Heat Capacity and Specific Heat

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Physical Chemistry › Heat Capacity and Specific Heat

Questions 1 - 2

What is the specific heat capacity for a 50-gram sample of metal that increases in temperature by 10 degrees celsius when 2000 joules of energy is added?

$4\frac{J}{g^{\circ}C}$

$0.4\frac{J}{g^{\circ}C}$

$2.0\frac{J}{g^{\circ}C}$

$6.0\frac{J}{g^{\circ}C}$

Explanation

Use the equation:

$q=mC\Delta T$

We can calculate the specific heat capacity for the unknown metal. Since we know the added heat , the mass of the sample , and the change in temperature $\Delta T$ , we can solve for .

$C = \frac{q}{m\Delta T} = \frac{2000J}{(50g)(10^{\circ} C)} = 4.0\frac{J}{g^{\circ} C}$

A sample of an unknown metal at $100^\circ C$ is immersed in water and is allowed to reach equilibrium. If final temperature of the system is $25.1^\circ C$ and of energy are released, what is the identity of the metal?

Sp heat

It is impossible to determine

Explanation

Recall that the formula for specific heat is $q=mc\Delta T$ . Rearranging the equation for specific heat (c) yields $c=\frac{q}{m\Delta T}=\frac{-84J}{2.5g(-74.9^{\circ}C)}=0.449\frac{J}{{g\cdot ^{\circ}C}}$

Remark: keep in mind that the release of energy and the cooling of the metal will give negative values for both and $\Delta T$ .

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