Advertisements
Advertisements
प्रश्न
The radionuclide 11C decays according to
\[\ce{^11_6C -> ^11_5B + e+ + \text{v}}\] : T1/2 = 20.3 min
The maximum energy of the emitted positron is 0.960 MeV.
Given the mass values: `"m"(""_6^11"C") = 11.011434 u and "m"(""_6^11"B") = 11.009305 "u"`
Calculate Q and compare it with the maximum energy of the positron emitted.
Advertisements
उत्तर
The given nuclear reaction is:
\[\ce{^11_6C -> ^11_5B + e+ + \text{v}}\]
Half life of `""_6^11C` nuclei `"T"_(1/2)` = 20.3 min
Atomic mass of `"m"(""_6^11"C")`= 11.011434 u
Atomic mass of `"m"(""_6^11"B") = 11.009305 "u"`
Maximum energy possessed by the emitted positron = 0.960 MeV
The change in the Q-value (ΔQ) of the nuclear masses of the `""_6^11"C"` nucleus is given as:
`triangle "Q" = ["m'"(""_6"C"^11) - ["m'"(""_5^11"B") + "m"_"e"]]"c"^2` ...(1)
Where,
me = Mass of an electron or positron = 0.000548 u
c = Speed of light
m’ = Respective nuclear masses
If atomic masses are used instead of nuclear masses, then we have to add 6 me in the case of `""^11"C"` and 5 me in the case of `""^11"B"`.
Hence, equation (1) reduces to:
`triangle"Q" = ["m"(""_6"C"^11) - "m"(""_5^11"B") - 2"m"]"c"^2` are the atomic masses
Here `"m"(""_6"C"^11) and "m'(""_5^11"B")` are the atomic masses
∴ Δ Q = [11.011434 − 11.009305 − 2 × 0.000548] c2
= (0.001033 c2) u
But 1 u = 931.5 Mev/c2
∴ Δ Q = 0.001033 × 931.5 ≈ 0.962 MeV
The value of Q is almost comparable to the maximum energy of the emitted positron.
संबंधित प्रश्न
Obtain the relation between the decay constant and half life of a radioactive sample.
A radioactive isotope has a half-life of T years. How long will it take the activity to reduce to a) 3.125%, b) 1% of its original value?
In a given sample, two radioisotopes, A and B, are initially present in the ration of 1 : 4. The half lives of A and B are respectively 100 years and 50 years. Find the time after which the amounts of A and B become equal.
The radioactive isotope D decays according to the sequence
If the mass number and atomic number of D2 are 176 and 71 respectively, what is (i) the mass number (ii) atomic number of D?
Lithium (Z = 3) has two stable isotopes 6Li and 7Li. When neutrons are bombarded on lithium sample, electrons and α-particles are ejected. Write down the nuclear process taking place.
When charcoal is prepared from a living tree, it shows a disintegration rate of 15.3 disintegrations of 14C per gram per minute. A sample from an ancient piece of charcoal shows 14C activity to be 12.3 disintegrations per gram per minute. How old is this sample? Half-life of 14C is 5730 y.
Define one Becquerel.
A radioactive substance disintegrates into two types of daughter nuclei, one type with disintegration constant λ1 and the other type with disintegration constant λ2 . Determine the half-life of the radioactive substance.
A source contains two species of phosphorous nuclei, \[\ce{_15^32P}\] (T1/2 = 14.3 d) and \[\ce{_15^33P}\] (T1/2 = 25.3 d). At time t = 0, 90% of the decays are from \[\ce{_15^32P}\]. How much time has to elapse for only 15% of the decays to be from \[\ce{_15^32P}\]?
Before the year 1900 the activity per unit mass of atmospheric carbon due to the presence of 14C averaged about 0.255 Bq per gram of carbon.
(a) What fraction of carbon atoms were 14C?
(b) An archaeological specimen containing 500 mg of carbon, shows 174 decays in one hour. What is the age of the specimen, assuming that its activity per unit mass of carbon when the specimen died was equal to the average value of the air? The half-life of 14C is 5730 years.
Two radioactive materials X1 and X2 have decay constants 10λ and λ respectively. If initially, they have the same number of nuclei, then the ratio of the number of nuclei of X1 to that of X2 will belie after a time.
A radioactive element disintegrates for an interval of time equal to its mean lifetime. The fraction that has disintegrated is ______
Two radioactive materials Y1 and Y2 have decay constants '5`lambda`' and `lambda` respectively. Initially they have same number of nuclei. After time 't', the ratio of number of nuclei of Y1 to that of Y2 is `1/"e"`, then 't' is equal to ______.
Two electrons are ejected in opposite directions from radioactive atoms in a sample of radioactive material. Let c denote the speed of light. Each electron has a speed of 0.67 c as measured by an observer in the laboratory. Their relative velocity is given by ______.
If 10% of a radioactive material decay in 5 days, then the amount of original material left after 20 days is approximately :
The half-life of the radioactive substance is 40 days. The substance will disintegrate completely in
When a nucleus in an atom undergoes a radioactive decay, the electronic energy levels of the atom ______.
Which sample, A or B shown in figure has shorter mean-life?
Consider a radioactive nucleus A which decays to a stable nucleus C through the following sequence:
A→B→C
Here B is an intermediate nuclei which is also radioactive. Considering that there are N0 atoms of A initially, plot the graph showing the variation of number of atoms of A and B versus time.
The radioactivity of an old sample of whisky due to tritium (half-life 12.5 years) was found to be only about 4% of that measured in a recently purchased bottle marked 10 years old. The age of a sample is ______ years.
