What mass of glucose must be fermented to give 5.0kg of ethanol?

ScottyBoy94

C6H1206(aq) ----> 2C2H5OH(aq) + 2CO2(g)

Help :frown:

Reply 1

Rubgish

1) Work out the relative atomic masses of each of those three substances
2) find the ration of ethanol produced compared to glucose
3) Use ratio to find the quantity of glucose.

Reply 2

ScottyBoy94

Rubgish

1) Work out the relative atomic masses of each of those three substances
2) find the ration of ethanol produced compared to glucose
3) Use ratio to find the quantity of glucose.

Okay ive done the 1st part, how do i find the 2nd part out

Reply 3

Rubgish

ScottyBoy94

Okay ive done the 1st part, how do i find the 2nd part out

For the relative atomic mass of 1 glucose, you produce the relative atomic mass of 2 ethanol. Hence (made up numbers) if glucose was 200 and ethanol was 80, then 200 glucose would produce 160 ethanol. Hence the ratio is 200:160 or 5:4.

This means if you want 5kg of ethanol, then you need to divide it by 4 and multiply it by 5 to find the mass of glucose needed, so in this example it would be 6.25kg of glucose to than 5kg of ethanol.

Do it with the real numbers and you should get the answer :smile:

Reply 4

thegodofgod

ScottyBoy94

Okay ive done the 1st part, how do i find the 2nd part out

So how many moles of C2H5OH in 5.0 kg?

Moles = Mass / Mr
= 5000 / 46

you know that the ratio of Glucose : Ethanol is 1 : 2 (imagine there's a 1 placed in front of C6H12O6 in the equation).

therefore, there are (5000/46) / 2, which is 5000/92.

So moles of Glucose = 5000/92.

Mass = Moles x Mr
= (5000/92) x 180

this will give the answer in grams, so convert it into kg by dividing the answer by 1000.