Question

When $Zn$ dust is added to sufficiently large volume of aqueous solution of copper sulphate. $3.175$ g of copper metal and $20$ J of heat is evolved. The $\Delta H$ for the reaction is:
$Zn\left(s\right)+CuS{O}_4\left(aq\right)⟶ZnS{O}_4\left(aq\right)+Cu\left(s\right)$
(Atomic weight of $Zn=65.3$, atomic weight of $Cu=63.5$)

• A. $20J$
• B. $200J$
• C. $400J$
• D. $65.3J$

Answer 1

The correct option is C $400J$

$COS{O}_4+Z_n\to CO+ZnS{O}_4$

mass of $Co\left(m\right)=3.175g$ Molecular $\left(M\right)=63.55$

no. of moles of $Co\left(O\right)=\frac{m}{M}=\frac{3.175}{63.55}=0.04996mol$

$\therefore 0.04996$ mol & $Co=20z$

So, 1 mol of $CO=\frac{20}{0.04996}=400.32J$