13. What is the symbol for Enthalpy change?

14. How do you measure Enthalpy Change?

15. What kind of reaction do you have when the Enthalpy change is negative?

13) symbol of enthalpy change = Δ H.

14) enthalpy change is nothing but heat absorbed or evolved.

During fusion enthalpy change

Δ H. = m Lf, m is mass and Ls is latent heat of fusion

During evaporation, enthalpy change

Δ H. = m Lv, m is mass and Lv is latent heat of evaporation

during temperature rise, enthalpy change

Δ H = m c Δ T

In case of gas, enthalpy change can be calculated by the following relation

Δ H = Δ E + W, Δ E is change in internal energy, W is work done by gas.

15) When enthalpy change is negative, that means heat is released to the environment. So reaction is called exothermic.

when heat is absorbed enthalpy change is positive. Reaction is endothermic.