•Question 8 (1 point) How much energy is
produced when the sun converts
1 kg of hydrogen into helium? Note that this is different than a problem which asks how much energy is produced
when the sun converts 1
kg of mass into energy. When hydrogen is converted to helium, only a small fraction of the
mass is "lost" and converted
to energy.
a. 1.2 x 1012 J b. 6.4 x 1014 J
c. 2.8 x 1015 J
d. 9.0 x 1016 J
•From
class notes: Compare
mass of four 1H
to mass of one 4He
–6.693 ´ 10-27 kg - 6.645 ´ 10-27 kg = 0.048 ´ 10-27 kg drop in
mass
–E =
mc2 = 0.048 ´ 10-27 kg ´ (3 ´ 108 m/s)2 = 0.43 ´ 10-11 kg m2/s2 =
0.43 ´ 10-11 J
–So
4.3 ´ 10-12 J of energy released for
every He made.
–How many Hydrogen atoms in a kg? Just 1 kg/1.673x10-27 = 5.976x1026
–Divide this by 4 (since 4 hydrogens = 1
He). Multiply this by energy for each He produced = 5.976x1026 x 4.3 ´ 10-12 J = 6.4 x 1014 J