Join WhatsApp Icon JEE WhatsApp Group
Question 53

For the reaction $$H_2F_2(g) \rightarrow H_2(g) + F_2(g)$$
$$\Delta U = -59.6 \text{ kJ mol}^{-1}$$ at $$27°C$$
The enthalpy change for the above reaction is $$-$$ ______ $$\text{kJ mol}^{-1}$$ (nearest integer) (Given: $$R = 8.314 \text{ J K}^{-1} \text{ mol}^{-1}$$)


Correct Answer: 57

We are given: $$H_2F_2(g) \rightarrow H_2(g) + F_2(g)$$ and $$\Delta U = -59.6 \text{ kJ mol}^{-1}$$ at 27°C, and we need to find the enthalpy change $$\Delta H$$.

Since the relation between $$\Delta H$$ and $$\Delta U$$ is given by $$\Delta H = \Delta U + \Delta n_g RT$$, where $$\Delta n_g$$ is the change in the number of moles of gaseous products minus gaseous reactants, we proceed to determine $$\Delta n_g$$.

Substituting the stoichiometric coefficients shows that the moles of gaseous products are 1 ($$H_2$$) + 1 ($$F_2$$) = 2 and the moles of gaseous reactants are 1 ($$H_2F_2$$), which gives $$\Delta n_g = 2 - 1 = 1$$.

At 27°C (T = 300 K) and with R = 8.314 J K^{-1} mol^{-1}, we calculate $$\Delta n_g RT = 1 \times 8.314 \times 300 = 2494.2 \text{ J mol}^{-1} = 2.4942 \text{ kJ mol}^{-1}$$.

Therefore, $$\Delta H = \Delta U + \Delta n_g RT = -59.6 + 2.4942 = -57.1 \text{ kJ mol}^{-1}$$.

The question asks for the magnitude (with the negative sign already indicated): - ____ kJ mol$$^{-1}$$. Rounding to the nearest integer gives $$|\Delta H| \approx 57 \text{ kJ mol}^{-1}$$.

Therefore, the answer is 57.

Get AI Help

Video Solution

video

Create a FREE account and get:

  • Free JEE Mains Previous Papers PDF
  • Take JEE Mains paper tests

JEE Quant Questions | JEE Quantitative Ability

JEE DILR Questions | LRDI Questions For JEE

JEE Verbal Ability Questions | VARC Questions For JEE

Free JEE Topicwise Questions

JEE Rotational MotionJEE Units & MeasurementsJEE Atomic StructureJEE GravitationJEE Periodic Table & PeriodicityJEE StatisticsJEE Inverse Trigonometric FunctionsJEE Magnetism & Magnetic MaterialsJEE Sequences & SeriesJEE MatricesJEE Alternating CurrentsJEE Carboxylic AcidsJEE Permutations & CombinationsJEE Work, Energy & PowerJEE Electromagnetic InductionJEE Electronic DevicesJEE d and f-Block ElementsJEE Chemical KineticsJEE Heat TransferJEE Three Dimensional GeometryJEE Magnetic Effects of CurrentJEE Hydrocarbons - AromaticJEE Electromagnetic WavesJEE Aldehydes & KetonesJEE Hydrocarbons - AlkanesJEE Applications of DerivativesJEE EquilibriumJEE Indefinite IntegrationJEE Chemical ThermodynamicsJEE ElectrochemistryJEE ProbabilityJEE BiomoleculesJEE Continuity & DifferentiabilityJEE Kinetic Theory of GasesJEE Vector AlgebraJEE Hydrocarbons - AlkynesJEE Differential EquationsJEE Current & ResistanceJEE Straight LinesJEE WavesJEE Redox ReactionsJEE Hydrocarbons - AlkenesJEE DeterminantsJEE SolutionsJEE Ray OpticsJEE Dual Nature of Matter & RadiationJEE Chemical Bonding & Molecular StructureJEE Complex NumbersJEE Sets, Relations & FunctionsJEE Electric Charges & FieldsJEE Laws of MotionJEE Fluid MechanicsJEE Basic Concepts in ChemistryJEE Trigonometric FunctionsJEE LimitsJEE Laws of ThermodynamicsJEE Kinematics - 2D MotionJEE p-Block Elements (Groups 13-18)JEE Simple Harmonic MotionJEE Electric Potential & CapacitanceJEE Coordination CompoundsJEE JEE 2D GeometryJEE CirclesJEE Definite IntegrationJEE EMF & Circuit AnalysisJEE Surface TensionJEE Atoms & NucleiJEE Laboratory Experiments - XIJEE Number SystemJEE Basic Principles of Organic ChemistryJEE Wave OpticsJEE Quadratic EquationsJEE Alcohols, Phenols & EthersJEE Organic Compounds with HalogensJEE DifferentiationJEE Conic SectionsJEE Nitrogen-Containing CompoundsJEE ElasticityJEE Practical Organic ChemistryJEE Kinematics - 1D MotionJEE Purification & CharacterisationJEE Binomial Theorem
Ask AI