Question

Consider the following processes $△H\left(kJ/mol\right)$

$\frac{1}{2}A\to B+150$

$3B\Rightarrow 2C+D-125$

$E+A\to 2D+350$

For $B+D\to E+2C,△H$ will be:

• A. $+525kJ/mol$
• B. $-175kJ/mol$
• C. $-325kJ/mol$
• D. $+325kJ/mol$

Answer 1

The correct option is B $-175kJ/mol$

$\frac{1}{2}A\to B;△H=150kJ/mol...\left(i\right)$

$3B\to 2C+D;△H=+350kJ/mol....\left(ii\right)$

$E+A\to 2D;△H=+350kJ/mol...\left(iii\right)$

By $[2\times (i)+(ii\left)\right]-\left(iii\right)$, we get

$B+D\to E+2C$

$\therefore △H=150\times 2+(-125)-350$
$=-175kJ/mol$