Calculate the number of moles in this quantity: 250 ml ethyl alcohol,C2H5OH(=0.789 g/ml)
To calculate the number of moles in a given quantity of a substance, you need to use the formula:
moles = mass / molar mass
First, we need to determine the mass of ethyl alcohol in 250 ml.
Given that the density of ethyl alcohol is 0.789 g/ml, we can calculate the mass as follows:
mass = volume * density
mass = 250 ml * 0.789 g/ml
mass = 197.25 g
The molar mass of ethyl alcohol (C2H5OH) can be calculated by adding the atomic masses of each element in its molecular formula:
Molar mass(C2H5OH) = 2 * molar mass(C) + 6 * molar mass(H) + molar mass(O)
The molar masses of carbon (C), hydrogen (H), and oxygen (O) are approximately 12 g/mol, 1 g/mol, and 16 g/mol, respectively.
Molar mass(C2H5OH) = 2 * 12 g/mol + 5 * 1 g/mol + 16 g/mol
Molar mass(C2H5OH) = 46 g/mol
Now we can calculate the number of moles using the formula:
moles = mass / molar mass
moles = 197.25 g / 46 g/mol
Calculating this gives us:
moles ≈ 4.28 mol
Therefore, there are approximately 4.28 moles of ethyl alcohol in 250 ml.
To calculate the number of moles in a given quantity of a substance, we need to use the concept of molar mass and the formula:
Number of moles = Mass of the substance / Molar mass of the substance
In this case, we have 250 ml of ethyl alcohol (C2H5OH) with a density of 0.789 g/ml.
Step 1: Calculate the mass of ethyl alcohol using the given density.
Mass = Density × Volume
Mass = 0.789 g/ml × 250 ml
Mass = 197.25 g
Step 2: Calculate the molar mass of ethyl alcohol (C2H5OH).
To calculate the molar mass of ethyl alcohol (C2H5OH), we need to sum up the atomic masses of all the atoms in the formula.
Molar mass of C2H5OH = (2 × Atomic mass of C) + (6 × Atomic mass of H) + (1 × Atomic mass of O)
From the periodic table, the atomic mass of C is approximately 12.01 g/mol, the atomic mass of H is approximately 1.01 g/mol, and the atomic mass of O is approximately 16.00 g/mol.
Molar mass of C2H5OH = (2 × 12.01) + (6 × 1.01) + (1 × 16.00)
Molar mass of C2H5OH ≈ 46.07 g/mol
Step 3: Calculate the number of moles.
Number of moles = Mass of the substance / Molar mass of the substance
Number of moles = 197.25 g / 46.07 g/mol
Number of moles ≈ 4.28 moles
Therefore, there are approximately 4.28 moles of ethyl alcohol in 250 ml.
convert the 250ml to mass by using density.
then, moles=mass/molmass