## CORE INFORMATION\n✓ **Answer**: B\n## CONCEPT FRAMEWORK\n\t**Primary Concept**: Density and relative density of gases\n\t**Related Topics**: Molecular weight, ideal gas law\n\t**Prerequisites**: Understanding of density and how it relates to mass and volume.\n## SOLUTION PATHWAY\n**Given Information**:\n\tThe question asks about the relative density of hydrogen gas compared to air.\n**Method & Steps**:\n\t1. Determine the molar mass of hydrogen ($H_2$) and the average molar mass of air.\n\t\tReasoning: Density is directly proportional to molar mass for gases at the same temperature and pressure. Air is a mixture of gases, primarily nitrogen ($N_2$) and oxygen ($O_2$).\n\t\tFormula/Rule: Density ($\rho$) is proportional to molar mass ($M$) at constant temperature and pressure: $\rho \propto M$\n\t2. Compare the molar masses.\n\t\tWorking: Molar mass of $H_2$ = 2 g/mol. Average molar mass of air is approximately 29 g/mol (considering the composition of air).\n\t\tKey Point: Since hydrogen has a much lower molar mass than air, it will have a lower density.\n\t3. Conclude on the relative density.\n\t\tResult: Hydrogen gas is lighter than air.\n\t\tVerification: The result aligns with the known properties of hydrogen. It's the lightest element and therefore its gas form is less dense than air.\n## OPTION ANALYSIS\nA :x: Heavier than air is incorrect because hydrogen's molar mass is significantly lower than air's.\nB ✓: Lighter than air is correct due to hydrogen's lower molar mass and hence lower density.\nC :x: The same density as air is incorrect; their molar masses differ significantly.\nD :x: A liquid at room temperature is incorrect; hydrogen is a gas at room temperature.\n## LEARNING AIDS\n\t**Common Mistakes**:\n\t\t1. Confusing density with mass: Remember that density is mass per unit volume. Hydrogen has a low mass, but also a low volume (per mole), resulting in a low density.\n\t\t2. Neglecting the composition of air: Air is not a single gas; considering its average molar mass is crucial for comparison.\n\t**Quick Tips**:\n\t\t1. Remember that lighter gases rise and heavier gases sink in air.\n\t\t2. Use the periodic table to quickly estimate the molar mass of elements and simple compounds.

The correct Option is "Lighter than air"

NEET Chemistry Hydrogen Hydrogen MCQs

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NEET Questions / Chemistry / Hydrogen / Hydrogen

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A metal hydride crystallizes in a face-centered cubic lattice with hydrogen atoms occupying tetrahedral voids. If the edge length of the unit cell is 'a', what is the distance between two nearest hydrogen atoms?

a/2

a/√2

a/4

√3a/4