nuclear chemistry.....aim 4

 what are fission and fusion nuclear reactions?

.....aim 3

home

aim 5.....

 

HW From textbook “CHEMISTRY a Contemporary Approach”

 

A fission nuclear reaction is the splitting of a heavy nucleus into two or more lighter nuclei.

Example

U-235 is bombarded with slow neutrons to produce Ba-139, Kr-94, or other isotopes and 3 fast moving neutrons

 

       

A nuclear chain reaction is a reaction in which an initial step, such as the reaction above, leads to a succession of repeating steps that continues indefinitely. Nuclear chain reactions are used in nuclear reactors and nuclear bombs.

Example

          

A fusion nuclear reaction  is the combination of very light nuclei to make a heavier nucleus. Extremely high temperatures and pressures are required in order to overcome the repulsive forces of two nuclei.

Example

 

       

 

       

 

       

Energy released in a nuclear reaction (fission or fusion) comes from the fractional amount of mass converted into energy. Nuclear changes convert matter into energy.  Energy released during nuclear reactions is much greater than the energy released during chemical reactions.

Example 

Consider the fusion nuclear reaction taking place in stars.

 

       

Mass of reactants = 4 (mass of H-1) = 4 (1.00718 amu) = 4.02872 amu

Mass of products = 1 (mass of He-4) = 1 (4.00150amu) = 4.00150 amu

 

The difference between the mass of the reactants and products is  4.02872 amu - 4.00150 amu or  0.02722 amu

 

This difference  is called the mass defect and it is converted into energy according  to the formula E = mc2

E = energy

m= mass

c = speed of light (3 x 108 m/s)

 

Since the speed of light is a large number a small mass change corresponds to a large amount of energy.

Problem

Given the information below calculate the mass defect for the following nuclear reaction.

Am-241 = 241.0047 amu

Np-237 = 236.9972 amu

He-4 = 4.0015 amu

 

           

TEST YOUR UNDERSTANDING

1/07

14 Given the diagram representing a reaction:

Which phrase best describes this type of reaction and the overall energy change that occurs?

        (1) nuclear, and energy is released (2) nuclear, and energy is absorbed (3) chemical, and energy is released (4) chemical, and energy is absorbed

6/07

29 Which balanced equation represents nuclear fusion?

30 The energy released by a nuclear reaction results primarily from the

        (1) breaking of bonds between atoms (2) formation of bonds between atoms (3) conversion of mass into energy (4) conversion of energy into mass

8/07

50 A nuclear fission reaction and a nuclear fusion reaction are similar because both reactions

        (1) form heavy nuclides from light nuclides (2) form light nuclides from heavy nuclides   (3) release a large amount of energy             (4) absorb a large amount of energy

1/06

25 The amount of energy released from a fission reaction is much greater than the energy released from a chemical reaction because in a

fission reaction

        (1) mass is converted into energy (2) energy is converted into mass (3) ionic bonds are broken (4) covalent bonds are broken

27 Types of nuclear reactions include fission, fusion, and

        (1) single replacement (2) neutralization (3) oxidation-reduction (4) transmutation

1/05

30 Which change takes place in a nuclear fusion reaction?

                (1) Matter is converted to energy. (2) Energy is converted to matter. (3) Ionic bonds are converted to covalent bonds. (4) Covalent bonds are converted to ionic bonds.

6/05

31 Which equation represents positron decay? 
32 Which equation represents a fusion reaction?

 

1/04

46 Nuclear fusion differs from nuclear fission because nuclear fusion reactions
        (1) form heavier isotopes from lighter isotopes (2) form lighter isotopes from heavier isotopes (3) convert mass to energy (4) convert energy to mass

6/04

32 In a nuclear fusion reaction, the mass of the products is
        (1) less than the mass of the reactants because some of the mass has been converted to energy     (2) less than the mass of the reactants because some of the energy has been converted to mass
        (3) more than the mass of the reactants because some of the mass has been converted to energy    (4) more than the mass of the reactants because some of the energy has been converted to mass

1/03 Given the nuclear equation:

a) State the type of nuclear reaction represented by the equation.

b) The sum of the masses of the products is slightly less than the sum of the masses of the reactants. Explain this loss of mass.

c) This process releases greater energy than an ordinary chemical reaction does. Name another type of nuclear reaction that releases greater energy than an ordinary chemical reaction.

8/02

 Given the fusion reaction:

home