The reaction `A to B` , `DeltaH=+24 kJ//"mole"`. For the reaction `B to C`, `DeltaH=-18 kJ//"mole"`. The decreasing order of enthalpy of `A`, `B`, `C` follow the order

Options

A. A,B,C
B. B,C,A
C. C,B,A
D. C,A,B

Answer

B

Explanation

`A rarr B, Delta H = +ve` means that `H (A) lt H(B)`
`B rarr C, DeltaH = -ve` means that `H(B) gt H(C ) ` or `H(C ) lt H(B)`
Adding the given equations,we get
`A rarrC, DeltaH = + 6 kJ mol^(-1)`. This means that `H(A) lt H(C )`
Combining the above results. `H(A) lt H (C ) lt H(B)` or `H( B) gt H( C) gt H(A)` . Hence, decreasing order of enthalpy is B,C,A.