CH4(g)+4Cl2(g) —>CCl4(l) + 4HCl(g) .Methane reacts with chlorine gas to produce
ID: 550489 • Letter: C
Question
CH4(g)+4Cl2(g) —>CCl4(l) + 4HCl(g)
.Methane reacts with chlorine gas to produce carbon tetrachloride and hydrogen chloride gas. Calculate the standerd entropy (d s) of the reaction and identify its spontaneity
2.calculate the standard molar enthalpy (delta H ) of the reaction
3.Explain if the reaction/process is always spontaneous,never spontaneous,or spontaneous only at high temperatures.(Hint: consider how delta H and deltaS influence delta G and spontaneity with the equation delta G =delta H -T deltaS )
Explanation / Answer
CH4(g)+4Cl2(g) —>CCl4(l) + 4HCl(g)
DHrxn = (DH0f,CCl4 + 4*DH0f,HCl)-(DH0f,CH4 + 4*DH0f,Cl2)
= (4*-92.31 + 1*(-135.4)) - (-74.8 + 4*0)
= -429.84 kj
Dsrxn = (S0f,CCl4 + 4*S0f,HCl)-(S0f,CH4 + 4*S0f,Cl2)
= (4*186.8 + 1*216.4)-( 186.2 + 4*223)
= -114.6 j/mol.k
DG = DH-TDS
from the formula, if DG atleast = o ,the process is spontaneous.
0 = (-429.84*10^3)-(T*-114.6)
T = temperature = 3750.8 k
the temperature below 3750.8 k,the process is spontaneous.(at that conditions DG = -ve)
as 3750.8 k = 3477.65 C, is high temperature
answer: spontaneous only at low temperatures.