Calculate `DeltaH^(@)` for the reaction
`Na_(2)O(g)+SO_(3)(g)toNa_(2)SO_(4)(s)`
Given the following
`(i) Na(s)+H_(2)O(l)toNaOH(s)+(1)/(2)H_(2)(g)`, `DeltaH^(@)=-146 kJ`
`(ii) Na_(2)SO_(4)(s)+H_(2)O(l)to2NaOH(s)+SO_(3)(g)`, `DeltaH=+418 kJ`
`(iii) 2Na_(2)O(s)+2H_(2)(g)to4Na(s)+2H_(2)O(l)`, `DeltaH=+259kJ`

Options

A. `+823` kJ
B. `-581` kJ
C. `-435` kJ
D. `+531` kJ

Answer

B

Explanation

To obtain required result, Multiply eq. (i) by 2 & divide eq. (iii) by 2 and add both the eq. then subtract eq. (ii) from the sum.