Heat of combustion ΔH for C(s) , H₂(g)and CH₄(g) are -94, -68 and -213 kcal/mol.

⇦

⇨

Heat of combustion ΔH for C(s) , H₂(g)and CH₄(g) are -94, -68 and -213 kcal/mol. Then ΔH for C(s) + 2H₂(g) → CH₄(g)is

Options

(a) -17 kcal
(b) -111kcal
(c) -170 kcal
(d) -85 kcal

Correct Answer:

-17 kcal

Explanation:

(i) C(s) + O₂ = CO₂ ; ΔH(i) = -94 kcal/mol,
(ii) 2H₂ + O₂ = 2H₂O ; ΔH(ii) = -68 x 2 kcal/mol,
(iii) CH₄ + 2O₂ = CO₂ + 2H₂O ; ΔH(iii) = -213 kcal/mol,
(iv) C(s) + 2H₂(g) = CH₄(g) ; ΔH(iv) = ?,
By applying Hess’s law we can compute ΔH(iv), (i) + (ii) – (iii), we have
C + O₂ + 2H₂ + O₂ – CH₄ – 2O₂ = CO₂ + 2H₂ O – CO₂ – 2H₂ O,
C+ 2H₂ = CH₄,
Therefore ΔH(iv) = ΔH(i) + ΔH(ii) – ΔH(iii) = (-94 – 68 x 2 + 213 ) kcal = -17 kcal.

Related Questions:

1. The total number of isomeric alcohols with the molecular formula C₄H₉OH is
2. According to IUPAC nomenclature sodium nitroprusside is named as
3. Vapour density of a metal chloride is 77. If its equivalent weight is 3, its atomic
4. Antiferomagnetic substances possess
5. Which of the following statements about amorphous solids is incorrect

Topics: Thermodynamics (179)
Subject: Chemistry (2512)

---

Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score

18000+ students are using NEETLab to improve their score. What about you?

Solve Previous Year MCQs, Mock Tests, Topicwise Practice Tests, Identify Weak Topics, Formula Flash cards and much more is available in NEETLab Android App to improve your NEET score.

---

Share this page with your friends