How would you know whether a reaction is nuclear or chemical when an atom underg

Question

How would you know whether a reaction is nuclear or chemical when an atom undergoes a reaction and attains a more stable form. Give more than one reason. Uranium-234 is used to make dental crowns appear brighter. What isotope is produced by he alpha decay of Uranium-234? Write the balanced nuclear equation. Thorium-230 can be used to provide coloring in glass objects. One method of producing Thorium-230 is through the radioactive decay of Actinium-230. Write the nuclear reaction and determine the type of decay and whether neutron-proton ratio will increase or decrease? a-The half life of Tritium (^3_1H) is 12.3 y. If 48 mg of tritium is released from a nuclear power plant, what mass of the nuclide will remain after 49.2 y? After 98.4 y?

Explanation / Answer

II- Nuclear reactions are accompanied by elementary particles like alpha, beta, positrons, neutrons etc along with gamma radiation. The chemical reactions are basically the rearrangement of the electrons in the outer most shell with bonding involving either ionic or covalent bonds. Nuclear reactions involves the use of partice acclerators or use of neutrons (from a reactor or a source like Cf-252).

a)92U234 --------> 90Th230 + 2He4 (Alpha decay reaction, Change in mass and atomic number)

b) 38Sr85 ------------>37Rb85 + (electron capture) (Change in atomic number, no change in mass number)

c) 89Ac230 ------------->90Th230 + (Beta decay)(Change in atomic number, no change in mass number)

Calculation of n/p ratio

89Ac230 : no of neutrons : 141 ; no of protons: 89; n/p = 1.584

90Th230 : no of neutrons : 140 ; no of protons: 90; n/p = 1.555

There is a decrease in n/p ratio in the above nuclear transfomation.

III

t1/2 = 12.3 years (Half life of tritium)

N0 = 48 mg (Initial Sample)

N =? (after time, t)

N= N0e- t (First order radioactive decay equation)

= 0.639/12.3 = 0.056 y-1

t = 49.2 years

N = 48e-(0.056x49.2) = 48e-(2.755) = 48*0.0623 = 2.99 mg

So the sample of tritium remaining after 49.2 years is 2.99 mg

After 98.4 years

N = 48e-(0.056x98.4) = 48e-(5.510) = 48*0.00404 = 0.194 mg

So the sample of tritium remaining after 98.4 years is 0.194 mg

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