A mixture of ethyl alcohol (molecular mass = 46.1 u) and water (molecular mass = 18.0 u) contains one mole of molecules. The mixture contains 20.0 g of ethyl alcohol. What mass m of water does it contain?

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Chemistry

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30 July, 15:40

A mixture of ethyl alcohol (molecular mass = 46.1 u) and water (molecular mass = 18.0 u) contains one mole of molecules. The mixture contains 20.0 g of ethyl alcohol. What mass m of water does it contain?

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Ryan Harrison · Answer 1

10.2 g

Explanation:

A mixture of ethyl alcohol (molecular mass = 46.1 u) and water (molecular mass = 18.0 u) contains one mole of molecules.

The mixture contains 20.0 g of ethyl alcohol. The molar mass of ethyl alcohol is 46.1 g/mol. The moles of ethyl alcohol are:

20.0 g * (1 mol / 46.1 g) = 0.434 mol

The sum of the moles of ethyl alcohol and the moles of water is 1 mole.

n (ethyl alcohol) + n (water) = 1 mol

n (water) = 1 mol - n (ethyl alcohol) = 1 mol - 0.434 mol = 0.566 mol

The molar mass of water is 18.0 g/mol. The mass of water is:

0.566 mol * (18.0 g/mol) = 10.2 g