A 25.0 g sample of an alloy was heated to 100.0 oC and dropped into a beaker containing 90 grams of water at 25.32 oC. The temperature of the water rose to a final value of 27.18 oC. Neglecting heat losses to the room and the heat capacity of the beaker itself, what is the specific heat of the alloy

Respuesta :

Answer:

The specific heat of the alloy [tex]C_{a} = 0.37 \frac{KJ}{Kg K}[/tex]

Explanation:

Mass of an alloy [tex]m_{a}[/tex] = 25 gm

Initial temperature [tex]T_{a}[/tex] = 100°c = 373 K

Mass of water [tex]m_{w}[/tex] = 90 gm

Initial temperature of water [tex]T_{w}[/tex] = 25.32 °c = 298.32 K

Final temperature [tex]T_{f}[/tex] = 27.18 °c = 300.18 K

From energy balance equation

Heat lost by alloy = Heat gain by water

[tex]m_{a}[/tex] [tex]C_{a}[/tex]  [[tex]T_{a}[/tex] - [tex]T_{f}[/tex]] = [tex]m_{w}[/tex] [tex]C_w[/tex] ([tex]T_{f}[/tex] -[tex]T_{w}[/tex] )

25 × [tex]C_{a}[/tex] × ( 373 - 300.18 ) = 90 × 4.2 (300.18 - 298.32)

[tex]C_{a} = 0.37 \frac{KJ}{Kg K}[/tex]

This is the specific heat of the alloy.

The specific heat capacity of the alloy is 0.385 J/gºC

We'll begin by calculating the heat absorbed by the water. This can be obtained as follow:

Mass of water (M) = 90 g

Initial temperature of water (T₁) = 25.32 °C

Final temperature (T₂) = 27.18 °C

Change in temperature (ΔT) = T₂ – T₁ = 27.18 – 25.32 = 1.86 °C

Specific heat capacity of water (C) = 4.184 J/gºC

Heat absorbed (Q) =?

Q = MCΔT

Q = 90 × 4.184 × 1.86

Q = 700.4016 J

Thus, the heat absorbed by the water is 700.4016 J

  • Finally, we shall determine the specific heat capacity of the alloy

Heat absorbed = Heat released

Heat absorbed = 700.4016 J

Heat released = –700.4016 J

Mass of alloy (M) = 25 g

Initial temperature of alloy (T₁) = 100 °C

Final temperature (T₂) = 27.18 °C

Change in temperature (ΔT) = T₂ – T₁ = 27.18 – 100 = –72.82 °C

Specific heat capacity of alloy (C) =?

Q = MCΔT

–700.4016 = 25 × C × –72.82

–700.4016 = –1820.5 × C

Divide both side by –1820.5

C = –700.4016 / –1820.5

C = 0.385 J/gºC

Therefore, the specific heat capacity of the alloy is 0.385 J/gºC

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