The half-life for the radioactive decay of U-238 is 4.5 billion years and is independent of initial concentration. If a sample of U-238 initially contained 3.2⨉1018 atoms when the universe was formed 13.8 billion years ago, how many U-238 atoms does it contain today?
The diagram shows the energy of a reaction as the reaction progresses. Label each blank box in the diagram.
a. reactants b. products c. activation energy (Ea) d. enthalpy of reaction (ΔHrxn)


Verified Solution

Key Concepts
Reactants and Products
Activation Energy (Eₐ)
Enthalpy of Reaction (ΔH₍rxn₎)
The half-life for the radioactive decay of C-14 is 5715 years and is independent of the initial concentration. How long does it take for 25.00% of the C-14 atoms in a sample of C-14 to decay?
The half-life for the radioactive decay of C-14 is 5715 years and is independent of the initial concentration. If a sample of C-14 initially contains 1.5 mmol of C-14, how many millimoles are left after 2725 years?
The activation energy of a reaction is 44.2 kJ/mol and the frequency factor is 1.9⨉1011/ s. Calculate the rate constant of the reaction at 25 °C.
The rate constant (k) for a reaction was measured as a function of temperature. A plot of ln k versus 1/T (in K) is linear and has a slope of -7012 K. Calculate the activation energy for the reaction.
The data shown here were collected for the first-order reaction: N2O(g) → N2(g) + O(g) Use an Arrhenius plot to determine the activation barrier and frequency factor for the reaction.
Temperature (K) Rate Constant (1 , s)
800 3.24⨉10- 5
900 0.00214
1000 0.0614
1100 0.955