Question

Evaluate $w$ at $500K$ for the process
$Mg\left(s\right)+2HCl\left(g\right)=MgC{l}_2\left(s\right)+H_2\left(g\right);$ when $2$ moles of $HCl\left(g\right)$ react completely at $1$ atm pressure throughout.
(The volume change of solids to be ignored)

• A. $-4.2kJ$
• B. $4.2kJ$
• C. $-8.4kJ$
• D. $8.4kJ$

Answer 1

The correct option is B $4.2kJ$

$2Mg+2HCl⟶MgC{l}_2\left(s\right)+H_2\left(g\right)$

2 Mole of HCL gas react with 1mol magnesium to produce 2mole hydrogen gas

$pressure=1atm$ $Temp=500K$

$Volume=\frac{nRT}{P}=\frac{1\times 0.821\times 500}{1atm}=41.05litre$

Work done $△W=P△V$

$=1atm\times 41.05=1.03125\times {10}^5\times 41.05\times {15}^{-3}joule$

$=42.33\times {10}^{2}joule$

$=4.2KJ$