loui665

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Calculate the minimum amount of energy, in joules ...

Calculate the minimum amount of energy, in joules, required to completely melt 145 g of silver initially at 16.0°C

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energy, silver, amount, calculate, minimum, completely, required, joules, °c, initially, melt

Posted 2008-12-01T02:08:45Z
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OronD

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Love is the battery of life....

Hi, --------- Srep I: Energy to bring the material to the melting point: Q1= m*C*(T1-T2) = 145*0.236*(962-16) = 32,372 Joules. Step II: Energy to melt it: Q2=m*L = 145*105= 15,225 Joules (L=Latent heat of Silver). So the energy needed is: Q=Q1+Q2= 32,372 + 15,225 = 47,597 Joules (or 48.6 Kilo Joules). ------------- Best regards,

Posted 2008-12-01T11:58:28Z

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EnergyFred

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Sustainable Energy for healthy grandchildren

I agree with the calculation by OronD but the answer could be refined by taking into account the increase in the value of the specific heat of Silver with increasing temperature as given by Compton's formula.

http://books.google.com/books?id=8ucDAAAAQAAJ&pg=PA307&lpg=PA307&dq=variation+of+silver+specific+heat+with+temperature&source=web&ots=AOLW3ILbXX&sig=6IeJqiHBfGQxafF0TK9BAlVjQO8&hl=en&sa=X&oi=book_result&resnum=13&ct=result#PPA307,M1

http://books.google.com/books?id=KvuQwf_xFhMC&pg=PA308&lpg=PA308&dq=Comptons+Formula+Specific+Heat&source=web&ots=gfYnEHKtpa&sig=KLy52K3_5MHRdcXc76OsJSCbcKQ&hl=en&sa=X&oi=book_result&resnum=4&ct=result

This google scanned reference shows a 10% increase in specific heat from .0557 at 0 C - 100 C to .0611 from 0C to 300 C (units are unspecified, but consistent with calories / gram) yielding .2329 J/(g degC) 0 - 100 C and .2555 J/(g deg C) 0 - 300 C

The Handbook of Chemistry and Physics specifies the specific heat of Ag as .235 J /deg K at 25 deg C

Thus the expected heat input required to heat the Silver to melting is at least 20% greater than expected by considering the specific heat to be constant. Also the final rounding of 47,597 J should be 47.6 KJoules.

regards,

Posted 2008-12-11T02:44:18Z

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EnergyFred was invited by Yedda to answer this question.

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Susan

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Hello,

Thank you for your info!

http://www.yachtshareware.com/blogger/earth4energy/
http://www.yachtshareware.com/blogger/home-made-energy/

Posted 2009-08-15T17:38:05Z

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