If a tree dies and the trunk remains undisturbed for 13,535 years, what percentage of original 14C/12C ratio is still present? (t1/2= 5730 years)

Use the following information to determine the activation energy for the reaction shown below. 2NO –> N2 + O2 Temperature (K) Rate Constant (L/mol·s) 1400 0.143 1500 0.693

An acid is a substance that produces OH – ions in water.

The rate constant for the beta decay of thorium-234 is 2.882 x 10–2 / day. What is the half-life of this nuclide?

For a particular chemical reaction ΔH = 5.8 kJ and ΔS = –23 J/K. Under what temperature condition is the reaction spontaneous?

Which gas has molecules with the greatest average molecular speed at 25°C? A) CH4 B) N2 C) CO2 D) Kr E) Ar

Which type of impression tray is pictured below?  

An impression is a positive reproduction of teeth and surrounding oral tissues.

What is the best material for an indirect inlay or onlay restoration if esthetics is a concern?

When there is a Primary key to Foreign key relationship between two tables, deleting a record from the Primary key table could leave an orphan record in the Foreign key table.