A 44.0 g sample of an unknown metal at 99.0 oC was placed in a constant-pressure calorimeter of negligible heat capacity containing 80.0 mL water at 24.0 oC. The final temperature of the system was found to be 28.4 oC. Calculate the Specific heat of the metal if density of water is 1.00 g/ml.

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Answer:

[tex]C_m=0.474\frac{J}{g\°C}[/tex]

Explanation:

Hello.

In this case, since this is a system in which the water is heated up and the metal is cooled down in a calorimeter which is not affected by the heat lose-gain process, we can infer that the heat lost by the metal is gained be water, it means that we can write:

[tex]Q_m=-Q_w[/tex]

Thus, in terms of masses, specific heats and temperatures we can write:

[tex]m_mC_m(T_{eq}-T_m)=-m_wC_w(T_{eq}-T_w)[/tex]

Whereas the equilibrium temperature is the given final temperature of 28.4 °C and we can compute the specific heat of the metal as shown below:

[tex]C_m=\frac{-m_wC_w(T_{eq}-T_w)}{m_m(T_{eq}-T_m)}[/tex]

Plugging the values in and since the density of water is 1.00 g/mL so the mass is 80.0g, we obtain:

[tex]C_m=\frac{-80.0g*4.184\frac{J}{g\°C} (28.4\°C-24.0\°C)}{44.0g(28.4\°C-99.0\°C)}\\\\C_m=0.474\frac{J}{g\°C}[/tex]

Best regards!

The specific heat capacity of the metal is 0.474 J/gºC

We'll begin by calculating the mass of the water.

Density = 1 g/mL

Volume = 80 mL

Mass =?

Mass = Density × Volume

Mass of water = 1 × 80

Mass of water = 80 g

  • Next, we shall determine the heat gained by the water.

Mass of water (M) = 80 g

Initial temperature of water (T₁) = 24 °C

Final temperature (T₂) = 28.4 °C

Change in temperature (ΔT) = T₂ – T₁ = 28.4 – 24 = 4.4 °C

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

Heat gained (Q) =?

Q = MCΔT

Q = 80 × 4.184 × 4.4

Q = 1472.768 J

  • Finally, we shall determine the specific heat capacity of the metal.

Heat gained = 1472.768 J

Heat lost = –1472.768 J

Mass of water (M) = 44 g

Initial temperature of water (T₁) = 99 °C

Final temperature (T₂) = 28.4 °C

Change in temperature (ΔT) = T₂ – T₁ = 28.4 – 99 = –70.6 °C

Specific heat capacity of metal (C) =?

Q = MCΔT

–1472.768 = 44 × C × –70.6

–1472.768 = –3106.4 × C

Divide both side by –3106.4

C = –1472.768 / –3106.4

C = 0.474 J/gºC

Therefore, the specific heat capacity of the metal is 0.47 J/gºC

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