Multiple choice

A mixture of ethanol and $CCl_{4}$ has $30\%$ $CCl_{4}$ by weight, what is mole fraction of $CCl_{4}$ in the mixture?

  1. $0.11$
  2. $0.89$
  3. $0.25$
  4. $0.67$
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A Correct answer
Explanation

Assuming the mixture is ethanol (C2H5OH, molar mass 46) and CCl4 (molar mass 154), 30g of CCl4 and 70g of ethanol give moles: n(CCl4) = 30/154 = 0.195 and n(ethanol) = 70/46 = 1.52. Mole fraction = 0.195 / (0.195 + 1.52) = 0.113.

AI explanation

In a 100 g sample, there are 30 g of CCl4 and 70 g of ethanol. The moles of CCl4 are its mass divided by its molar mass (154 g/mol), which is 30 divided by 154, or approximately 0.195 moles. The moles of ethanol are its mass divided by its molar mass (46 g/mol), which is 70 divided by 46, or approximately 1.522 moles. The mole fraction of CCl4 is its moles divided by the total moles, 0.195 divided by 1.717, which equals approximately 0.11.

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