Free Analytical Chemistry MCQs with Answers

71. In the mass spectrum of an organic compound, the molecular ion occurs at m/e of 86. Which of the following could be the empirical formula of the compound?

• A. C2H4
• B. C5H11N
• C. C7H13O
• D. C2H5F

Explanation: b) C5H11N:The molecular ion occurs at m/e 86. The empirical formula C5H11N corresponds to the compound pentylamine, which has a molecular mass of 87 g/mol. The molecular ion at m/e 86 is close to the molecular mass of pentylamine, so it is possible that this compound could have a molecular ion at m/e 86. Therefore, option b) C5H11N could be a possible empirical formula.

72. Which compound will not give positive chromyl chloride test?

• A. CuCl2
• B. ZnCl2
• C. HgCl2
• D. C4H9NH4+Cl-

Explanation: d) C4H9NH4+Cl- (Tetra-n-butylammonium chloride):Tetra-n-butylammonium chloride is a quaternary ammonium salt and does not contain a metal ion. Therefore, it will not react with chromyl chloride to produce the characteristic color. Hence, this compound will not give a positive chromyl chloride test.

73. The purity of diamond is judged by:

• A. Texture of surface
• B. Hardness
• C. Passing X-rays
• D. Placing in magnetic field

Explanation: The explanation for this question will be added soon.

74. The breakdown of molecular ions from natural products gives important information about?

• A. Size
• B. Position
• C. Shape
• D. Structure

Explanation: The breakdown or fragmentation of molecular ions from natural products, typically obtained by techniques such as mass spectrometry, can provide important information about the structure, composition, and identity of the natural product.

75. The mobile phase in paper chromatography is usually:

• A. A non-polar organic solvent
• B. Water
• C. Sulfuric acid
• D. Silver nitrate

Explanation: The correct answer is a non-polar organic liquid. In paper chromatography, the mobile phase is typically a non-polar organic solvent that moves up the paper, carrying the different components of the mixture with it. This helps separate the components based on their affinity to the stationary phase, which is usually water (a polar substance) within the paper. This polarity difference is crucial for separation. Water is incorrect as it serves as the stationary phase. Sulphuric acid and silver nitrate are not used as mobile phases in this technique due to their inappropriate properties for chromatography.

76. Paper chromatography is used for:

• A. Elemental Analysis
• B. Qualitative Analysis
• C. Industrial Purification
• D. Structural Analysis

Explanation: Explanation:Chromatography is very useful for organic synthesis for separation, purification, and isolation of products. They are equally important for quantitative and qualitative analysis and for determination of purity of a substance. Elemental analysis involves determining the elemental composition of a substance. Paper chromatography is not used for this purpose since it separates components based on their physical properties rather than their elemental composition.Industrial purification typically involves separating and purifying a specific component from a mixture at a large scale. Paper chromatography is not commonly used for industrial purification. Paper chromatography is used for qualitative analysis, not for structural analysis.

77. The purity of a substance can be identified by:

• A. Sublimation
• B. Filtration
• C. Chromatography
• D. Solvent extraction

Explanation: A is incorrect as sublimation purifies solids rather than identify themB is incorrect as filtration separates insoluble solutes from solvents.C is correct as chromatography is a tool to separate different solvents in a solute and their purification.D is incorrect as solvent extraction only extracts solutes,but doesnt identify them.

78. Chromyl Test is performed to confirm:

• A. Cl− ions
• B. SO4−2 ions
• C. PO4−3 ions
• D. Cr+3 ions

Explanation: Explanation:The chromyl chloride test is performed to detect chloride ions in the qualitative analysis. When any chloride salt for example sodium chloride (NaCl) is heated with acidified potassium dichromate, it gives fumes of chromyl chloride which is used to be in orange-red color. This confirms the presence of chloride ions in the salt.The chromyl test is not used to confirm the presence of sulfate ions (SO4-2). The chromyl test is not used to confirm the presence of phosphate ions (PO4-3). The chromyl test is also not used to confirm the presence of chromium ions (Cr+3).

79. The relative abundance of the isotopes of the elements can be determined by:

• A. Mass Spectrometry
• B. X-rays
• C. Chromatography
• D. Solvent Extraction

Explanation: A is correct as mass spectrometry is a method to differentiate between different isotopes of an element.B is incorrect as X-ray cant be used to differentiate between different isotopes of an element.C is incorrect as chromatography is used to differentiate between different solvents.D is incorrect as solvent extraction is a method to extract a soluble solute from a solution.

80. The type and relative amount of each isotope in an element can be found by:

• A. R spectroscopy
• B. U.V spectroscopy
• C. Mass Spectrometry
• D. N.M.R

Explanation: Mass Spectrometry (MS) is an analytical technique used to measure the mass-to-charge ratio of ions. It provides detailed information about the molecular weight and structure of compounds