Molybdenum Trivia Questions and Answers

  1. What is the atomic number of molybdenum?
    A: 41
    B: 42
    C: 43
    D: 44
    Correct Answer: B
    Explanation: Molybdenum has an atomic number of 42, placing it in group 6 of the periodic table.
  2. Which scientist first discovered molybdenum?
    A: Dmitri Mendeleev
    B: Marie Curie
    C: Carl Wilhelm Scheele
    D: Albert Einstein
    Correct Answer: C
    Explanation: Carl Wilhelm Scheele discovered molybdenum in 1778 by differentiating it from other minerals.
  3. In what year was molybdenum first isolated?
    A: 1780
    B: 1781
    C: 1782
    D: 1783
    Correct Answer: B
    Explanation: Molybdenum was first isolated by Peter Jacob Hjelm in 1781.
  4. Molybdenum has the highest melting point of any element except for how many other elements?
    A: Three
    B: Four
    C: Five
    D: Six
    Correct Answer: C
    Explanation: Molybdenum’s melting point is the sixth highest among naturally occurring elements. Only tantalum, osmium, rhenium, tungsten, and carbon have higher melting points.
  5. Which enzyme in humans requires molybdenum to function correctly?
    A: Lactase
    B: Xanthine oxidase
    C: DNA polymerase
    D: Amylase
    Correct Answer: B
    Explanation: Xanthine oxidase is a molybdenum-containing enzyme that helps in purine catabolism.
  6. What is the standard atomic weight of molybdenum?
    A: 94.95
    B: 95.95
    C: 96.95
    D: 97.95
    Correct Answer: B
    Explanation: The standard atomic weight of molybdenum is 95.95 g/mol.
  7. In terms of abundance, where does molybdenum rank in the Earth’s crust?
    A: 54th
    B: 40th
    C: 32nd
    D: 29th
    Correct Answer: A
    Explanation: Molybdenum is the 54th most abundant element in the Earth’s crust.
  8. Which molybdenum isotope is commonly used for generating a radioisotope used in medical imaging?
    A: Mo-92
    B: Mo-95
    C: Mo-98
    D: Mo-99
    Correct Answer: D
    Explanation: Molybdenum-99 is used to generate technetium-99m, which is used in medical imaging.
  9. What is the melting point of molybdenum?
    A: 2623 °C
    B: 2750 °C
    C: 2896 °C
    D: 3002 °C
    Correct Answer: A
    Explanation: Molybdenum has a melting point of 2623 °C (4753 °F).
  10. What is the primary ore from which molybdenum is extracted?
    A: Galena
    B: Wulfenite
    C: Molybdenite
    D: Sphalerite
    Correct Answer: C
    Explanation: Molybdenite (MoS2) is the principal ore from which molybdenum is extracted.
  11. In which body-centered crystal structure does molybdenum crystallize?
    A: Face-centered cubic
    B: Hexagonal close-packed
    C: Body-centered cubic
    D: Simple cubic
    Correct Answer: C
    Explanation: Molybdenum crystallizes in a body-centered cubic (bcc) structure.
  12. What is the common oxidation state of molybdenum in molybdenum disulfide (MoS2)?
    A: -2
    B: 0
    C: +4
    D: +6
    Correct Answer: C
    Explanation: In molybdenum disulfide (MoS2), molybdenum commonly exhibits an oxidation state of +4.
  13. Molybdenum is prominently used in which type of alloys for high temperatures?
    A: Mercury-based
    B: Superalloys
    C: Magnesium-based
    D: Zinc alloys
    Correct Answer: B
    Explanation: Molybdenum is used in superalloys that can withstand extreme temperatures, especially in steel.
  14. How many stable isotopes of molybdenum occur naturally?
    A: 4
    B: 5
    C: 6
    D: 7
    Correct Answer: D
    Explanation: Seven isotopes of molybdenum occur naturally: 92, 94, 95, 96, 97, 98, and 100.
  15. Which element is often used in conjunction with molybdenum in catalysts for hydrodesulfurization of petroleum?
    A: Iron
    B: Cobalt
    C: Calcium
    D: Nickel
    Correct Answer: B
    Explanation: Cobalt in combination with molybdenum is used as a catalyst in hydrodesulfurization of petroleum.
  16. Which compound is formed when molybdenum reacts with high temperature and air?
    A: Molybdenum oxide
    B: Molybdenum chloride
    C: Molybdenum sulfide
    D: Molybdenum nitride
    Correct Answer: A
    Explanation: Molybdenum reacts with high temperatures and air to form molybdenum trioxide (MoO3).
  17. What kind of bond is present in the diatomic molecule Mo2 in the gas phase?
    A: Double bond
    B: Triple bond
    C: Quadruple bond
    D: Sextuple bond
    Correct Answer: D
    Explanation: The diatomic molecule Mo2 in the gas phase has a sextuple bond.
  18. Which electron configuration represents molybdenum?
    A: [Kr] 4d5 5s1
    B: [Xe] 4d5 5s1
    C: [Kr] 5d1 6s2
    D: [Xe] 5d4 6s1
    Correct Answer: A
    Explanation: Molybdenum’s electron configuration is [Kr] 4d5 5s1.
  19. What is the molar heat capacity of molybdenum?
    A: 18.07 J/(mol·K)
    B: 24.06 J/(mol·K)
    C: 30.12 J/(mol·K)
    D: 35.73 J/(mol·K)
    Correct Answer: B
    Explanation: Molybdenum has a molar heat capacity of 24.06 J/(mol·K).
  20. Molybdenum has important biological roles especially in which kind of organisms?
    A: Animals only
    B: Plants only
    C: Bacteria, plants, and animals
    D: Fungi
    Correct Answer: C
    Explanation: Molybdenum is essential for various enzymes in bacteria, plants, and animals.
  21. How does molybdenum contribute to high-strength steel alloys?
    A: Enhances flexibility
    B: Increases corrosion resistance and strength
    C: Reduces density
    D: Promotes magnetic properties
    Correct Answer: B
    Explanation: Molybdenum contributes to high-strength steel alloys by increasing corrosion resistance and strength.
  22. What is the principal modern use of molybdenum in world production?
    A: Jewelry
    B: Steel alloys
    C: Rubber manufacturing
    D: Ceramics
    Correct Answer: B
    Explanation: The majority of molybdenum production, about 80%, is used in steel alloys.
  23. What is one of the key characteristics of molybdenum that makes it valuable in various applications?
    A: High elasticity
    B: High melting point
    C: Low electrical conductivity
    D: High ductility
    Correct Answer: B
    Explanation: Molybdenum’s high melting point makes it valuable for applications requiring extreme heat resistance.
  24. What percentage of the world’s molybdenum is produced in China?
    A: 24%
    B: 38%
    C: 56%
    D: 94%
    Correct Answer: D
    Explanation: China is the largest producer of molybdenum, accounting for about 94,000 tonnes, which represents a large fraction of world production.
  25. What type of bond can molybdenum form that is rarely seen with other elements?
    A: Single bond
    B: Quadruple bond
    C: Double bond
    D: Non-bond
    Correct Answer: B
    Explanation: Molybdenum can form quadruple bonds, a feature that is rarely seen among elements.
  26. How much molybdenum does an average human consume per day according to dietary recommendations?
    A: 10-50 μg per day
    B: 75-125 μg per day
    C: 150-200 μg per day
    D: 200-250 μg per day
    Correct Answer: A
    Explanation: The daily recommended intake varies, but typical recommendations are generally around 45 μg per day for adults.
  27. Which country discovered molybdenum-bearing grains on the Moon?
    A: USA
    B: USSR
    C: China
    D: Japan
    Correct Answer: B
    Explanation: The Soviet Luna 24 mission discovered molybdenum-bearing grains on the Moon.
  28. What is the boiling point of molybdenum?
    A: 3500 °C
    B: 4200 °C
    C: 4639 °C
    D: 4912 °C
    Correct Answer: D
    Explanation: Molybdenum has a boiling point of 4912 K (4639 °C, 8382 °F).
  29. What term is used to describe molybdenum’s occurrence in nature?
    A: Synthetic
    B: Isolation
    C: Primordial
    D: Volatile
    Correct Answer: C
    Explanation: Molybdenum occurs naturally in its primordial form.
  30. Which of the following is a key industrial use of molybdenum compounds?
    A: Wood varnish
    B: Pigments and catalysts
    C: Textile dye
    D: Plastic recycling agents
    Correct Answer: B
    Explanation: Molybdenum compounds are primarily used in pigments and catalysts for high-pressure and high-temperature applications.
  31. Which form of iron does molybdenum combine with in nitrogenase for nitrogen fixation?
    A: Iron(III) oxide
    B: Iron sulfide
    C: Iron–molybdenum cofactor (FeMoco)
    D: Hematite
    Correct Answer: C
    Explanation: The nitrogenase enzyme contains an iron–molybdenum cofactor (FeMoco) critical for nitrogen fixation.
  32. Which process in bacterial enzymes involves molybdenum?
    A: Photosynthesis
    B: Cellular respiration
    C: Nitrogen fixation
    D: Glycolysis
    Correct Answer: C
    Explanation: Molybdenum-bearing enzymes like nitrogenases play a crucial role in the process of nitrogen fixation in bacteria.
  33. What is the density of molybdenum at 20°C?
    A: 9.33 g/cm3
    B: 10.223 g/cm3
    C: 8.54 g/cm3
    D: 11.09 g/cm3
    Correct Answer: B
    Explanation: The density of molybdenum at 20°C is 10.223 g/cm3.
  34. Molybdenum trioxide (MoO3) is often used as a precursor for which applications?
    A: Electronics
    B: Microprocessors
    C: Alloys and various compounds
    D: Glass making
    Correct Answer: C
    Explanation: Molybdenum trioxide is the precursor to virtually all other Mo compounds as well as alloys.
  35. What is a significant feature of molybdenum hexacarbonyl?
    A: It’s a gas at room temperature
    B: Insoluble in water
    C: Forms quintuple bonds
    D: Zero oxidation state compound
    Correct Answer: D
    Explanation: Molybdenum hexacarbonyl is a zero oxidation state compound.
  36. Molybdenum is used to make which type of special steel due to its lower density compared to tungsten?
    A: M-Series high-speed steels
    B: Austenitic steel
    C: Ferritic steel
    D: Galvanized steel
    Correct Answer: A
    Explanation: Molybdenum is used to make the ‘M’ series of high-speed steels, serving as a substitution for the ‘T’ steel series that contain tungsten.
  37. Which compound is primarily used in applications related to heating elements?
    A: Molybdenum disulfide
    B: Molybdenum carbide
    C: Molybdenum disilicide (MoSi2)
    D: Molybdenum trioxide
    Correct Answer: C
    Explanation: Molybdenum disilicide (MoSi2) is used as a heating element for temperatures above 1500°C in air.
  38. Which of the following enzymes found in bacteria, plants, and animals contain molybdenum?
    A: Amylase
    B: Nitrogenase
    C: Polymerase
    D: Catalase
    Correct Answer: B
    Explanation: Nitrogenase is a molybdenum-containing enzyme found in bacteria involved in nitrogen fixation.
  1. What is the electronegativity of molybdenum on the Pauling scale?
    A: 1.5
    B: 2.16
    C: 2.5
    D: 3.0
    Correct Answer: B
    Explanation: Molybdenum has an electronegativity of 2.16 on the Pauling scale.
  2. Which alloys are known for incorporating molybdenum for its corrosion resistance?
    A: Aluminum alloys
    B: Austenitic stainless steels
    C: Copper alloys
    D: Brass
    Correct Answer: B
    Explanation: Molybdenum is used to enhance the corrosion resistance of austenitic stainless steels.
  3. What kind of particle accelerator commonly uses molybdenum’s isotope Mo-99?
    A: Synchrotron
    B: Linear accelerator
    C: Cyclotron
    D: Betatron
    Correct Answer: B
    Explanation: Mo-99 is typically produced in linear accelerators for medical applications.
  4. What natural phenomenon significantly integrates molybdenum into ecological cycles through oxidation states?
    A: Photosynthesis
    B: Tectonic movements
    C: Biological nitrogen fixation
    D: Evaporation
    Correct Answer: C
    Explanation: Biological nitrogen fixation integrates molybdenum into ecological cycles through its various oxidation states in molybdoenzymes.
  5. What is the predominant ion formed when molybdenum-bearing minerals contact oxygen and water?
    A: Molybdate ion (MoO4^2-)
    B: Chromate ion (CrO4^2-)
    C: Sulfate ion (SO4^2-)
    D: Phosphate ion (PO4^3-)
    Correct Answer: A
    Explanation: The molybdate ion (MoO4^2-) is quite soluble and forms when molybdenum-bearing minerals contact oxygen and water.
  6. What is a significant application of molybdenum disulfide?
    A: Fuel additive
    B: Solid lubricant
    C: Food preservative
    D: Insulating material
    Correct Answer: B
    Explanation: Molybdenum disulfide (MoS2) is widely used as a solid lubricant and a high-pressure high-temperature anti-wear agent.
  7. Molybdenum contributes to which type of battery technology for enhanced performance?
    A: Lead-acid batteries
    B: Nickel-cadmium batteries
    C: Lithium-sulfur batteries
    D: Zinc-air batteries
    Correct Answer: C
    Explanation: Molybdenum is used in lithium-sulfur batteries to improve performance and stability.
  8. Which process is used primarily to recover molybdenite from ores?
    A: Distillation
    B: Froth flotation
    C: Electrolysis
    D: Magnetic separation
    Correct Answer: B
    Explanation: Froth flotation remains the primary process for recovering molybdenite from ores.
  9. Which molybdenum compound is extensively used in pigments?
    A: Molybdenum disulfide (MoS2)
    B: Molybdenum oxide (MoO3)
    C: Lead molybdate (PbMoO4)
    D: Sodium molybdate (Na2MoO4)
    Correct Answer: C
    Explanation: Lead molybdate is used as a bright-orange pigment in ceramics and plastics.
  10. What is the primary use of molybdenum in the agricultural sector?
    A: Soil conditioner
    B: Fertilizer for specific plants
    C: Pest control chemical
    D: Crop rotation agent
    Correct Answer: B
    Explanation: Molybdenum powder is used as a fertilizer for specific plants such as cauliflower.
  11. What industrial application uses molybdenum for pollution control?
    A: Water filtration
    B: NOx analyzers in power plants
    C: Waste recycling
    D: Air purifiers
    Correct Answer: B
    Explanation: Elemental molybdenum is used in NOx analyzers in power plants for pollution control to convert NO2/NOx to NO molecules for detection.
  12. What property makes molybdenum an effective lubricating material under extreme conditions?
    A: High viscosity
    B: Low density
    C: High melting point
    D: Strong film formation on metals
    Correct Answer: D
    Explanation: Molybdenum disulfide forms strong films on metallic surfaces and is known for its lubricating properties under high-pressure and high-temperature conditions.
  13. What molybdenum alloy is known for its resistance to corrosion by molten salts?
    A: Tungsten-molybdenum alloy
    B: Copper-molybdenum alloy
    C: TZM alloy
    D: Chromium-molybdenum alloy
    Correct Answer: C
    Explanation: TZM is a molybdenum alloy known for its resistance to corrosion by molten fluoride salts at high temperatures.
  14. What is the CAS Number of molybdenum?
    A: 7439-96-5
    B: 7439-97-6
    C: 7439-98-7
    D: 7439-99-8
    Correct Answer: C
    Explanation: The CAS Number of molybdenum is 7439-98-7.
  15. Which molybdenum compound is used in the detection of phosphorus via spectroscopy?
    A: Molybdenum disulfide
    B: Phosphomolybdate anion
    C: Molybdenum hexacarbonyl
    D: Molybdenum trioxide
    Correct Answer: B
    Explanation: The phosphomolybdate anion (P[Mo12O40]3−) is used for the spectroscopic detection of phosphorus.
  16. How much molybdenum is typically found in the human body per kilogram of body weight?
    A: 0.007 mg
    B: 0.07 mg
    C: 0.7 mg
    D: 7 mg
    Correct Answer: B
    Explanation: The human body contains about 0.07 mg of molybdenum per kilogram of body weight.
  17. Molybdenum-containing fertilizers typically benefit which type of crops most?
    A: Root vegetables
    B: Leafy greens
    C: Legumes
    D: Grains
    Correct Answer: C
    Explanation: Molybdenum-containing fertilizers are particularly beneficial for legumes due to their role in nitrogen fixation.
  18. Which process produces significant amounts of molybdenum trioxide from molybdenum disulfide ore?
    A: Electrolysis
    B: Roasting in air
    C: Carbonation
    D: Sublimation
    Correct Answer: B
    Explanation: Molybdenum disulfide ore is roasted in air to produce molybdenum trioxide (MoO3).
  19. What impact does molybdenum have on the crystalline structure of steel?
    A: Causes brittleness
    B: Reduces hardness
    C: Increases ductility
    D: Introduces lattice strain
    Correct Answer: D
    Explanation: Molybdenum increases lattice strain in steel, thereby enhancing its strength and hardness.
  20. Which synthetic radioisotope derived from molybdenum is notably used in nuclear medicine?
    A: Tc-99m
    B: I-131
    C: Cs-137
    D: Co-60
    Correct Answer: A
    Explanation: The synthetic radioisotope technetium-99m (Tc-99m) derived from molybdenum-99 is widely used in nuclear medicine.
  21. In metallurgy, molybdenum is often used in combination with which element to improve ductility and weldability?
    A: Nickel
    B: Titanium
    C: Chromium
    D: Tungsten
    Correct Answer: C
    Explanation: Molybdenum is often combined with chromium in steel alloys to improve ductility and weldability.
  22. How is molybdenum most commonly excreted from the human body?
    A: Sweat
    B: Feces
    C: Urine
    D: Breath
    Correct Answer: C
    Explanation: Most molybdenum is excreted from the human body as molybdate in the urine.

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