Question

0.50 g of calcium chloride (CaCl2) was added to a test tube holding 5 mL of distilled water. A temperature probe was placed in the test tube to record any change in temperature during the reaction. The baseline temperature of the water before adding the CaCl2 was 23.6 degrees Celsius. After the CaCl2 was added to the water the temperature of the solution peaked at 25.7 degrees Celsius.

1) Draw an energy diagram of the process and label the Energy changes including the Enthalpy of solution.

2) Name the strongest attractive forces that exist in the solid (CaCl2) and the liquid (H2O). Will breaking these forces be Endothermic or Exothermic?

3) Name the attractive force (IPF) that is being created by the reaction. Is this step endothermic or exothermic?

4) Was the enthalpy of solution (the overall energy change) endothermic or exothermic?

Answer 1

Upon the addition of CaCl₂ in water, an increase in temperature was noted. This clearly implies exothermic nature of the reaction. In the reaction, the breaking of ions of CaCl₂ (Ca²⁺ and 2Cl^-) takes place and followed by the bond formation between ions and water molecules. The amount of energy is given back is greater in the formation of bond than the energy involved in the breaking of bonds between each Ca²⁺ ions and a pair of Cl^- ions.

CaCl₂(s) + H₂O -> Ca²⁺(aq) + Cl^-(aq)

1) Energy diagram of the process is exothermic as shown in the attached file.

Tansilion sta act Reach △H Pro

2) The strongest forces that exists in the solid CaCl₂ is ionic, and liquid H₂O is partially ionic in nature due to the presence of Oxygen. Breaking these forces will be exothermic in nature because heat is evolved in the reaction.

3)The attractive force being created by the reaction in ionic in nature.

4) The overall enthalpy of solution(the overall energy change) in exothermic in nature because the energy is evolved.