Question

For which one of the following reactions will delta H be approximately (or exactly) equal to delta E?

H2(g) + Br2(g) ---> 2HBr(g)
H2O(l) ---> H2O(g)
CaCO3(s) ---> CaO(s) + CO2(g)
2H(g) + O(g) ---> H2O(l)
CH4(g) + 2O2(g) ---> CO2(g) + 2H2O(l)

Answer 1

The sign of AS can be predicted for the process involving changes of state For example, AS>0(entropy increases)for the following conditions The phase transition from solid to liquid, solid to gas, liquid to gas. An increase in the number of moles of a gas during the chemical reaction gas productsreactarts The expression for theinternalenergyisasfollows Here,AH and ΔΕ will be essentially be equal when there! sno changein volume, that is Δび-0 (1)H2(g)+Br2 (8)2 HBr(g) Here, ASis0,so thereisnochangein volume Thus, Δ F-AE (2)H2o(l)H20(g) Here, ASisl,sothereissome changein volume Thus, Δ H# ΔΕ (3)CaCO, (s)>Cao(s)+CO2(g) Here, ASisl,sothereissome changein volume Thus, Δ H# ΔΕ (4)2H(g)+og)0() Here, ASis-3,sothereissome changein volume Thus,ΔΕ ΔΕ (5)CH4(g)+202(8)CO2(8)+2H2O() Here, ASis-2,sothereissomechangein volume Thus, Δ H ΔΕ