DAT Question of the Day

Correct Answer: E. Pressure, volume and internal energy

The correct answer is E. The equation that governs enthalpy for a homogenous system (all gas or all liquid) is H = U + PV, where U is internal energy, P is pressure, and V is volume.

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Correct Answer: A. A 3D network lattice of covalently bonded carbon atoms.

Diamond is a 3D network lattice of covalently bonded carbon atoms, far right.

Graphite, another allotrope of carbon, is a 2D network lattice of covalently bonded carbon atoms, left.

A 3D network lattice of carbon ions held together by ionic bonds. Does not exist, as carbon does not form ions and elements cannot be ionic, only compounds can.

A 3D network lattice of carbon ions in a sea of mobile valence electrons held together by metallic bonds. This description is more metallic and similar to the description of graphite, which can conduct electricity, but not diamond.

A 3D network lattice of carbon atoms held together by hydrogen bonding and dispersion forces. Hydrogen bonding and dispersion forces are intermolecular forces, although dispersion forces are everywhere, but very weak.

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Correct Answer: C. nuclear decay

Nuclear decay involves the splitting of an unstable nucleus and emitting a radioactive particle. This process also decreases the energy of the original element. Nucleation though a chemistry term is related to the process of making a crystal from a supersaturated solution. A combustion reaction does generally result in the release of energy, but is not a mechanism used to make a nucleus more stable. Nuclear fusion is the process of adding elements together, increasing their energy, not decreasing their energy.

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Correct Answer: D. The gas is under low pressure and high temperature.

An ideal gas is a gas which obeys the Ideal Gas Laws. Real gases behave ideally when their particles are moving at high speed (high temperature)and there is lots of space between the particles (low pressure).The lower the temperature and higher the pressure the less ideal the gas behaves, especially as it approaches its liquidation point.

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