Advertisements
Advertisements
प्रश्न
In a periodic table the average atomic mass of magnesium is given as 24.312 u. The average value is based on their relative natural abundance on earth. The three isotopes and their masses are `""_12^24Mg` (23.98504u), `""_12^25 Mg` (24.98584u) and `""_12^26Mg` (25.98259u). The natural abundance of `""_12^24 Mg` is 78.99% by mass. Calculate the abundances of other two isotopes.
Advertisements
उत्तर
Average atomic mass of magnesium, m = 24.312 u
Mass of magnesium isotope `""_12^24 Mg`, m1 = 23.98504 u
Mass of magnesium isotope`""_12^25 Mg`, m2 = 24.98584 u
Mass of magnesium isotope `""_12^26 Mg`, m3 = 25.98259 u
Abundance of `""_12^24 Mg`, η1= 78.99%
Abundance of `""_12^25 Mg`, η2 = x%
Hence, abundance of `""_12^26 Mg`, η3 = 100 − x − 78.99% = (21.01 − x)%
We have the relation for the average atomic mass as:
`m = (m_1eta_1 + m_2eta_2 + m_3eta_3)/(eta_1 + eta_2 + eta_3)`
`24.312 = (23.98504 xx 78.99 + 24.98584 xx x + 25.98259 xx (21.01 - x))/100`
`2431.2 = 1894.5783096 + 24.98584x + 545.8942159 - 25.98259 x`
0.99675x = 9.2725255
:. x ~~ 9.3 %
And 21.01 - x = 11.71 %
Hence, the abundance of `""_12^25Mg` is 9.3% and that of `""_12^26 Mg` is 11.71%.
APPEARS IN
संबंधित प्रश्न
Two stable isotopes of lithium `""_3^6"Li"` and `""_3^7"Li"` have respective abundances of 7.5% and 92.5%. These isotopes have masses 6.01512 u and 7.01600 u, respectively. Find the atomic mass of lithium.
Boron has two stable isotopes, `""_5^10"B"` and `""_5^11"B"`. Their respective masses are 10.01294 u and 11.00931 u, and the atomic mass of boron is 10.811 u. Find the abundances of `""_5^10"B"` and `""_5^11"B"`.
The three stable isotopes of neon: `""_10^20"Ne"`, `""_10^21"Ne"` and `""_10^22"Ne"` have respective abundances of 90.51%, 0.27% and 9.22%. The atomic masses of the three isotopes are 19.99 u, 20.99 u and 21.99 u, respectively. Obtain the average atomic mass of neon.
The nucleus `""_10^23"Ne"` decays by `beta^(-)`emission. Write down the β decay equation and determine the maximum kinetic energy of the electrons emitted. Given that:
`"m"(""_10^23 "Ne")` = 22.994466 u
`"m"(""_11^23 "Na")` = 22.989770 u.
What do you mean by polar molecules and non-polar molecules? Give ‘one’ example each.
Show that the density of nucleus over a wide range of nuclei is constant-independent of mass number A.
Potassium-40 can decay in three modes. It can decay by β−-emission, B*-emission of electron capture. (a) Write the equations showing the end products. (b) Find the Q-values in each of the three cases. Atomic masses of `""_18^40Ar` , `""_19^40K` and `""_20^40Ca` are 39.9624 u, 39.9640 u and 39.9626 u respectively.
(Use Mass of proton mp = 1.007276 u, Mass of `""_1^1"H"` atom = 1.007825 u, Mass of neutron mn = 1.008665 u, Mass of electron = 0.0005486 u ≈ 511 keV/c2,1 u = 931 MeV/c2.)
Atomic mass unit (u) is defined as ________ of the mass of the carbon (12C) atom.
Nuclides with same neutron number N but different atomic number Z are called ______.
A nucleus of mass number A has a radius R such that ______.
A vessel contains oil (density 0.8 g/cm3) over mercury (density 13.6 g/cm3). A sphere of homogeneous composition floats with half its volume immersed in mercury and the other half in oil. The density of the material of the sphere in g/cm3 is ______.
The mass number of a nucleus is equal to the number of:-
Are the nucleons fundamental particles, or do they consist of still smaller parts? One way to find out is to probe a nucleon just as Rutherford probed an atom. What should be the kinetic energy of an electron for it to be able to probe a nucleon? Assume the diameter of a nucleon to be approximately 10–15 m.
Which of the following are the constituents of the nucleus?
Assertion (R): Fusion of hydrogen nuclei into helium nuclei is the source of energy of all stars.
Reason (R): In fusion heavier nuclei split to form lighter nuclei.
The volume occupied by an atom is greater than the volume of the nucleus by a factor of about:
