Define briefly why quartz SiO2(s) is much harder than dry ice CO2(s) although the very similar formula.
Compute oxide spontaneously absorbs water vapor from the atmosphere at 20 degrees Celsius via the following reaction CaO(s) + H2O(g) arrow Ca(OH)2(s)
Based on this information forecast the signs (+ and -) for the entropy change as well as for the enthalpy change in this reaction explain your reasoning briefly