You are Here: Home

# Particle physics question, pls help watch

1. can anyone help me with this question.

q) The fusion of deuterium nuclei can be represented by

2/1 H + 2/1 H = 4/2 He (top ones the mass and bottom is the atomic number)

a) calculate energy released by this reaction in joules given that:
mass of 2/1 H = 2.01419 u
mass of 4/2 He = 4.00277
1 u is equivalent to 1.49 x 10 ^-10 J

b) 2kg (1000 mol) of deuterium are caused to fuse and it is proposed that the energy released by fusion is used to generate electricity in a power station.
If the efficiency of the process were 52% and the electrical output of the station is to be 5.0 MW, how long would the deuterium last for?

thanks
2. (Original post by vp03)
can anyone help me with this question.

q) The fusion of deuterium nuclei can be represented by

2/1 H + 2/1 H = 4/2 He (top ones the mass and bottom is the atomic number)

a) calculate energy released by this reaction in joules given that:
mass of 2/1 H = 2.01419 u
mass of 4/2 He = 4.00277
1 u is equivalent to 1.49 x 10 ^-10 J

b) 2kg (1000 mol) of deuterium are caused to fuse and it is proposed that the energy released by fusion is used to generate electricity in a power station.
If the efficiency of the process were 52% and the electrical output of the station is to be 5.0 MW, how long would the deuterium last for?

thanks
a) E = (2*2.01419 - 4.00277)u = 3.82x10^-12 J

b) 1000mol deuterium = 500mol He formed

E/mol= E * 6.02x10^23 = 2.3x10^12 J mol^-1

= 1.15x10^15 J for 2kg deuterium at 100% efficieny
= 6.0x10^14 J at 52% efficiency

t=E/P = 1.2x10^8 s

Is this right?
3. yeh dats rite. but can u pls explain to me how u got that.
4. why did you go from 2.3 to 1.15 in b)??
5. a)

Because of E=mc^2, the mass of each particle can be given in terms of energy (ie - in terms of 'u'). When the two deuterium nuclei collide to create an alpha particle (4/2 He), the mass of the He is slightly less than the combined masses of the original nuclei. This mass is lost as it is released as energy. To calculate the size of this energy, you just find the difference between the energies (mass equivalent) of the product and reactants. ie - E = (2*2.01419u - 4.00277u) = 3.82x10^-12 J

b) This energy calculated above is for the formation of one helium nucleus. If 1000mol of deuterium nuclei are used, then 500mol of helium nuclei are created (equation: 2D --> 1He). Therefore, to calculate the energy released by this reaction, you multiply the energy of formation of one nucleus of He (from part a) by the number of nuclei formed (500moles= 500 * 6.02x10^23). This gives a value of E = 1.15x10^15 J. However, only 52% of this is converted to electrical energy so (0.52*1.15x10^15 = ) 6.0x10^14J of electrical energy is obtained.

If the power output is 5x10^6W and power is energy per unit time, then the time this energy will last = E/P = 1.2x10^8s.
6. tnx a lot bruv. really gr8ful for dat.

can u explain one last thing. y do u consider helium? i was doin it in terms of deuterium. tnx
7. The value calculated in part a) is the energy released when one helium nucleus is formed from two deuterium nuclei (energy of original deuterium nuclei - energy of helium nucleus formed).

So to calculate the total energy, you multiply a) (the energy when one helium nucleus is formed from two deuterium nuclei) by the number of helium nuclei formed.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: June 13, 2004
Today on TSR

Will it ever be possible?

### University open days

1. University of Cambridge
Wed, 26 Sep '18
2. Norwich University of the Arts
Fri, 28 Sep '18
3. Edge Hill University
Faculty of Health and Social Care Undergraduate
Sat, 29 Sep '18
Poll
Useful resources

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE