Calcium hydroxide, which reacts with carbon dioxide to form calcium carbonate, was used by the ancient romans as mortar in stone structures. the reaction for this process is ca(oh)2(s) + co2(g) → caco3(s) + h2o(g) δh = –69.1 kj what is the enthalpy change if 3.8 mol of calcium carbonate is formed?

-262.58 kJ

Explanation:

The enthalpy represents the energy that is either absorbed or released during a chemical reaction.  

We see that the chemical reaction that we have is balanced and 1 mol of calcium carbonate was formed. During this process -69.1 kJ or energy was released because it has a negative sign. We can say that the enthalpy changes  is -69.1kJ per every mol of calcium carbonate formed.  

Using a simple rule of three we can get the enthalpy change when 3.8 mol of are formed.

-69.1 Kj --- > 1 mol of  

X         --- >  3.8 mol of

So, the energy released when 3.8 mol of calcium carbonate are formed is -262.58 kJ.  

pure substance: iron,copper

impure substance: water,charcoal

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.