10. [A4] Actinium-225 is a radioactive metallic element. A container that initially had 400 grams of Actinium- 225 has 40 grams remaining after 31 days. Determine the half-life of Actinium-225. Keep answers as exact values using common logarithms. 11. [A2] Orange juice has a hydrogen ion concentration of 0.001 mol/L. What is its pH? PH = - log[H+] 12. [A3] The 2011 Tohoku earthquake off the coast of Japan measured a magnitude of 9.1 on the Richter scale and caused over $360 billion USD of damage. In contrast, the 2014 earthquake in Thailand measured 6.1 on the Richter scale. How many times more intense was the Japan earthquake than the Thailand earthquake? M2 - M1 = log ?)