Question

Find the enthalpy of reaction,
$2HC\equiv CH+5O_2\to 4C{O}_2+2H_{2}O$
If the bond energies of $C-H,C\equiv C,O=O,C=O$ and $O-H$ bonds are $p,q,r,s,t$ respectively

• A. $[8s+4t]-[4p+2q+5r]$
• B. $[4p+2q+5r]-[8s+4t]$
• C. $[4p+2q+5r-8s+4t]$
• D. $[2p+q+5r]-[8s+4t]$

Answer 1

The correct option is A $[8s+4t]-[4p+2q+5r]$

For,

$2HC\equiv CH+5O_2\to 4C{O}_2+2H_{2}O$

Bond energy of $2HC\equiv CH=(2p+q)\times 2=4p+2q$

Bond energy of $5O_2=5\times r$

Bond energy of $4C{O}_2=8\times s$

Bond energy of $2H_{2}O=4\times t$

Enthalpy of the reaction = Bond energy of products - Bond energies of reactants = $8s+4t-5r-4p-2q$