Question

3. A molten metal of mass 150 g is kept at its melting
point 800°C. When it is allowed to freeze at the
same temperature, it gives out 75,000 J of heat
energy
(a) What is the specific latent heat of the metal ?
(b) If the specific heat capacity of metal is
200 J kg-1 K-1, how much additional heat
energy will the metal give out in cooling to
- 50 °C ?​

Answer 1

Answer:

Explanation:

Let L be the latent specific heat of the metal.

When the metal is allowed to be solidified its mp i.e. 800  

∘

C, it will give out latent heat only.

mL=75000

0.150×L=75000

L=500000Jkg  

−1

 

​  

 

Now,

Heat given out by the metal in cooling down to −50  

∘

C. Fall in temperature will be 800  

∘

C−(−50  

∘

C)=850  

∘

C

Heat given out= m×s×t=(0.150×200×850)=25500J

Answer 2

$\huge\underline\bold{AnSweR}$

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a)Mass of metal=>150g

Latent heat of metal=

mL=75000

0.150×L=75000

$L=500000Jkg^{-1}$

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b)Heat capacity of metal is 200$Jkg^{-1}K^{-1}$

Change in temperature =800-(-50)=850°C(or 850K)

∴ Heat given out

=m×s×t

=(0.150 x 200 x 850) J

= 25500 joule.

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