Question #cffa0

2 Answers
Feb 2, 2015

When you are dealing with gases, it is necessary to have values for pressure and temperature. SInce no values are provided, I'll assume you are at STP - 1 atm and 273.15 K.

What basically takes place is the combustion of sucrose, or table sugar.

C12H22O11+12O211H2O+12CO2

The first thing you must look for is mole ratios, that will give you an idea on how to proceed once you determine how many moles of sucrose you have.

Notice that every 1 mole of sucrose needs 12 moles of oxygen for the reaction to take place - you have a 1:12 mole ratio between sucrose and oxygen. This tells you that whatever number of moles of sucrose you have, you'll need 12 times more moles of oxygen.

Determine the moles of sucrose you have by using its molar mass - 342.3 g/mol

2.48 g1 mole342.3 g=0.00725 moles sucrose

We've established that you need 12 times more moles of oxygen, so

0.00725 moles sucrose12 moles oxygen1 mole sucrose=0.0870 moles

Now that you know how mnay moles of oxygen you have, you can use the fact that 1 mole of any ideal gas occupies exactly 22.4 L at STP - this is known as the molar volume of a gas.

If 1 mole occupies 22.4 L, and you only have 0.0870 moles, the volume of oxygen you'll need will be obviously smaller than 22.4 L

0.0870 moles22.4 L1 mole=1.95 L oxygen at STP.

If you're not at STP, use the ideal gas law equation to solve for V:

PV=nRTV=nRTP - then just plug in whatever values you have for pressure and temperature.

Feb 2, 2015

2.09 litres of O2 are required.

The Mr of the carbohydrate from which the "gummy bear" is composed =[(12×12)+(22×1)+(11×16)]=342

I will assume we are at NTP where the volume of 1 mole of gas = 24 litres.

From the equation we can see that:

1 mole of gummy bear needs 12 moles O2

1 mole needs 12×24=288 litres O2

So 342g needs 288 litres O2

So 1g needs 288342 litres O2

So 2.68g needs 288342×2.48=2.09 litres