During its combustion, ethane combines with oxygen to give carbon dioxide and water. A sample of ethane was burned completely and the water that formed has a mass of 1.61 grams. How many grams of ethane were in the sample?
2C2H6 + 7O2 ==> 4CO2 + 6H2O
mols H2o formed = grams/molar mass = ?
Using the coefficients in the balanced equation, convert mols H2O to mols ethane.
Now convert mols ethane to grams; grams = mols ethane x molar mass ethane.
To determine the mass of ethane in the sample, we need to use the stoichiometry of the combustion reaction.
The balanced chemical equation for the combustion of ethane is:
C2H6 + O2 -> CO2 + H2O
From the equation, we can see that for every 2 moles of ethane (C2H6) burned, 2 moles of water (H2O) are produced.
1 mole of water (H2O) has a molar mass of approximately 18 grams.
We can use this information to calculate the number of moles of water produced in the combustion reaction:
Number of moles of water = mass of water / molar mass of water
= 1.61 grams / 18 grams/mol
≈ 0.0895 moles of water
Since the stoichiometry ratio between ethane and water is 2:2, we can conclude that the number of moles of ethane burned is equal to the number of moles of water produced.
Thus, the number of moles of ethane = 0.0895 moles.
The molar mass of ethane (C2H6) is approximately 30 grams/mol.
Therefore, the mass of ethane in the sample can be calculated as:
Mass of ethane = number of moles of ethane x molar mass of ethane
= 0.0895 moles x 30 grams/mol
= 2.685 grams
Therefore, there were approximately 2.685 grams of ethane in the sample.
To determine the mass of ethane in the sample, we can use the balanced chemical equation for the combustion of ethane.
The balanced equation is:
C2H6 + 7/2 O2 -> 2 CO2 + 3 H2O
Based on this equation, we can see that for every 3 moles of water produced, we have 1 mole of ethane. So, we need to find the number of moles of water formed, and then convert it to moles of ethane, and finally calculate the mass of ethane.
Step 1: Convert mass of water to moles of water.
To do this, we need to know the molar mass of water (H2O). The molar mass of hydrogen (H) is approximately 1 g/mol, and the molar mass of oxygen (O) is approximately 16 g/mol. Therefore, the molar mass of water is 2 * 1 g/mol (for hydrogen) + 16 g/mol (for oxygen) = 18 g/mol.
To find the number of moles of water, we divide the mass of water by its molar mass:
moles of water = mass of water / molar mass of water
moles of water = 1.61 g / 18 g/mol
moles of water ≈ 0.0894 mol
Step 2: Convert moles of water to moles of ethane.
From the balanced equation, we know that for every 3 moles of water formed, 1 mole of ethane is consumed.
moles of ethane = (moles of water) / 3
moles of ethane ≈ 0.0894 mol / 3
moles of ethane ≈ 0.0298 mol
Step 3: Convert moles of ethane to mass of ethane.
To do this, we need to know the molar mass of ethane (C2H6). The molar mass of carbon (C) is approximately 12 g/mol, and the molar mass of hydrogen (H) is approximately 1 g/mol. Therefore, the molar mass of ethane is 2 * 12 g/mol (for carbon) + 6 * 1 g/mol (for hydrogen) = 30 g/mol.
mass of ethane = moles of ethane x molar mass of ethane
mass of ethane ≈ 0.0298 mol x 30 g/mol
mass of ethane ≈ 0.894 g
Therefore, the mass of ethane in the sample is approximately 0.894 grams.