Which nuclear equations is properly balanced? Uranium-234 undergoes spontaneous

Question

Which nuclear equations is properly balanced? Uranium-234 undergoes spontaneous radioactive decay to give an alpha particle and a new nucleus, X. What is x? _90^230Th _90^230U _94^238U _94^238Pu In the nuclear reaction what is X? proton neutron deuteron electrons positron If it takes 5.0 years for^60Co to lose one-half of its radioactivity, what percentage of its original activity will remain at the end of 20 years? 0% 6.25% 12.5% 25.0% In the nuclear reactions the element Z that is formed is _90^239Z _90^240Z _90^238Z _93^239Z _94^239Z A sample of a radioactive isotope initially contains 20 times 10^10 atoms. After 16 days, 5 times 10^10 atoms remain. What is the half-life of the isotope? 4days 8days 12days 16days A contain radioactive isotope has a half size of 10mins. If we have 20 mu g of this isotope at one instant, have many micro protons will remain at the end of 20 minutes? 0 2.5 5 10 20 beta nucleus may lead to increased nuclear visibility by decreasing the n/p ratio. Increasing the mass number. decreasing the mass number. decreasing the atomic number. which particle, if local from the nuclear, will result is no change in the atomic number? proton newton alpha particle beta particle non of these Rank the 3 types of radioactivity from leave to mass pending. alpha

Explanation / Answer

A balanced nuclear reaction is one where , the sum of atomic numbers as well as mass numbers of reactants should be equal to sum of atomic numbers and mass numbers of products. Accordingly,

3.

The decay of radioactive elements is 1st order. The rate constant (K) and half life (t1/2)are related as

K= 0.693/t1/2, K= 0.693/10 =0.0693/min

For 1st order reaction, lnM= lnMo-kt, M= mass at any time, t=20 minutes and Mo= 20ug

lnM= ln(20)-20*0.0693

M= 5 ug ( So C is correct)

4. beta rays are positrons or electrons emitted. During beta emission, a neutron is converted to proton.

n ( neutron)---->P( proton)+e-( eletrons) + eletron anti neutrino

So n/p ratio decreases. since P increases.

5.

6. Loonger wave length refer to less penetration and shorter wave length means more penetration. Accordingly, Y> Beta>Alpha. or alpha<beta<Y. So b is correct.

7. Alpha is   Helimum nuclues and hence can be stopped by any material. Hence D is correct.

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