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Ch.5 - Thermochemistry
Brown - Chemistry: The Central Science 15th Edition
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoBrown 15th EditionCh.5 - ThermochemistryProblema 121b
Capitolo 5, Problema 121b

At 20 °C (approximately room temperature) the average velocity of N2 molecules in air is 1050 mph. (b) What is the kinetic energy (in J) of an N2 molecule moving at this speed?

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Convert the velocity of the N2 molecule from miles per hour (mph) to meters per second (m/s) using the conversion factor: 1 mph = 0.44704 m/s.
Calculate the mass of an N2 molecule. The molecular weight of N2 is approximately 28 g/mol. Convert this mass to kilograms (kg) by using the conversion factor: 1 g = 0.001 kg. Then, use Avogadro's number (6.022 \(\times\) 10^{23} molecules/mol) to find the mass of one molecule.
Use the kinetic energy formula: KE = \(\frac{1}{2}\)mv^2, where 'm' is the mass of the molecule in kg and 'v' is the velocity in m/s.
Plug the values of 'm' and 'v' into the kinetic energy formula to calculate the kinetic energy of the N2 molecule.
Ensure the final kinetic energy value is in Joules (J), as this is the standard unit for energy in the International System of Units (SI).

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Concetti chiave

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Kinetic Energy

Kinetic energy is the energy possessed by an object due to its motion, calculated using the formula KE = 0.5 * m * v², where m is the mass of the object and v is its velocity. For gas molecules like N₂, this concept is crucial for understanding how speed translates into energy at the molecular level.
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Kinetic & Potential Energy

Molecular Mass

The molecular mass of a substance is the mass of a single molecule, typically expressed in atomic mass units (amu). For nitrogen (N₂), the molecular mass is approximately 28 amu, which is essential for calculating the kinetic energy of an individual N₂ molecule when given its velocity.
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Atomic Mass

Conversion of Units

In physics and chemistry, it is often necessary to convert units to ensure consistency in calculations. In this case, converting the speed from miles per hour (mph) to meters per second (m/s) is essential for using standard SI units in the kinetic energy formula, allowing for accurate energy calculations.
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Conversion Factors
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