Question

A sample of substance X that has a mass of 326. 0 g releases 4325. 8 cal when it freezes at its freezing point. If substance X has a molar mass of 58. 45 g/mol, what is the molar heat of fusion for substance X? Use q equals n delta H. 13. 31 cal/mol 74. 00 cal/mol 775. 6 cal/mol 19054. 7 cal/mol.

Answer 1

The molar heat of fusion of X has been 775.6 cal/mol. Thus, option C is correct.

The molar heat of fusion has been defined as the energy absorbed or released by a mole of substance in converting between solid and liquid state.

Computation for the molar heat of fusion

The given mass of substance X has been, 326 g.

The molar mass of substance X has been 58.45 g/mol.

The moles of sample have been given as:

$\rm Moles=\dfrac{Mass}{Molar\;mass}\\\\ Moles\;X=\dfrac{326\;g}{58.45\;g/mol}\\\\ Moles\;X=5.58\;mol$

Thus, the amount of heat absorbed by 5.58 mol of sample has been 4325.8 cal.

The amount of heat absorbed by a mole of sample has been:

$\rm 5.58\;mol=4325.8\;cal\\\\1\;mol=\dfrac{4325.8\;cal}{5.58\mol} \\\\1\;mol=775.6\;cal/mol$

The amount of heat absorbed by a mole of sample in meting has been the molar heat of fusion.

Thus, the molar heat of fusion of X has been 775.6 cal/mol. Thus, option C is correct.

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