The heat of combustion of yellow phosphorus and red phosphorus are -9.91 kJ/mol and -8.78 kJ/mol respectively. Then the heat of transition of yellow phosphorus to red phosphorus is

Options

A. `-18.69 kJ`
B. `+1.13 kJ`
C. `+18.69 kJ`
D. `-1.13 kJ`

Answer

D

Explanation

Aim : Yellow `P rarr "Red P" `
`2P_Y + 5/2 O_2 rarr P_2O_5,Delta H_1=- 9.91 kJ `
(ii) `2P_R= 5/2 O_2 rarr P_2O_5, Delta H_2 =-8.79 kJ `
Eq(i)-Eq(ii)
`Delta H =- 9.91 +8.79 =-1.13 kJ `