He heat lost or gained by a system is related to its temperature change by a property called its heat capacity. The molar heat capacity of metals at or above room temperature equals 24.92 J K-1mol-1.

The temperature of a block of copper metal (molar mass 63.55 g mol-1) fell by 5.72 K when the copper block released 37.5 J of heat. What is the mass of the copper block?

The heat lost or gained by a system is related to its temperature change by a property called its heat capacity. The molar heat capacity of metals at or above room temperature equals 24.92 J K-1mol-1.

The temperature of a block of copper metal (molar mass 63.55 g mol-1) fell by 5.72 K when the copper block released 37.5 J of heat. What is the mass of the copper block?


You know that the heat capacity is 24.92 J K-1 mol-1

C_m = 24.92 \frac {J}{K\,mol}

You know the molecular mass (atomic weight) of copper. You can, therefore, divide C by that value to get a heat capacity in grams:

C_g = 24.92 \frac {J}{K\,mol} \, \div \, 63.55\,\frac {g}{mol} = ?? \, \frac {J}{K\, g}

Since you know the number of joules that were released, and the temperature rise, you can form an equation:

Cg = \frac {24.92\, J}{63.55 \, K\, g}= \frac {37.5 \, J} {5.72 \, K}

and solve for "g", the weight in grams.

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