
At 1 bar and , standard molar enthalpy of formation of which substance is zero?
A)
B)
C)
D)All correct
Answer
139.8k+ views
1 likes
Hint:To solve this question, it is required to have knowledge about standard enthalpy of formation of any substance. The standard molar enthalpy of formation of a compound is defined as the enthalpy of formation of 1 mole of pure compound in its stable state at normal room temperature and pressure. At the normal temperature and pressure of the compound given, it is zero.
Complete step by step answer:
As we know that, 1 bar pressure and a temperature of are regarded as normal room temperature and pressure. So, we shall check each option for the correct answer:
In option A, the phase given is gaseous phase. We know that, in the gaseous phase at room temperature, hydrogen is present as . It is present as di-hydrogen has and not mono-hydrogen gas . So, the molar enthalpy of formation is not zero.
In option B, the phase given is aqueous phase. We know that any polar compound containing hydrogen simultaneously dissociates into hydrogen ion and its conjugate base. Thus, is normal at room temperature. So, the standard molar enthalpy of formation is zero.
In option C, the phase given is gaseous. We know that, in gaseous phase hydrogen exists as di-hydrogen gas and not in its ionic form. It is present as and not . So, the standard molar enthalpy of formation is not zero.
Option D is not the correct option as well because option A and option C are incorrect.
The correct option is option B, i.e. at 1 bar and has a standard molar enthalpy of formation of zero.
Note: If the substance if present in a particular state at that phase, pressure and temperature, it is said that the standard molar enthalpy of formation of that compound is zero. For example, the molar enthalpy of formation of water in gaseous phase at 373 K will be zero. But for water in the liquid phase, the enthalpy of formation will be zero ay 298 K.
Complete step by step answer:
As we know that, 1 bar pressure and a temperature of
In option A, the phase given is gaseous phase. We know that, in the gaseous phase at room temperature, hydrogen is present as
In option B, the phase given is aqueous phase. We know that any polar compound containing hydrogen simultaneously dissociates into hydrogen ion and its conjugate base. Thus,
In option C, the phase given is gaseous. We know that, in gaseous phase hydrogen exists as di-hydrogen gas and not in its ionic form. It is present as
Option D is not the correct option as well because option A and option C are incorrect.
Note: If the substance if present in a particular state at that phase, pressure and temperature, it is said that the standard molar enthalpy of formation of that compound is zero. For example, the molar enthalpy of formation of water in gaseous phase at 373 K will be zero. But for water in the liquid phase, the enthalpy of formation will be zero ay 298 K.
Latest Vedantu courses for you
Grade 11 Science PCM | CBSE | SCHOOL | English
CBSE (2025-26)
School Full course for CBSE students
₹41,848 per year
EMI starts from ₹3,487.34 per month
Recently Updated Pages
JEE Main Participating Colleges 2024 - A Complete List of Top Colleges

JEE Main Maths Paper Pattern 2025 – Marking, Sections & Tips

Sign up for JEE Main 2025 Live Classes - Vedantu

JEE Main 2025 Helpline Numbers - Center Contact, Phone Number, Address

JEE Main Course 2025 - Important Updates and Details

JEE Main 2025 Session 2 Form Correction (Closed) – What Can Be Edited

Trending doubts
JEE Main 2025 Session 2: Application Form (Out), Exam Dates (Released), Eligibility, & More

JEE Main 2025: Derivation of Equation of Trajectory in Physics

JEE Main Exam Marking Scheme: Detailed Breakdown of Marks and Negative Marking

Learn About Angle Of Deviation In Prism: JEE Main Physics 2025

Number of sigma and pi bonds in C2 molecule isare A class 11 chemistry JEE_Main

Electric Field Due to Uniformly Charged Ring for JEE Main 2025 - Formula and Derivation

Other Pages
NCERT Solutions for Class 11 Chemistry Chapter 9 Hydrocarbons

NCERT Solutions for Class 11 Chemistry Chapter 7 Redox Reaction

JEE Advanced Marks vs Ranks 2025: Understanding Category-wise Qualifying Marks and Previous Year Cut-offs

NCERT Solutions for Class 11 Chemistry Chapter 5 Thermodynamics

Hydrocarbons Class 11 Notes: CBSE Chemistry Chapter 9

NCERT Solutions for Class 11 Chemistry In Hindi Chapter 1 Some Basic Concepts of Chemistry
