Strontium-90 is a radioactive material that decays according to the function \( A(t)=A_{0} e^{-0.0244 t} \), where \( A_{0} \) is the inifial amount present and \( A \) is the amount present at time \( t \) (in years). Assume that a scientist has a sample of 800 grams of strontium- 90 . (a) What is the decay rate of strontium- 90 ? (b) How much strontium- 90 is left after 40 years? (c) When will only 200 grams of strontium- 90 be left? (d) What is the halt-life of strontium- 90 ?

If the half-life of I-131 is 10.4 days, how many moles of I-131 would be left in Mr. Miller's body after 47 days if he was infused with 7.2 grams? (Round your answer to four decimal places)

Relacione la simbologia, con los tipos de reacciones químicas. \( \begin{array}{ll}A B \rightarrow A+B \\ A+B C & A C+B \\ A+B & \text { Elegir... } \\ A B & \\ A B & \text { Descomposición }\end{array} \)

Question 1 Use the following scenario for questions 1 through 4: Dr. Goodie wants to treat Mr. Miller's thyroid cancer by using Radioactive lodine (RAI) treatment after an unsuccessful surgery to remove the cancer. Dr. Goodie explains that this treatment consists of injecting radioactive iodine (I- 131) into the bloodstream. Since the thyroid is the only place the body stores iodine, it is a relatively safe way to destroy cancer cells within the thyroid. Dr. Goodie apologetically leaves to deal with an emergent issue, but Mr. Miller still has some concerns. Answer the following to alleviate Mr. Miller's concerns: Dr. Goodie estimates Mr. Miller will need to be infused with approximately 7 grams of I-131 over a 3-hour period of time to reach a sufficient therapeutic level of radiation. How many grams of iodine-131 would remain in Mr. Miller's body after 6.5 half-lives? (Round your answers to two decimal places)

2. Find \( \Delta \mathrm{H}^{\circ} \) for the reaction \( 2 \mathrm{H}_{2}(\mathrm{~g})+2 \mathrm{C}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(\mathrm{l}) \), using the following thermochemical data. \( \begin{array}{ll}\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(\mathrm{l})+2 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow 2 \mathrm{CO}_{2}(\mathrm{~g})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) & \Delta \mathrm{H}=-875 \mathrm{~kJ} \\ \mathrm{C}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{CO}_{2}(\mathrm{~g}) & \Delta \mathrm{H}=-394.51 \mathrm{~kJ} \\ \mathrm{H}_{2}(\mathrm{~g})+1 / 2 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) & \Delta \mathrm{H}=-285.8 \mathrm{~kJ}\end{array} \)

If the half-life of I-131 is 7.4 days, how many days would it take for only \( 3.2 \times \) \( 10^{-2} \) grams of \( 1-131 \) to be left in Mr. Miller's body if Dr. Goodie started him on an initial dose of 5.5 grams?