MCQ
When $ 4 \,g$ of iron is burnt to ferric oxide at constant pressure, $29.28\, kJ $ of heat is evolved. What is the enthalpy of formation of ferric oxide ......$kJ$ (At. Wt. of $Fe = 56$ )
- A$-81.98$
- ✓$-819.8 $
- C$-40.99$
- D$+ 819.8$
✓
Answer
Correct option: B.
$-819.8 $
(b)Given: Weight of iron burnt$ = 4\,g;$ Heat liberated $ = 29.28\,KJ$ and atomic weight of iron $(Fe) = 56$. We know that in ferric oxide $(F{e_2}{O_3}),\,2\,\,moles$ of iron or $2 \times 56 = 112\,gram$ of iron are burnt. We also know that when $4\,grams$ of iron are burnt, then heat liberated $= 29.28\, kJ, $ therefore when $112\,grams$ of the iron are burnt, then heat liberated $ = \frac{{29.28 \times 112}}{4} = - 819.8\,kJ$ (Minus sign due to liberation of heat).
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
$HI$ was heated in a closed tube at ${440\,^o}C$ till equilibrium is obtained. At this temperature $22\%$ of $HI$ was dissociated. The equilibrium constant for this dissociation will be
→Addition of a mineral acid to an olefin bond leads to major product, Identify it
If the $I.E.$ of $He^+$ us $54.4\,eV$ then -
→For the reaction : $N_2 (g)$ $+$ $3H_2(g)$ $\rightarrow$ $2NH_3(g)$, $\Delta H =\, -24\,Kcal$ at $427\,^oC$ and $200\,atm$ . Calculate magnitude of internal energy change (in $Kcal\,\Delta U$), if $168\,gm$ $N_2$ gas and $30 \,gm$ $H_2$ gas are allowed to react completely ( $100\%$ reaction yield) to form $NH_3$ gas at $427\,^oC$ and $200\,atm$......$Kcal$
→The colour of bromine solution is :
In the given bonds which one is most ionic
A gas present in a cylinder, expands against a constant pressure of $1\, atm$ from a volume of $2\, litre$ to a volume of $6\, litre$. In doing so, it absorbs $800\, joule$ heat from surrounding. The change in internal energy of process is.....$ joule$
→$IUPAC$ name of the compound $\mathop C\limits^4 {H_2} = \mathop C\limits^3 H - \mathop C\limits^2 {H_2} - \mathop C\limits^1 {H_2}OH$ is
→The order of dipole moments of the following molecules is
Hydrogenation of $2-$ Butyne in the presence of Lindlar's catalyst gives
→