NCERT Class XII Chapter
Nuclei
Questions With Solutions
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Question : 12
Total: 31
Find the Q-value and the kinetic energy of the emitted α-particle in the α-decay of (a)
R a
R n
Given m(
R a ) (
R n )
m(
R n ) (
P o )
m α
Given m
m
Solution:
(a) α-decay of
R a
R a
R n +
H e + Q
so, Q value
Q =[ m (
R a ) − m (
R n ) − m (
H e ) ] c 2
Q = [226.02540 – 222.01750 – 4.00260] × 931.5 MeV
Q = 0.0053 × 931.5 MeV = 4.937 MeV
Kinetic energy of emitted α-particle
K α
K α
K α
(b) α-decay of
R n
R n
P o +
H e + Q
Q =[ m (
R n ) − m (
P o ) − m (
H e ) ] c 2
Q = [220.01137 – 216.00189 – 4.00260] 931.5 MeV = 6.41 MeV
Kinetic energy of emitted α particle
K α
so, Q value
Q =
Q = [226.02540 – 222.01750 – 4.00260] × 931.5 MeV
Q = 0.0053 × 931.5 MeV = 4.937 MeV
Kinetic energy of emitted α-particle
(b) α-decay of
Q =
Q = [220.01137 – 216.00189 – 4.00260] 931.5 MeV = 6.41 MeV
Kinetic energy of emitted α particle
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