## Two Component Systems

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## 1

The term Mole Fraction of substance A in a mixture of A and B means

(select ALL the correct definitions)

The fraction of the molecules present which are A
The number of moles of A divided by the number of moles of A plus the number of moles of B
The number of moles of A divided by the number of moles of B
The fraction of the amounts in moles of the two substances which is A
The number of moles of A in a gramme of mixture
The number of moles of A in a litre of mixture

## 2

Some posh Scotch whiskys contain 43% by volume alcohol. Such a solution in fact contains 36g alcohol per 100g of solution. Given that Mr for alcohol is 46.1 g.mol-1, calculate the mole fraction of alcohol in such a mixture. Assume the mixture contains only alcohol and water.

Give your answer to TWO decimal places

## 3

Calculate xA in wine if a sample of 200g contains 17 g alcohol (10.5%v/v)

(again C2H5OH = 46.1)

Give your answer to TWO significant figures - remember that preceding zeros do not count towards the number of significant figures.

## 4

Motor antifreeze is mainly a solution of ethylene glycol (1,2-dihydroxyethane, Mr 62.07) in water.
Calculate the mole fraction of a 25 % solution, by weight, i.e.100g solution contains 25 g glycol.

## 5

Golden syrup is 85% sugars and 15% water approximately. Assuming the sugars are sucrose (C12H22O11, Mr 342.3), calculate the mole fraction of sucrose.

Give your answer to TWO decimal places

## 6

Calculate the mole fraction of water in the golden syrup

Give your answer to TWO decimal places

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