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Example 6. Fossil dating Radioactive beryllium is sometimes used to date fossils found in deep-sea sediment. The amount of radioactive material x satisfies dx/dt = kx. Suppose that 10 units of beryllium are present in a living organism and that the half-life of beryllium is 4.6 million years. Find the age of a fossil if 20% of the original radioactivity is present when the fossil is discovered.

I need the answer quickly

Consider a radioactive nuclear decay series A → B → C → with decay constants AA, AB, AC..., and assume at time t = 0 only nuclei of type A are present. Now integrate your expression to find the number of nuclei of type B at time t, i.e. NB(t). [ Hint: multiply by et and use integration by parts. Don't forget the integration constant!] . In the case of the actinide series (e.g. half-life of 238 U is 4.47 x 10⁹ years, very much greater than the daughter nuclei!) show that the decay chain is in secular equilibrium, i.e. all the daughter nuclei have essentially equal activities.

3) You're wandering around and come upon an interesting looking rock. The rock is slightly radioactive, so you analyze it. The resulting data is as follows: Elapsed Time (s) Counts 962 50 891 100 718 150 598 200 531 250 448 300 413 350 334 400 308 450 287 500 202 550 178 600 154 a. Calculate the value of k using any two of the above data points. b. Use your value of k to determine the half-life of this sample.

TIme left 0:54 According to DLVO theory, the following is true except: Select one: O a. The flocculation or deflocculation of the particles depends on the sum of the two forces (attractive and repulsion). O b. If the repulsion forces are higher than the attractive forces the suspended particles will deflocculate. O c. Reducing the zeta potential will lead to reducing the attractive forces and deflocculation of the suspended particles O d. If the attractive forces are higher than the repulsion forces the suspended particles will flocculate. The followig are characteristics of solutions excent: ch

In fluorescence, the quantum yield is best defined as the:   A. number of photons emitted, divided by the number of photons absorbed.   B. rate of fluorescence emission.   C. fraction of excited molecules produced by direct excitation     D. number of photons emitted.

If the a and b loci are 16 mu apart in humans and an A B / a b woman marries an a b / a b  man.  What is the probability that their first child will be A b / a b?   0.08 0.16 0.32 0.84 0.64

Number 20 and 21 please

Scenario 3 At dinnertime, the soldiers we re miles from a fie ld kitchen. They each pulled out a meal pouch, inserted it into a small bag, and added water. Within 15 minutes, the soldiers were eating hot meals, which are the U.S. Army's "Meal, Ready-to-Eat," or MRE, Tatio Each MRE is a main dish within a pouch made of aluminum foil and plastic. In 1985, researchers at the Army's Natick Research, Development, and Engineering Center invented a way to heat MRES using a special "Flameless Ration Heater," or FRH. Each FRH is a plastic sleeve that holds a pad containing metal particles embedded in a polymeric matrix. The metal is an alloy of 90% magnesium and 10% iron. The entire package has a mass of 20.0 g, of which about 8.1 g is magnesium. In the FRH, the water reacts with magnesium in an exothermic reaction The energy released by this reaction warms the meal to 60°C. To speed the reaction, iron was added to the FRH. Both iron and magnesium react readily with warm water but since iron is…

Thank you. I'm just confused as what is is the reason 122.1 has to be multiplied by (-45543.23)?

2) Suppose that we have 100 cm' of water (p = 1g.cm"), which is D;0 in a proportion of %3! 0.015% (D stands for deuterium, or H). a) Compute the energy (in J) that would obtain from this sample if all the deuterium were to be consumed in the reaction H + H - 'H+p, which is known to release an energy output of 4.0 MeV. b) As an alternative, compute the energy (in J) that would be released if two-thirds of the deuterium were fused (according to the previous reaction) to form 'H, which then combines with the remaining one third according to the reaction H+ 'H → *He +n, known to release an energy output of 17.6 MeV. c) Which of the processes a) or b) produces more energy? Given: N = 6.022x10" mot P. ->

Which shows a correct match between the transition and lifetime? 3P -->1D   long lifetime 3S -->3P   long lifetime 1D -->1F   long lifetime 3P -->3D   long lifetime

The photochemical formation of molecule Z uses a radiation of 300 nm. The sample is irradiated with 100W of this radiation. The quantum yield is 0.2. If the sample absorbs only 50% of the radiation falling on it, then find the amount of Z formed in one second?