Podcast
Questions and Answers
What does the term 'decomposition' primarily refer to in chemistry?
What does the term 'decomposition' primarily refer to in chemistry?
- The breakdown of a substance into simpler components (correct)
- A method to enhance the stability of a compound
- The combination of different elements
- The formation of new compounds
In the context of molality, which of the following correctly describes the solute?
In the context of molality, which of the following correctly describes the solute?
- The total amount of solution
- The substance that is dissolved (correct)
- The substance that enhances the boiling point
- The solvent in which the solute is dissolved
What does the symbol 'Ea' typically represent in chemical kinetics?
What does the symbol 'Ea' typically represent in chemical kinetics?
- Activation energy (correct)
- Entropy of reaction
- Energy of formation
- Electronegativity
What is the significance of the Arrhenius equation in chemistry?
What is the significance of the Arrhenius equation in chemistry?
In a solution, which component is considered the solvent?
In a solution, which component is considered the solvent?
Flashcards
Arrhenius Equation
Arrhenius Equation
The Arrhenius equation relates the rate constant of a reaction (k) to the activation energy (Ea) and temperature (T). It expresses the exponential dependence of the rate constant on temperature and the relationship between the activation energy and the rate constant: k = A*exp(-Ea/RT), where A is the pre-exponential factor, R is the ideal gas constant, and T is the absolute temperature.
Activation Energy (Ea)
Activation Energy (Ea)
The activation energy of a chemical reaction is the minimum amount of energy that must be provided for the reaction to occur. It represents the energy barrier that reactants need to overcome before they can transform into products.
Pre-exponential Factor (A)
Pre-exponential Factor (A)
The pre-exponential factor (A) in the Arrhenius equation reflects the frequency of collisions between molecules with proper orientation for a reaction to occur. A higher pre-exponential factor indicates more frequent collisions, leading to a faster rate constant.
Rate Constant (k)
Rate Constant (k)
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Ideal Gas Constant (R)
Ideal Gas Constant (R)
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Study Notes
Part E - Chemical Kinetics
- Rate constant for hydrocarbon decomposition at 50°C is 2.418 x 10⁻⁵ s⁻¹.
- Activation energy is 179.9 kJ/mol.
- Pre-exponential factor calculation using Arrhenius equation: log k = log A - (Ea / 2.303RT)
- Calculating log A, the result is 12.592
- Pre-exponential factor (A) = 3.90 x 10⁷⁵
Part E - Solution Chemistry - Molecular Weight Calculation
- 2.5 g of a non-volatile substance 'X' is dissolved in 100g of water.
- The rate constant for the reaction is determined.
- Mole fraction of the solute (X) = 0.0385
- Given mass of the solute (X) = 2.5 g
- Mass of the solvent (water) = 100 g
- Calculate the molecular weight of the solute 'X'.
- Mole fraction of the solute = moles of solute / (moles of solute + moles of solvent)
- Moles of solvent = mass of solvent / molar mass of solvent = 100 g / 18 g/mol = 5.56 moles
- Mole fraction of solute = 0.0385 = moles of solute / (moles of solute + 5.56 moles)
- Solve for moles of solute = 0.21466 and using molecular weight of solute and moles of the solute to calculate molecular weight of the solute = 11.1979 g/mol.
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