Structure Of Organic Molecules

1.

The following are special properties of carbon except....

A.

The ability to catenate
B.

Tetrahedral geometry
C.

Presence of 6 electrons in it's outer shell
D.

The ability to form only single bonds with other elements

Correct Answer
D. The ability to form only single bonds with other elements

Explanation
Carbon is known for its ability to form multiple bonds with other elements, not just single bonds. This property allows carbon to form a wide variety of compounds, including complex organic molecules. Carbon's ability to catenate refers to its unique ability to form long chains and rings with other carbon atoms. Tetrahedral geometry is another special property of carbon, where it forms four bonds with other atoms in a tetrahedral arrangement. Lastly, carbon typically has 4 valence electrons in its outer shell, not 6.

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2.

One of the following is not a marcromolecules in living organisms

A.

Carbohydrate
B.

Glycerol
C.

Nucleic acid
D.

Proteins

Correct Answer
B. Glycerol

Explanation
Glycerol is not considered a macromolecule in living organisms because it is a small molecule that is a component of lipids, such as triglycerides. Macromolecules, on the other hand, are large molecules made up of repeating subunits. Carbohydrates, nucleic acids, and proteins are all examples of macromolecules found in living organisms. Carbohydrates are composed of sugar molecules, nucleic acids are made up of nucleotide subunits, and proteins are built from amino acids. Glycerol, although important in cellular metabolism, does not meet the criteria of a macromolecule.

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3.

Boiling points of substances decrease about 0.5C for each ........ decrease in atmospheric pressure.

A.

15-mm
B.

5-mm
C.

10-mm
D.

20-mm

Correct Answer
C. 10-mm

Explanation
The boiling points of substances decrease about 0.5C for each 10-mm decrease in atmospheric pressure. This means that as the atmospheric pressure decreases, the boiling point of a substance also decreases. A decrease in atmospheric pressure reduces the pressure exerted on the substance, allowing its molecules to escape more easily, leading to a lower boiling point. Therefore, a 10-mm decrease in atmospheric pressure would result in a decrease of about 0.5C in the boiling point of the substance.

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4.

Temperature at which vapor pressure of the liquid equals the pressure of the atmosphere above it is ________

Correct Answer
boiling point

Explanation
The boiling point of a liquid is the temperature at which its vapor pressure is equal to the pressure of the atmosphere above it. At this temperature, the liquid starts to rapidly vaporize and form bubbles throughout the entire liquid. This is why boiling occurs, and it is a clear indication that the liquid has reached its boiling point.

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4

5.

Impurities will ......... the melting point and ......... the boiling point

A.

Raise, increase
B.

Lower, raise
C.

Raise, lower
D.

Decrease, lower

Correct Answer
B. Lower, raise

Explanation
Impurities in a substance disrupt the regular arrangement of its molecules, making it more difficult for them to move freely. This results in a decrease in the melting point, as the substance requires less energy to transition from a solid to a liquid state. On the other hand, impurities also increase the boiling point by increasing the boiling point elevation. This occurs because the impurities create additional sites for vaporization, requiring more energy to reach the boiling point. Therefore, impurities lower the melting point and raise the boiling point.

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6.

In TLC, the stationary phase is liquid whiles the mobile phase is solvent.

A.

True
B.

False

Correct Answer
B. False

Explanation
The given statement is false. In TLC (Thin Layer Chromatography), the stationary phase is a solid material, usually a thin layer of silica gel or alumina, coated on a glass or plastic plate. The mobile phase, on the other hand, is a liquid solvent that moves over the stationary phase by capillary action. The different components of the mixture being analyzed in TLC will interact differently with the stationary phase, causing them to separate and form distinct spots on the plate.

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7.

A method used to separate a solvent from a solution containing non-volatile solutes is .......

A.

Recrystallization
B.

Distillation
C.

Sublimation
D.

Solvent solvent extraction

Correct Answer
B. Distillation

Explanation
Distillation is a method used to separate a solvent from a solution containing non-volatile solutes. It involves heating the solution to vaporize the solvent, then condensing the vapor back into a liquid to collect the purified solvent. This process takes advantage of the different boiling points of the solvent and solutes, allowing for their separation. Recrystallization involves dissolving the solute in a hot solvent and allowing it to cool, causing the solute to crystallize out of the solution. Sublimation is the process of converting a solid directly into a gas without going through the liquid phase. Solvent extraction involves using a different solvent to selectively extract the desired solute from the solution.

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8.

Infrared (IR) spectrum determines the presence of functional groups of an organic compound.

A.

True
B.

False

Correct Answer
A. True

Explanation
The statement is true because infrared (IR) spectrum is commonly used in organic chemistry to identify the presence of specific functional groups in a compound. Each functional group absorbs infrared radiation at characteristic frequencies, allowing scientists to analyze the spectrum and determine the types of functional groups present. This information is crucial in identifying and characterizing organic compounds.

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9.

Nuclear magnetic resonance (NMR), determines the structure of organic compounds

A.

True
B.

False

Correct Answer
A. True

Explanation
Nuclear magnetic resonance (NMR) is a technique used to determine the structure of organic compounds. It involves the interaction of atomic nuclei with an external magnetic field, which produces a unique signal that can be used to identify the compound's structure. By analyzing the NMR spectrum, scientists can determine the types and positions of atoms within the molecule, as well as gain insights into its chemical environment. Therefore, the statement "Nuclear magnetic resonance (NMR) determines the structure of organic compounds" is true.

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10.

Mass spectrometry is used to determine ________

Correct Answer
molecular weight

Explanation
Mass spectrometry is a technique used to determine the molecular weight of a compound. It works by ionizing the compound and then separating the ions based on their mass-to-charge ratio. By measuring the mass of the ions, the molecular weight of the compound can be determined. This is useful in various fields such as chemistry, biochemistry, and pharmaceuticals, where knowing the molecular weight of a compound is important for understanding its structure and properties.

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4

11.

Which one do you like?

A.

Option 1
B.

Option 2
C.

Option 3
D.

Option 4

Correct Answer
A. Option 1

Explanation
The explanation for why Option 1 is the correct answer is not available as the question does not provide any additional context or criteria to determine a preference.

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