A certain alcoholic beverage contains only ethanol (C2H6O) and water. When a sam

Question

A certain alcoholic beverage contains only ethanol (C2H6O) and water. When a sample of this beverage undergoes combustion, the ethanol burns but the water simply evaporates and is collected along with the water produced by combustion. The combustion reaction is
C2H6O(l)+3O2(g)2CO2(g)+3H2O(g)
When a 10.35 g sample of this beverage is burned, 11.07 g of water is collected.

What is the mass in grams of ethanol in the original sample?

Express your answer using two decimal places.

What is the mass of water in the original sample?

Express your answer using two decimal places.

Explanation / Answer

composition of beverage sample: ethanol and water

ethanol is burnt according to following reaction:

C2H6O(l) + 3 O2(g)2 CO2(g)+3 H2O (g)

1 mole of ethanol gives 3 moles of H2O

46 g of ethanol = 3*18 g of H2O

46 g of ethanol = 54 g of H2O

Now, the problem given is:

10.35 g sample of beverage is burned, 11.07 g of water is collected

we have to find the mass in grams of ethanol in the original sample.

Step 1: calculate the mass of water formed by ethanol and water in a sample

Ist case: sample contains pure ethanol.

Since; calculated above 46 g of ethanol = 54 g of H2O

10.35 g ethanol will produce = 12.15 g H2O

2nd case : sample contains pure water.

Then 10.35 g H2O will produce 10.35 g H2O

Now, calculate the difference between two to find the amount of water produced by ethanol = 12.15-10.35 = 1.8 g  H2O

Sice; total mass of water collected (water formed from combustion + water present in beverage) = 11.07 g

So , the actual amount of water produced by ethanol = total mass of water collected - amount of water produced by water in sample = 11.07 g - 10.35 g = 0.72 g H2O

Step 2 :

Calculate the ratio of the water produced by ethanol in mixture to determine % of mixture :

0.72
.8 = 72
80 = 0.4 = 40%

40% is ethanol

and 60% remaining is water

Step 3 : to calculate the mass of etahnol and water in 10.35 g sample

40% is ethanol

thus 40% of 10.35 = 4.14 g of ethanol

60% remaining is water

60% of 10.35g sample = 6.21 g water

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