If your unknown solid has an impurity that is insoluble in cyclohexane the molar mass of the unknown solid being recorded as high.
Impurities are chemical substances inside a certain amount of liquid, gas, or solid, but are different from the chemical composition of the material itself.
Also, there will be an increase in molecular weight obtained because the mass of the solute would now include the actual mass of solute that is changing and the excess mass of the impurity from the unknown solid this will increase the molar mass.
Therefore, If your unknown solid has an impurity that is insoluble in cyclohexane the molar mass of the unknown solid is recorded as high.
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