Chapter 3: Problem 60
What is the ratio of kinetic energies of \(3 \mathrm{~g}\) of hydrogen and 4 grams of oxygen at \(\mathrm{T}(\mathrm{K})\) ? (a) \(12: 1\) (b) \(6: 1\) (c) \(1: 6\) (d) \(24: 1\)
Short Answer
Expert verified
The ratio of kinetic energies of hydrogen and oxygen is 12:1.
Step by step solution
01
Understand Kinetic Energy Formula
The kinetic energy of gas molecules at a particular temperature can be given by the formula \( KE = \frac{3}{2} k T \), where \( k \) is the Boltzmann constant and \( T \) is the temperature in Kelvin. However, here we're dealing with moles of gas, so we use molar kinetic energy as \( KE = \frac{3}{2} RT \), where \( R \) is the universal gas constant.
02
Calculate Moles of Gases
First, we need to calculate the moles of hydrogen and oxygen. The molar mass of hydrogen is approximately \(2 \mathrm{~g}/\mathrm{mol}\) and for oxygen is \(32 \mathrm{~g}/\mathrm{mol}\). Thus, moles of hydrogen = \( \frac{3}{2} = 1.5 \) moles, and moles of oxygen = \( \frac{4}{32} = 0.125 \) moles.
03
Calculate Kinetic Energy for Each Gas
Since the kinetic energy per mole for any ideal gas at a given temperature \( T \) is the same, total kinetic energy for a gas is given by \( KE = n \times \frac{3}{2} RT \). Therefore, kinetic energy for hydrogen is \( KE_H = 1.5 \times \frac{3}{2} RT \) and for oxygen is \( KE_O = 0.125 \times \frac{3}{2} RT \).
04
Ratio of Kinetic Energies
Now, we find the ratio of kinetic energies: \( \text{Ratio} = \frac{KE_H}{KE_O} = \frac{1.5 \times \frac{3}{2} RT}{0.125 \times \frac{3}{2} RT} = \frac{1.5}{0.125} \). Calculate this ratio to get \( \frac{1.5}{0.125} = 12 \).
05
Conclusion
The ratio of kinetic energies of the hydrogen to oxygen is therefore 12:1. Compare it with the given options.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Ideal Gas Law
The ideal gas law is a fundamental equation in chemistry and physics that relates four key properties of gases: pressure, volume, temperature, and the number of moles. The formula is expressed as:\[ PV = nRT \]where:
- P is the pressure of the gas
- V is the volume of the gas
- n is the number of moles of gas
- R is the universal gas constant \(8.314 \, \text{J/(mol K)}\)
- T is the temperature in Kelvin
Moles Calculation
Calculating the moles of a substance is crucial for understanding how much of a compound or element is present in a given sample.Moles are calculated using the formula:\[ n = \frac{m}{M} \]where:
- \( n \) is the number of moles
- \( m \) is the mass of the substance in grams
- \( M \) is the molar mass of the substance in \( \text{g/mol} \)
Molar Mass
Molar mass is a key concept in chemistry that is used to convert between the mass of a substance and the number of moles. The molar mass is the mass of one mole of a given substance, typically expressed in grams per mole (\(\text{g/mol}\)). It is calculated by summing the atomic masses of all atoms in a molecule of the substance, as provided on the periodic table.For instance:
- Hydrogen (H2) has a molar mass of approximately \(2 \, \text{g/mol}\) since the atomic mass of a single hydrogen atom is \(1 \, \text{u}\).
- Oxygen (O2) has a molar mass of approximately \(32 \, \text{g/mol}\) because the atomic mass of a single oxygen atom is \(16 \, \text{u}\).