Q: You are asked to prepare 500 ml of 0.137 M NaCl solution. The molecular weight of NaCl is 58.44 g/mol. How many grams of NaCl are required?

$$0.137 \times 58.44 \times 0.5 = 4.01 g$$

Q: A student needs to prepare 200 ml of a solution having 25 mg/ml from a 100 mg/ml stock solution. What volume of stock solution should be used?

$$V_1$$ = \frac{$$C_2$$ \times $$V_2$$}{$$C_1$$} = \frac{25 \times 200}{100} = 50$$ ml

Q: During a serial dilution, if the dilution factors for three steps are DF$$_1 = 5$$, DF$$_2 = 10$$, and DF$$_3 = 2$$, what is the final dilution factor?

$$DF = DF_1$ \times DF_2$ \times DF_3$ = 5 \times 10 \times 2 = 100$$

Q: In paper chromatography, how is the R$$_f$$ value of a compound calculated?

$$R_f = \frac{\text{distance moved by the sample}}{\text{distance moved by the solvent}}$$

Q: A student wants to convert a 0.05 M solution of a chemical with molecular weight 125 to percent solution. What is the correct formula and answer?

$$\% \text{ Solution} = \text{Molarity} \times \text{Molecular weight} / 10 = 0.05 \times 125 / 10 = 0.625\%$$

Question 1

Which of the following best describes the principle behind the Biuret test for proteins?

Accepted Answer

It identifies peptide bonds by forming a colored complex with Cu$$^{2+}$$ ions in alkaline solution.

Question 2

You are asked to prepare 500 ml of 0.137 M NaCl solution. The molecular weight of NaCl is 58.44 g/mol. How many grams of NaCl are required?

Accepted Answer

$$0.137 	imes 58.44 	imes 0.5 = 4.01 g$$

Question 3

A student needs to prepare 200 ml of a solution having 25 mg/ml from a 100 mg/ml stock solution. What volume of stock solution should be used?

Accepted Answer

$$V_1$$ = \frac{$$C_2$$ 	imes $$V_2$$}{$$C_1$$} = \frac{25 	imes 200}{100} = 50$$ ml

Question 4

Which reagent is used in Millon's test to detect the presence of amino acids containing a hydroxybenzene radical?

Accepted Answer

Mercuric sulfate in sulfuric acid

Question 5

During a serial dilution, if the dilution factors for three steps are DF$$_1 = 5$$, DF$$_2 = 10$$, and DF$$_3 = 2$$, what is the final dilution factor?

Accepted Answer

$$DF = DF_1$ 	imes DF_2$ 	imes DF_3$ = 5 	imes 10 	imes 2 = 100$$

Question 6

Which test is most appropriate for distinguishing between reducing monosaccharides and reducing disaccharides?

Accepted Answer

Barfoed's test

Question 7

A solution is labeled as 10% w/v NaCl. What does this mean?

Accepted Answer

10 g of NaCl is dissolved in 100 ml of solvent.

Question 8

Which of the following statements about the solubility test for lipids is correct?

Accepted Answer

Lipids are soluble in organic solvents such as ether and chloroform.

Question 9

In paper chromatography, how is the R$$_f$$ value of a compound calculated?

Accepted Answer

$$R_f = \frac{	ext{distance moved by the sample}}{	ext{distance moved by the solvent}}$$

Question 10

Which of the following is a correct procedure for preparing a solution of known concentration from a solid material?

Accepted Answer

Weigh the solid, dissolve in a small volume of solvent, transfer to a volumetric flask, and dilute to the mark.

Question 11

Which test is used to detect the presence of pentose sugars in a sample?

Accepted Answer

Bial's test

Question 12

A student wants to convert a 0.05 M solution of a chemical with molecular weight 125 to percent solution. What is the correct formula and answer?

Accepted Answer

$$\% 	ext{ Solution} = 	ext{Molarity} 	imes 	ext{Molecular weight} / 10 = 0.05 	imes 125 / 10 = 0.625\%$$

Question 13

Which of the following is a correct interpretation of a positive Benedict's test?

Accepted Answer

The solution contains reducing sugars that reduce Cu$$^{2+} to Cu$_2O$$, forming a colored precipitate.

Question 14

Which test is used to detect the presence of ketose sugars in a sample?

Accepted Answer

Seliwanoff's test

Question 15

What is the main structural feature of lipids that determines their solubility in organic solvents?

Accepted Answer

Hydrophobic hydrocarbon chains

Question 16

Which of the following is the correct formula to convert percent solution to molarity?

Accepted Answer

$$	ext{Molarity} = \% 	ext{ solution} 	imes 10 / 	ext{Molecular weight}$$

Question 17

Which test is used to determine the unsaturation of fatty acids?

Accepted Answer

Bromine water test

Question 18

What is the main principle behind the emulsification test for lipids?

Accepted Answer

Emulsifiers increase the surface area of lipid droplets by stabilizing them in water.

Question 19

Which of the following statements about the ninhydrin test is correct?

Accepted Answer

Ninhydrin reacts with free amino groups to produce a purple color.

General Biochemistry Laboratory Techniques and Qualitative Analysis

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