You visited us 1 times! Enjoying our articles? Unlock Full Access!

Byju's Answer

Standard XII

Chemistry

Heat of Formation

2.1 g of Fe...

Question

$2.1 g$ of $F e$ combines with $S$ evolving $3.77 k J$ . The heat of formation of $F e S$ in $k J / m o l$ is:

- 3.77

No worries! We‘ve got your back. Try BYJU‘S free classes today!

- 1.79

No worries! We‘ve got your back. Try BYJU‘S free classes today!

- 100.5

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses

None of these

No worries! We‘ve got your back. Try BYJU‘S free classes today!

Open in App

Solution

The correct option is B $- 100.5$
Molar mass of $F e = 56 g$

Given:-
Amount of heat evolved when $2.1 g$ of $F e$ reacts with $S = 3.77 k J$

Therefore,
Amount of heat evolved when $56 g$ of $F e$ reacts with $S = \frac{3.77}{2.1} \times 56 = 100.5 k J$

Hence the heat of formation of $F e S$ is $- 100.5 k J$ while $- v e$ sign indicates that the heat is evolved.

Suggest Corrections

Similar questions

Q. At

25^{o} C

, the following heats of formation are given:

Compound	${S O}_{2} (g)$	$H_{2} O (l)$
$Δ H_{f}^{o} (k J / m o l)$	$- 296.81$	$- 285.83$

For the reactions at

25^{o} C

2 H_{2} S (g) + F e (s) ⟶ F e S_{2} (s) + 2 H_{2}; Δ H^{o} = - 137 k J {m o l}^{- 1}

H_{2} S (g) + \frac{3}{2} O_{2} (g) + H_{2} O (l) + {S O}_{2} (g); Δ H^{o} = - 562 k J {m o l}^{- 1}

Calculate heats of formation of

H_{2} S (g)

and

F e S_{2} (s)

Q. From the data at

25^{o} C

{F e}_{2} O_{3} (s) + 3 C_{g r a p h i t e} ⟶ 2 F e (s) + 3 C O (g); Δ H^{o} = 492 k J / m o l

F e O (s) + C_{g r a p h i t e} ⟶ F e (s) + C O (g); Δ H^{o} = 155.8 k J / m o l

C_{g r a p h i t e} + O_{2} (g) ⟶ C O_{2} (g); Δ H^{o} = - 393.51 k J / m o l

C O (g) + \frac{1}{2} O_{2} (g) ⟶ C O_{2} (g); Δ H^{o} = - 282.98 k J / m o l

Calculate standard heats of formation of

F e O (s)

and

{F e}_{2} O_{3} (s)

Q. When

4 g

of iron is burnt to ferric oxide at constant pressure,

29.28 k J

of heat is evolved. What is the enthalpy of formation of the formation of ferric oxide? (Atomic Mass of

F e = 56 g / m o l e

)

Equal volumes of methanoic acid and sodium hydroxide are mixed. If $x$ kJ/mol is the heat of formation of water, the heat evolved (in kJ/mol) on neutralisation will be:

Q. Fe +S =Fes. Calculate the mass in g of iron sulphide formed when 28g of iron combines with 16g of sulphur.

Join BYJU'S Learning Program

2.1g of Fe combines with S evolving 3.77 kJ. The heat of formation of FeS in kJ/mol is:

$2.1 g$ of $F e$ combines with $S$ evolving $3.77 k J$ . The heat of formation of $F e S$ in $k J / m o l$ is: