Understanding Matter: States and Structure

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Questions and Answers

Consider a sealed container with a mixture of ice, water, and water vapor at equilibrium. If the system is infinitesimally perturbed by decreasing the volume isothermally, which of the following best describes the immediate response according to Le Chatelier's principle and the Clapeyron equation?

The amount of ice will decrease, the amount of water will increase, and the vapor pressure will remain constant.
The amount of ice will increase, the amount of water will decrease, and the vapor pressure will remain constant. (correct)
The amount of ice will increase, the amount of water will decrease, and the vapor pressure will increase slightly.
The amount of ice will decrease, the amount of water will increase, and the vapor pressure will decrease slightly.

X-ray diffraction can be used to unequivocally determine the isotopic composition of a crystalline material without any prior knowledge of its elemental composition or crystal structure.

False (B)

Explain, using principles of quantum mechanics and atomic structure, why the first ionization energy of nitrogen is greater than that of oxygen, despite oxygen having a greater nuclear charge.

Nitrogen's electronic configuration ($1s^22s^22p^3$) has a half-filled p-orbital, conferring extra stability due to Hund's rule. Removing an electron from this stable configuration requires more energy than removing an electron from oxygen ($1s^22s^22p^4$), which does not have a half-filled or fully filled stable configuration. The increased stability outweighs the effect of the increased nuclear charge in oxygen.

In a system undergoing reversible adiabatic expansion, the change in ______ is zero, reflecting the absence of heat transfer.

entropy Signup and view all the answers

Match the following experimental techniques with the primary physical property they measure or probe:

Differential Scanning Calorimetry (DSC) = Heat flow Thermogravimetric Analysis (TGA) = Mass change Dynamic Mechanical Analysis (DMA) = Viscoelastic properties X-ray Photoelectron Spectroscopy (XPS) = Elemental composition and chemical states Signup and view all the answers

Consider a binary mixture of two ideal gases, A and B, with mole fractions $x_A$ and $x_B$, respectively, at a total pressure P and temperature T. Which of the following statements accurately describes the Gibbs free energy of mixing ($\Delta G_{mix}$)?

$\Delta G_{mix} = RT(x_A \ln x_A + x_B \ln x_B)$, and is always negative for ideal gases due to the increase in entropy. (C) Signup and view all the answers

The Debye model accurately predicts the heat capacity of all crystalline solids at all temperatures.

False (B) Signup and view all the answers

Explain how the concept of 'coordination number' influences the properties of both crystalline and amorphous materials, providing specific examples of how varying coordination number affects macroscopic behavior.

Coordination number (CN) dictates the number of nearest neighbors around an atom. In crystals, it affects packing efficiency, density, and mechanical strength; e.g., a higher CN in metals generally correlates with increased ductility and strength. In amorphous materials, variations in CN lead to structural disorder, influencing properties like glass transition temperature and viscosity; lower CN often results in a more open structure with reduced mechanical strength and a lower glass transition temperature. The size of the central atom and its neighbours will also affect the coordination number. Signup and view all the answers

According to Fick's first law of diffusion, the flux of atoms is proportional to the ______ of the concentration gradient and the diffusion coefficient.

negative Signup and view all the answers

Consider a scenario where a new element, 'Element X,' is discovered. Spectroscopic analysis reveals that its most abundant isotope, X-289, has an unusually small neutron absorption cross-section but exceptionally high alpha decay probability. Given this information, which of the following applications would be the MOST suitable and potentially revolutionary use for Element X?

As a targeted alpha therapy agent for treating highly localized and aggressive forms of cancer. (D) Signup and view all the answers

Flashcards

What is Matter?

Matter is anything that has mass and occupies space.

What are Elements?

Elements are pure substances consisting of only one type of atom, like gold (Au) or oxygen (O).

What are Compounds?

Compounds are substances formed from two or more different elements chemically bonded together, like water (H₂O).