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Question 1:
Which of the following best describes the coordination number for a face-centered cubic structure?
Topic: Coordination Numbers in Crystal Structures
Correct Answer: A) 6
Detailed Hint:
- The coordination number is defined as the total number of nearest neighbors of a central atom in a molecule or a crystal.
- The Face-Centered Cubic (FCC) structure, specifically in the context of an NaCl crystal, exhibits a coordination number of 6.
- In an FCC structure, each sodium ion (Na+) is surrounded by six chloride ions (Cl-), and similarly, each chloride ion is surrounded by six sodium ions.
- Therefore, the correct answer is A, "6".
Question 2:
What is Bucky balls an Allotropic form of?
Topic: Allotropes of Elements
Correct Answer: B) Carbon
Detailed Hint:
- Allotropes are different forms of the same element in the same state of matter, having distinct physical and chemical properties.
- Among the options given, 'Bucky balls' is an allotropic form of the element Carbon.
- Bucky balls, also known as fullerenes, are molecules of carbon in the form of a hollow sphere, tube, or many other shapes.
- They derive their name from their resemblance to architect Buckminster Fuller's Geodesic domes.
- Therefore, the correct answer is B, "Carbon".
Question 3:
What form does a cubic crystal of NaCl take when 10% urea is present in its solution?
Topic: Impurities and Crystal Structure
Correct Answer: C) Needle like
Detailed Hint:
- The presence of impurities in a solution can significantly alter the crystallization process and the resulting crystal shape.
- When 10% urea is present as an impurity in an NaCl solution, the normally cubic crystals of NaCl change shape to resemble needles.
- This is due to the specific interaction between the NaCl and the urea molecules in the solution.
- Hence, the correct answer is C, "Needle like".
Question 4:
What are the unit cell dimensions in an orthorhombic crystal?
Topic: Crystal Systems and Their Dimensions
Correct Answer: B) a≠b≠c, α=β=γ=90°
Detailed Hint:
- The unit cell of a crystal is the smallest repeating structure that displays the full symmetry of the crystal structure.
- In an orthorhombic crystal system, the unit cell dimensions display three unequal axes (a, b, and c), all intersecting at right angles (90°).
- This characteristic distinguishes it from other crystal systems where the axes may be of equal length or may not intersect at right angles.
- Therefore, the correct answer is B) "a≠b≠c, α=β=γ=90°".
Question 5:
Which category of solids are referred to as "true solids"?
Topic: Classification of Solids
Correct Answer: C) Crystalline
Detailed Hint:
- The term "true solids" is often used to describe solids that maintain a consistent, orderly, and repeating pattern in their molecular arrangement.
- Among the options, only Crystalline solids possess this property.
- They are characterized by a highly ordered and repeating pattern that extends throughout the whole crystal.
- Examples of Crystalline solids include common table salt and many types of minerals.
- Thus, the correct answer is C, "Crystalline".
Question 6:
What type of crystal is formed by the molecules of CO₂ in dry ice?
Topic: Types of Crystals
Correct Answer: C) Molecular crystals
Detailed Hint:
- Crystals can be classified into various types based on the nature of the bonds holding the atoms or molecules together.
- In the case of dry ice, which is solid CO₂, the molecules are held together in the crystal structure, rather than individual carbon or oxygen atoms.
- Therefore, it forms what is known as a molecular crystal.
- Hence, the correct answer is C, "Molecular crystals".
Question 7:
How would you characterize the viscosity of an ideal solid?
Topic: Viscosity in Solids
Correct Answer: A) Infinite
Detailed Hint:
- Viscosity is a measure of a substance's resistance to deformation under stress. It is commonly associated with liquids, but it also applies to solids.
- An ideal solid is defined as a material that will not deform regardless of the amount of stress applied, implying that its viscosity is infinite.
- Unlike an ideal fluid, which has no viscosity and offers no resistance to strain, an ideal solid resists any deformation.
- Hence, the correct answer is A, "Infinite".
MCQs 8:
Into how many categories can the crystal lattice of a substance be classified?
Topic: Classification of Crystal Lattices
Correct Answer: B) Seven types
Detailed Hint:
- The crystal lattice of a substance represents the arrangement of particles in a crystalline solid.
- This arrangement can be classified into different types, known as Bravais lattices.
- There are 14 Bravais lattices, but they are typically grouped into seven lattice systems: triclinic, monoclinic, orthorhombic, tetragonal, rhombohedral, hexagonal, and cubic.
- Therefore, the correct answer is B, "Seven types".
MCQs 9:
What is the transition temperature of Tin (Sn)?
Topic: Transition Temperatures in Metals
Correct Answer: C) 13.2°C
Detailed Hint:
- The transition temperature is the precise temperature at which a substance can exist in two distinct crystalline forms in equilibrium.
- For Tin (Sn), a metallic element, this temperature is the point at which it changes from one crystalline form to another.
- The transition temperature for Tin (Sn) is 13.2°C.
- Hence, the correct answer is C, "13.2°C".
MCQs 10:
What is the transition temperature of KNO₃?
Topic: Transition Temperatures in Ionic Compounds
Correct Answer: C) 128.5°C
Detailed Hint:
- Just like in metals, the transition temperature in ionic compounds, such as KNO₃, is the temperature at which it can exist in two different crystalline forms in equilibrium.
- At this precise temperature, one crystalline form of the substance changes into another.
- The transition temperature for KNO₃ is 128.5°C.
- Thus, the correct answer is C, "128.5°C".
MCQs 11:
Which of the following is the smallest unit that represents the structure of an entire crystal?
Topic: The Smallest Unit of a Crystal Structure
Correct Answer: C) Unit cell
Detailed Hint:
- A crystal is a solid material whose constituents, such as atoms, molecules, or ions, are arranged in a highly ordered, repeating pattern extending in all three spatial dimensions.
- A unit cell is the smallest repeating unit of the lattice that, when stacked together, forms the entire crystal structure and inherits all the properties of the crystal.
- Hence, the correct answer is C, "Unit cell".
MCQs 12:
How would you best describe liquid crystals?
Topic: Characteristics of Liquid Crystals
Correct Answer: A) Always anisotropic
Detailed Hint:
- Liquid crystals are a state of matter that has properties between those of conventional liquids and those of solid crystals.
- While a crystalline solid may be either isotropic or anisotropic, liquid crystals are always anisotropic.
- This is because they display variations in their coefficient of thermal expansion.
- Therefore, the correct answer is A, "Always anisotropic".
MCQs 13:
What are the unit cell dimensions of a triclinic crystal?
Topic: Triclinic Crystal Unit Cell Dimensions
Correct Answer: C) a≠b≠c α≠β≠γ≠90°
Detailed Hint:
- The structure of a crystalline solid is defined by its unit cell, a small imaginary box containing one or more atoms which repeats infinitely in three dimensions to form the crystal.
- In triclinic crystals, the most general and least symmetric system, all three crystallographic axes of the unit cell (a, b, and c) and the three angles (α, β, γ) are unequal, and none of the angles is equal to 90°.
- Thus, the correct answer is C, "a≠b≠c α≠β≠γ≠90°".
MCQs 14:
Which of the following best describes Ice as a crystal?
Topic: The Nature of Ice Crystals
Correct Answer: B) Molecular
Detailed Hint:
- Crystals can be categorized based on the nature of the constituent units and the forces that hold them together.
- In a molecular crystal, such as ice, the constituent units are molecules which are held together by intermolecular forces.
- In the case of ice, the molecules are water molecules and the forces are hydrogen bonds.
- Therefore, the correct answer is B, "Molecular".
Question 15:
What is the structure of sodium chloride?
Topic: Structures of Ionic Crystals
Correct Answer: B) Face centered cube
Detailed Hint:
- Ionic compounds, such as sodium chloride (NaCl), form crystals with specific geometric arrangements.
- The structure of these crystals can be visualized as a unit cell, the smallest repeating unit in a crystal.
- NaCl has a cubic unit cell, specifically a face-centered cubic structure.
- Therefore, the correct answer is B, "Face centered cube".
Question 16:
Which characteristic allows Crystalline solids to be easily identified?
Topic: Identifying Crystalline Solids
Correct Answer: A) Sharp melting point
Detailed Hint:
- Crystalline solids possess a range of distinct characteristics owing to their highly ordered, repeating structural pattern.
- One distinguishing feature of crystalline solids is their sharp melting point, unlike amorphous solids that melt over a range of temperatures.
- Therefore, an effective way to identify a crystalline solid is by its sharp melting point.
- Hence, the correct answer is A, "Sharp melting point".
Question 17:
Which statement defines a malleable solid?
Topic: Malleability in Solids
Correct Answer: B) A solid that can be converted into thin sheets
Detailed Hint:
- Malleability is a property of metals which allows them to be molded into various shapes and sizes without breaking.
- When a solid is termed malleable, it implies that the substance can be hammered or rolled into thin sheets.
- This characteristic is predominantly found in metals, including zinc, as their atoms are arranged in a manner that allows them to slide past each other without breaking bonds.
- Thus, the correct answer is B, "A solid that can be converted into thin sheets".