Calcium standard entropies

Hydrogen has been suggested as the fuel of the future. One way to store it is to convert it to a compound that can be heated to release the hydrogen. One such compound is calcium hydride, CaH2. This compound has a heat of formation of —186.2 kj/mol and a standard entropy of 42.0 J/mol-K. What is the minimum temperature to which calcium hydride would have to be heated to produce hydrogen at one atmosphere pressure ... 

PROBLEM 17.5 Calculate the standard entropy of reaction at 25°C for the decomposition of calcium carbonate ... 

Calcium carbonate (CaCOs) exists in two polymorphic forms, calcite and aragonite. The standard state enthalpy of calcite is -1207.37kJ/mol, while that of aragonite is —1207.74kJ/mol. The entropies of aragonite and calcite under the same conditions are 88Jmol" K" and 91.7 JmoL K, respectively. What is the stable polymorph at 25°C and 1 atm Is there a temperature above which the other polymorph would be the equilibrium phase If so, what is that T If not, why not ... 

Calcium carbonate is insoluble in water. Yef it dissolves in an acidic solution. Calculate the standard enthalpy, entropy, and Gibbs free energy change for the reaction between sohd calcium carbonate and hydrochloric acid. What drives the reaction, the enthalpy change, or the entropy change ... 

Both, enthalpy and entropy at standard conditions for chemical elements and compounds are tabularised [50], Using these values Jacquorie [261] calculated H and S at standard conditions for a sodium calcium silicate, a sodium borosilicate and a pure silica glass (Table 2.1). 

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