Romans used calcium oxide, CaO, to produce a strong mortar to build stone structures. Calcium oxide was mixed wit ch reacted slowly with CO2 in the air to give CaCO3. Ca(OH)2(s) +CO2(g) → CaCO3(s)+H20(g)

Required:
a. Calculate the standard enthalpy change for this reaction.
b. How much energy is evolved or absorbed as heat if 7.50 kg of Ca(OH)2 reacts with a stoichiometric amount of CO2.

The given reaction is:  

Ca(OH)₂ (s) + CO₂ (g) ⇒ CaCO₃ (s) + H₂O (g)

The ΔH°f of Ca(OH)₂ (s) is -986.09 kJ/mole, the ΔH°f of CO₂ (g) is -393.509 kJ/mol, the ΔH°f of CaCO₃ (s) is -1207.6 kJ/mol, and the ΔH°f of H₂O (g) is -241.83 kJ/mol.  

ΔH°rxn = 1 × ΔH°f of CaCO₃ (s) + 1 × ΔH°f of H₂O (g) - 1 × ΔH°f of Ca(OH)₂ (s) - 1 × ΔH°f of CO₂ (g)

ΔH°rxn = 1 (-1207.6) + 1(-241.83) - 1 (-986.09) - 1 (-393.509)

ΔH°rxn = -69.831 kJ

b) The molecular mass of calcium hydroxide is 74.096 gram per mole.  

The mass of calcium hydroxide given is 7.50 Kg or 7500 grams.  

The number of moles of calcium hydroxide is,  

n = Mass of Ca(OH)₂ / Molecular mass of Ca(OH)₂

n = 7500 / 74.1

n = 101.21 moles

As ΔH is negative, therefore, release of heat is taking place. Thus, when one mole of calcium hydroxide reacts, the heat released is -69.831 kJ. Therefore, 101.21 moles of calcium hydroxide will release the heat,  

= 101.21 × 69.831 kJ

= 7.067 × 10³ kJ

chemical energy is stored in the chemical bonds of atoms and molecules. it can only be seen when it is released in a chemical reaction. when chemical energy is released, the substance from which the energy came is often changed into an entirely different substance.

this chemical reaction releases energy in the form of light and heat. chemical energy is the potential energy stored in the arrangement of atoms within molecules. breaking chemical bonds requires energy, while forming new chemical bonds releases energy.

the atp molecule can store energy in the form of a high energy phosphate bond joining the terminal phosphate group to the rest of the molecule. in this form,energy can be stored at one location, then moved from one part of the cell to another, where it can be released to drive other biochemical reactions.

answer is: naturally occurring solid, inorganic compound or element is mineral.

minerals usually have crystalline form, that means than crystal constituents (atoms, molecules or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions.

for example magnetite is a mineral of iron oxide (fe₂o₃).

calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (caco₃).

dolomite is an   carbonate mineral composed of calcium magnesium carbonate (camg(co₃)₂).