CBSE Guess > Papers > Important Questions > Class XII > 2007 > Chemistry > Nuclear Chemistry

Nuclear Chemistry

Q. 1. H2+ 1 H3→ 2He4 + 0 n1 Calculate the energy released in (a)Mev/atom (b) Mev/mole (c)J/mole (d)J/atom
(e) J/g Given 1 H2=2.014 1 H3=3.016 2He4=4.003 0 n1 =1.009 (all in amu)

Q. 2. Mass defect of Cl35 is 0.320 amu. Calculate the binding energy/nucleon

Q. 3. 92U235+0n1 → 42 Mo98 + 54Xe136 + x −1eo +y0 n1 Find x and y and energy released per atom.

. 92U235=235.044 0 n1=1.009 Mo98=97.900 Xe136=135.907 (all in amu)

Q. 4. How many α and β particles are emitted in the reaction 90Th232 → 82Pb208

Q. 5. t½ of a radioactive element is 100seconds.Find λ How long will it take for 1g element to become 0.01g?

Q. 6. A radio active element decays in such a way that after 100 minutes ⅛th of the original amount remains.
Calculate t½ and λ.

Q. 7. Starting with 1g of a radio active element 0.25g is left after 5 days. Find the amount left after 1 day.

Q. 8. A piece of wood shows C14 activity which is 60% activity found today. Find the age of the sample.t½=5770years

Q. 9. t½ Hg 203=50 days. How much of 0.2g of sample left after 6 months.

Q. 10. A sample of pitch blend contains 0.05 gram Pb206 for every gram of U238. Find the age of the rock
t½ U238=4.5 x 109years.

Q. 11. A sample of pitch blend contain 5mg of U238 and 1.8mg of Pb208. Find the age of the rock. t½U238=4.5x109year

Q. 12. A piece of wood shows C14 activity 3.8 counts/minute/g of C. Determine the age of the wood if freshly cut wood shows an activity of 15.2 counts/minute/g of C. t½ of C14=5770years.

Q. 13. A rock contain U238 and Pb208 in the ratio 3:2. Find the age of the rock. t½U238=4.5x109year.

Q. 14. Complete the equation: (a) 7N14 (α,−) 8O17 (b) 13Al27 (α,n)……… (c) 25Mn55 (n, gamma)…….

(d) 96Cm246 + 6C12→ 102No254 + ……..

Q. 15. 84Po218 under goes an alpha emission followed by two beta emission. Find the position of the new element in the periodic table.

Q. 16. Calculate t½ for Am241. Given it emits 1.2 x 1011αparticles per gram per second.

Q. 17. The isotopic composition of Rb is Rb 85 = 72% and Rb 87 = 28%. Rb87 is weakly radio active and decay by β− emission with decay constant 1 x 10−11/year. A mineral pollucite contain 450milligram Rb and 0.72 mg Sr87. Find the age of the sample. Mention the assumptions made.

Q. 18. Calculate the mass of La140 in sample whose activity is 3.7 x 1010Bq. t½ La 140=40 hrs.

Q. 19. β−activity of CO2 prepared from a wood give 25.5 counts/minute. The same mass of CO2 from an ancient source gave 20.5 counts/minute. Find the age of the wood. What would be the expected count rate for an identical mass of CO2 from a sample which is 4000 years old.

Q. 20. During nuclear explosion, one of the product is Sr90 with t½ = 28 years. If 1 microgram of Sr90 was absorbed in the bones of a new born baby instead of calcium. How much of it will remain after 10 years.

Q. 21. During nuclear fission of U- 235 , 17.5 MeV of energy is generated per nucleus fissoned. Find the energy released in joules by fissioning 1gram of U-235.
( 1 Mev = 1.622x 10-13 J NA = 6.023X 1023 mol-1

Q. 22. 2NO+ O2→ 2NO2(g) How will the rate changes when the volume of the reaction vessel is reduced to one - thirds
(g) (g) of its original volume?