Determine whether each of the following statements about the thermodynamic funct

Question

Determine whether each of the following statements about the thermodynamic functions are True or False as they apply to chemical reactions. _____The heat of reaction at constant pressure is always equal to the work done by the reaction. _____Enthalpy and temperature are multiplied in the Gibbs free energy. _____All spontaneous chemical reactions have no heat of reaction. _____Negative entropy changes increase spontaneity. _____Spontaneity is increased by negative enthalpy changes.

Explanation / Answer

this is a bit haphazard answer but it is complete...i hope this will help you... the heat of reaction at constant pressure is always equal to the work done by the reaction. The heat of reaction at constant pressure is always equal to the change in the enthalpy. - This is correct. From the first law, ?E = q - w, where ?E is the change in internal energy of a system, q is the heat energy added to the system from the surroundings, and w is the work done by the system on the surroundings. For mechanical work, w = p?V, so ?E = q - p?V. The definition of the enthalpy is H = E + pV or ?H = ?E + V?p + p?V. Rearranging this last equation, we get: ?E = ?H - V?p - p?V. Now equate ?E between this expression and the one from the first law: ?H - V?p - p?V = q - p?V ?H - V?p = q but for a constant-pressure process, ?p = 0, so: ?H = q All spontaneous chemical reactions have positive heats of reaction. -- This is false. If T?S > ?H, then ?H can be positive, but the Gibbs free energy change will still be negative. Spontaneity is increased by negative enthalpy changes. in order words we can say that Spontaneity is decreased by positive enthalpy changes.-- This is false. A process that has a positive enthalpy change absorbs thermal energy (it's endothermic). This works against spontaneity. Entropy and enthalpy are included in the Gibbs free energy. -- This is true. One definition of the Gibbs free energy is: ?G = ?H - T*?S,where H is the enthalpy and S is the entropy. Spontaneity is increased by negative enthalpy changes. false Spontaneity is decreased by negative entropy changes. -- This is true. A condition for spontaneity of a process at constant temperature and pressure is that ?G = ?H - T?S < 0 T is always positive (it is measured in kelvins), so if ?S is negative, the entropy term makes ?G larger, which is in the opposite direction for promoting spontaneity

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