the minimum acidity percentage of milk that must be rejected after detecting its odor?
0.18%
What is the main consequence of consuming poor-quality milk?
Foodborne illness
What is the primary component of milk?
Water
What is the characteristic smell of sour milk due to?
The subproducts of lactate fermentation
What is the purpose of milk emulsion?
To stabilize fat and water
What is the purpose of the Universal Support in the laboratory setup?
To support the equipment
What is the purpose of determining the lactose percentage in milk?
To detect if the milk has been adulterated with water or if it comes from cows with mastitis
What is the name of the method used to determine the lactose percentage in milk?
Fehling method
What is the concentration of acid benzoic in the solución acuosa used to prepare the lactose standard solution?
2% w/v
What is the volume of the volumetric flask used in the experiment?
100 ml
What is the purpose of the reactivo Fehling A and B?
To react with the lactose and indicate the endpoint of the titration
What is the type of lactose used to prepare the standard solution?
Lactose anhydrate
What is the indicator used in the titration process?
Azul de metileno
What is the amount of lactose anhydrate dissolved in 1 liter of solución acuosa to prepare the standard solution?
10 grams
What is the objective of this laboratory practice?
To analyze the Vitamin C content in citrus fruits
What is the name of the acid used in this laboratory practice?
Ascorbic acid
What is the role of starch in this laboratory practice?
As an indicator
What is the function of Vitamin C in the human body?
To control some chemical reactions
Which of the following is not a substance used in this laboratory practice?
Sodium Chloride
What is the purpose of using Potassium Iodide in this laboratory practice?
To react with Ascorbic acid
What is the concentration of Sulfuric acid used in this laboratory practice?
0.3 M
What type of fruits are used in this laboratory practice?
Citrus fruits
Study Notes
Acidity of Milk
- Milk is amphoteric, meaning it can exhibit both acidic and basic properties.
- Fresh milk has a pH of 6.5-6.7, making it slightly acidic.
- When titrated with an alkaline solution using phenolphthalein as an indicator, milk yields an average acidity of 0.14% expressed as lactic acid, known as apparent acidity.
- This acidity is due to the presence of phosphates, proteins, citrates, and CO2, not the lactic acid produced by microbial contamination.
- The difference between titratable acidity and apparent acidity is called real acidity.
- This test is valuable for classifying milk, and milk with acidity above 0.18% should be rejected.
Determination of Lactose
- The objective is to determine the percentage of lactose (disaccharide) in milk using the Fehling method.
- The reactants used are Fehling's A and B solutions.
- The procedure involves titrating a milk solution with the Fehling's solutions to determine the amount of lactose in grams equivalent to 1 ml of Fehling's solution.
Vitamin C Analysis
- Vitamin C is also known as ascorbic acid.
- It is an essential nutrient in the human diet and plays a crucial role in enzyme systems.
- Vitamin C is present in various foods, especially citrus fruits.
- The objective is to analyze the vitamin C content in citrus fruits using a semiquantitative method.
- The reaction between ascorbic acid and iodine is used, with starch as an indicator.
Laboratory Equipment and Materials
- The laboratory equipment used includes:
- Pipettes (10 ml, 25 ml)
- Burette
- Volumetric flask (100 ml)
- Erlenmeyer flask
- Measuring cylinder
- Stirring rod
- Bunsen burner
- The materials used include:
- Sodium hydroxide (0.1 N)
- Phenolphthalein (1%)
- Distilled water
- Milk and cream samples
- Lactose
- Fehling's A and B solutions
- Starch
- Iodine
- Potassium iodide
A laboratory experiment on acid-base titration, involving the use of burettes, pipettes, and reagents to determine the concentration of an acid or base in a solution. This quiz is based on the procedures and reactions in the lab.
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