- #1

Magda|A380

- 5

- 0

## Homework Statement

0.2g of a radium salt was separated from a ton of uranium ore. The radioactive radium nuclide Ra-226 decays by alpha-particle emission with a half-life of 1600 years. 1 year = 3.16x10

^{7}s.

The curie is defined as the number of disintegrations per second from 1.0g of Ra.

Show that:

a)i) the decay constant of the radium nuclide is 1.4x10-11 s

^{-1}

ii) 1 curie equals 3.7x10

^{10}Bq

b) Show that the energy release in the decay of a single nucleus of Ra-226 by alpha-particle emission is 7.9x10

^{-13}J.

nuclear mass of Ra-226 = 226.0254u

nuclear mass of Rn-222 = 222.0175

nuclear mass of He = 4.0026u

c)

*Estimate the time it would take a freshly made sample of radium of mass 0.2g to increase in temperature by 1*

^{o}C. Assume that 80% of the energy of the alpha particles is absorbed within the sample so that this is the energy which is heating the sample. Take the specific heat capacity of radium to equal 110Jkg^{-1}K^{-1}. Use the data from a) and b)## Homework Equations

For a)i) I used λt

_{1/2 }= 0.693

For ii) I used A = λN (I used Avogadro's constant to find N of 1.0g of Ra-226.)

For b) I used E = Δmc

^{2}; 1u = 1.661x10

^{-27}kg

For c) E=mcΔT

## The Attempt at a Solution

Both part a) and b) were fine, but I'm having trouble with part c)

I was thinking of using E = mcΔT and having E = 0.8 x 7.9x10

^{-13}, m = 2x10

^{-4}kg, c=110; what value of ΔT should I be using? I thought it should be 1 because the temperature is being increased by 1

^{o}C? However, that doesn't fit the equation. Also, how can I find the time from this? Should I equate E to Qt or should I be using a different equation?

Sorry this is so long; I included parts a) and b) as they might be needed to work out part c).

Any help would really be appreciated.

Thanks