Unlike chemical reactions, for which mass is conserved, nuclear reactions result

Question

Unlike chemical reactions, for which mass is conserved, nuclear reactions result in slight changes in mass. When mass is lost, it becomes energy according to the equation

E=mc2

where E is the energy in joules, m is the mass defect in kilograms, and c is the speed of light (c=3.00×108 m/s). The mass defect is the difference between the total mass of the products and the total mass of reactants. The following values can be used to calculate the mass defect.

Part A

The sun produces energy via fusion. One of the fusion reactions that occurs in the sun is

411H42He+201e

How much energy in joules is released by the fusion of 1.39 g of hydrogen-1?

Express your answer to three significant figures and include the appropriate units.

Explanation / Answer

now

dm = mass of reactants - mass of products

so

dm =( 4 x mass of 1H1) - mass of 4 He 2 - ( 2 x mass of 0 e -1 )

dm = ( 4 x 1.00782) - ( 4.00260) - ( 2 x 0.00054858)

dm = 0.02758284

this is for 4 moles of H reacted

now

moles of H = 1.39 / 1 = 1.39

4 moles of H ----> 0.02758284

1.39 moles of H ---> y

y = 0.02758284 x 1.39 / 4

y = 9.5850369 x 10-3

so

mass defect = 9.5850369 x 10-3 g

mass defect = 9.5850369 x 10-6 kg

now

dE = dm x c2

so

dE = 9.5850369 x 10-6 x ( 3 x 10^8)^2

dE = 8.6265 x 10^14 J

Related Questions

Navigate

• Browse (All)
• Browse U
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.