Atomic Decay and Heat capacity
9) 9. Calculate the decay constant of element Rn ,if during twenty four hours number of atoms decreases only to 18.2%?
1. $2.1*10^3 s^{-1}$
2. $2.1*10^{-5} s^{-1}$
3. $3.2*10^{-3} s^{-1}$
4. $2.1*10^6 s^{-1}$
5. $0.33*10^6 s^{-1}$
10) There are two samples with the same dimensions: copper and iron. Which molar heat capacity is smaller
1.copper
2. Iron
3. Equally
4. No correct answer
Answers
9) The decay constant L is defined as
$N(t)= N0*exp(-L*t)$
where N0 is the initial number of atoms and N(t) is the remaining number of atoms after time t
$N0/N = exp(L*t)$
$1/0.182 =exp(L*24*3600)$
$L* 86400 =1.704$
$L =1.97*10^{-5} sec =2*10^{-5} sec$
Correct answer is 2) $2*10^{-5} sec$
10) The molar heat capacity of copper is $C(Cu) =24.47 J/(mol*K)$ and the molar heat capacity of iron is $C(Fe) =25.1 J/(mol*K)$. Therefore copper has a smaller molar heat capacity.
Correct answer is 1. Copper