Here is a worked example of a stoichiometry problem. Just follow the steps. Post your work if you get stuck.
http://www.jiskha.com/science/chemistry/stoichiometry.html
http://www.jiskha.com/science/chemistry/stoichiometry.html
= 6.5 mL ethanol
10grams of sucrose รท 180.15768g/mol sucrose ร 2mol ethanol ร 46.06904g/mol ethanol รท 0.79g/mL
= 6.5 mL ethanol
Step 1: Find the molar mass of sucrose.
Sucrose, also known as table sugar, has the chemical formula C12H22O11. You can find the atomic masses from the periodic table.
C: 12.01 g/mol
H: 1.01 g/mol
O: 16.00 g/mol
Now, calculate the molar mass of sucrose by adding up the atomic masses:
(12.01 * 12) + (1.01 * 22) + (16.00 * 11) = 342.34 g/mol
So, the molar mass of sucrose is 342.34 g/mol.
Step 2: Convert grams of sucrose to moles.
Use the formula: Moles = mass / molar mass
Moles of sucrose = 10 g / 342.34 g/mol โ 0.0292 mol of sucrose
Step 3: Determine the stoichiometry between sucrose and ethanol.
The balanced equation for fermentation of sucrose is:
C12H22O11 + H2O โ 4C2H5OH + 4CO2
From the equation, you can see that 1 mole of sucrose produces 4 moles of ethanol.
Step 4: Calculate the theoretical amount of ethanol.
Multiply the moles of sucrose by the stoichiometric ratio:
0.0292 mol of sucrose x (4 mol of ethanol / 1 mol of sucrose) = 0.1168 mol of ethanol
Step 5: Convert moles of ethanol to grams.
Since you have the density of ethanol, you can convert moles to grams using the formula:
Grams = moles x molar mass
The molar mass of ethanol (C2H5OH) is:
(12.01 * 2) + (1.01 * 6) + (16.00 + 1) = 46.07 g/mol
Grams of ethanol = 0.1168 mol x 46.07 g/mol โ 5.38 g of ethanol
So, the theoretical amount of alcohol to be produced from 10 grams of sucrose is approximately 5.38 grams.