The half-life of Radium- 226 is 1590 years. If a sample contains 500 mg , how many mg will remain after 3000 years?

Which of the following represent a buffer system? Check all that apply. \( \square \mathrm{NaOH} \) and NaCl \( \square \mathrm{H}_{2} \mathrm{CO}_{3} \) and \( \mathrm{NaHCO}_{3} \) HF and KF KCl and NaCl

\[ \mathrm{Fe}_{2} \mathrm{O}_{3}(\mathrm{~s})+2 \mathrm{Al}(\mathrm{s}) \rightleftharpoons \mathrm{Al}_{2} \mathrm{O}_{3}(\mathrm{~s})+2 \mathrm{Fe}(\mathrm{s}) \] View Available Hint(s) The equilibrium will shift toward the reactants. The equilibrium will shift toward the products. The reaction will not shift toward either the products or reactants. The reaction will shift toward both the reactants and products.

The pH scale for acidity is defined by \[ \mathrm{pH}=-\log \left[\mathrm{H}^{+}\right] \] where \( \left[\mathrm{H}^{+}\right] \)is the concentration of hydrogen ions measured in moles per liter (M). a) A sample of rhubarb is found to have a hydrogen concentration of 0.000501 M . What is the pH? Round your answer to 2 decimal places. \( \mathrm{pH}=\square \) b) The pH of a sample of red onion is 5.40 . What is the hydrogen concentration? Keep at leost 2 non-zero decimal ploces. \( \left[\mathrm{H}^{*}\right]=\square \)

Based on your worksheet results, please match the following: The electron group geometry of NH 3 is The electron group geometry of BF 3 is [Choose ] The electron group geometry of \( \mathrm{PF5} \) is [Choose ] [Choose ] electron group geometry of SF4 is geometry of PF 3 is [Choose ]

Which of the following molecule(s) have lone pair electrons and/or non-identical central bonds? \( \mathrm{CCl}_{4} \) \( \mathrm{CHCl}_{3} \) \( \mathrm{SO}_{3} \) \( \mathrm{CO}_{2} \mathrm{O} \)