Ethanol's Formula: What Is It?
Ethanol or ethyl alcohol is known simply as alcohol. In its most basic state, the general ethanol properties are: colorless, miscible with water, and flammable.
Basically, ethanol is produced when the sugar content derived from agricultural crops is fermented. This is then followed by distillation, and the result is 95% ethanol, which is the highest concentration that can be achieved by this process.
To make 100% ethanol, molecular sleves should be used. When produced from biomass, however, it is called bioethanol. In the US, corn is the main crop used in the production of ethanol. One bushel of corn can produce around 2.8 gallons or ethanol at a rate of 0.42 liter per kilogram. However, aside from using molecular sleves and biomass material, ethanol can also be produced by hydrating ethylene gas.
The ethanol formula is characterized by the following:
Ethanol’s Structural Formula
Ethanol is a straight chain primary alcohol or Alkanol with two carbon atoms, six hydrogen atoms, and one oxygen atom. The two carbon atoms are the central point of the structure and form a C-C bond to each other through a process known as Cate-nation. The first carbon atom is combined with the three hydrogen atoms to form a methyl group. The second carbon atom, on the other hand, is combined with two other hydrogen atoms plus the hydroxyl functional group.
The chemical formula of ethanol is CH3CH2OH.
The molecular formula, on the other hand, is C2H5OH; this is the most commonly used formula that represents ethanol. When broken down, however, ethanol’s chemical structure is basically an ethyl group attached to a hydroxyl functional group.
In sum, ethanol’s chemical equation is CH3CH2 + OH = CH3CH2OH.
The shortest formula for ethanol, or its abbreviation, is EtOH, with “Et” representing its Alkyl Ethyl group and OH as the functional group.
When ethanol is being fermented, the chemical structure of glucose changes. Glucose, whose original chemical formula is C6H12O6, converts one mole into two moles or ethanol and two moles of carbon dioxide. This is how the process of fermentation converts glucose into ethanol.
Prior to fermentation, however, one glucose mole is broken down by two pyruvate moles in a process called glycolysis.
Ethanol’s Molar Mass
The empirical formula of ethanol is C2H6O. It is quite unique and is a bit complex in comparison to other organic compounds. It is derived using the simplest ratios of the elements that ethanol is made up of. Ethanol contains the following elements at these ratios:
• 52.17% carbon (C) = 4.35
• 34.78% oxygen (O) = 2.17
• 13.05% hydrogen (H) = 13.04
The ratios are calculated by dividing the percentage composition of each element by their respective molecular masses.
Based on the molar mass of carbon (12 g/mol), the molar mass of oxygen (16 g/mol), and the molar mass of hydrogen (1 g/mol), ethanol has a resulting molar mass of 46.068 g/mol. However, the correct answer to the question, “what is the molecular weight of ethanol or the “mw” of ethanol?” is 46.0 amu. However, its exact mass is 46.0416864814 g/mol.
Surface Tension of Ethanol
Surface tension, also known as SFT or surface tension values, is measured in dynes/cm, which refers to the force in dynes required to break through a film with a 1-centimeter length. It is also stated in ergs per square centimeter.
The surface tension of ethanol is only 22.39 dyn/cm at 25 degrees Celsius. This means that it would only take a force of 22.3 dynes to break a surface film of water that is 1 cm long. It is quite low compared to the surface tension of water, which is 72.8, and the surface tension of mercury, which is 465.
However, when you add a few percent of ethanol to water, it can cause a sharp reduction in the surface tension of water due to the significantly lower ethanol surface tension.
pH of Ethanol
The pH of ethanol is derived by the ethanol pKa value. The formula to calculate the pH is pH = pKa – log [AH/A] where [AH/A] is the ratio of disassociated species to the undisassociated species in the solution.
pKa of Ethanol
The ethanol pKa or acidity is 15.9. pKa is the symbol for the acid dissociation constant at the logarithmic scale. An acid dissociation constant, known simply as acidity constant or acid ionization constant, is the measurement of the strength of an acid in a solution. It is known as the equilibrium constant for the dissociation in acid-base reactions.
The formula for pKa is pKa = -logKa. Substances with higher pKa values have smaller dissociation extents, while lower pKa values indicate weak acids. Weak acids usually have a pKa value of approximately -2 to 12 in range. Outside of this range, the acid is considered to be a strong acid. Since the pKa of ethanol is 15.9, it means it is a relatively strong acid. On the other hand, ethanol’s basicity or pKb is -1.9.
Vapor Pressure of Ethanol
Vapor pressure, also called the equilibrium vapor pressure, is the equilibrium pressure of a vapor above its condensed liquid state. The vapor pressure of ethanol is 1187 torr, while that of water is just 525 torr. This is equivalent to 78.47 mmHg when measured at 30.0 degrees Celsius or to 5.95 kPa at 20 degrees Celsius.
Take note that the vapor pressure of ethanol changes as the temperature also changes. Generally, however, ethanol has a heat of vaporization of 38.56 kj/mol. To measure pressure at any temperature, you will need to use a manometer.
Viscosity of Ethanol
The viscosity of a fluid is the measure of its resistance to bring deformed by stress. The viscosity of ethanol can be measured in two ways: the viscosity of ethanol as a liquid and its viscosity as vapor. Ethanol’s liquid viscosity is 0.00037 kg/ms or 0.0012 Pa s at 20 degrees Celsius, while its vapor viscosity is 108 x 10-7 kg/ms.
Thermodynamic Properties of Ethanol
As for the thermodynamic properties of ethanol, its critical point is at 514 K or 241 degrees Celsius with a 63 bar pressure level, while its triple point is 150 K (-123 degrees Celsius) at 0.00043 Pa.
Ethanol has an Std enthalpy change of fusion of +4.9 kJ/mol, and an Std entropy change of fusion of +31 J/(molK). It also has an Std enthalpy change of vaporization of +38.56 kJ/mol and an Std entropy change of vaporization of 109.67 J/(molK). Ethanol’s molal freezing point is -1.99 degrees Celsius kg/mol and its molal boiling point is 1.19 degrees Celsius kg/mol.
Its solid properties are determined by a -277.7 jK/mol Std enthalpy change of formation, a standard molar entropy of 160.7 J/(mol k), and a heat capacity of 111.46 J/(mol K).
In its liquid form, its Std enthalpy change of formation is -277.38 kJ/mol, while its standard molar entropy is 159.9 J/(mol K). It has a -1370.7 kJ/mol enthalpy of combustion and a heat capacity of 112.4 J/(mol K).
In its gas form, it has an Std enthalpy change of formation of -235.3 jK/mol, a standard molar entropy of 283 J/(mol K), and a heat capacity of 78.28 J/(mol K) at 90 degrees Celsius and 87.53 J/(mol K) at temperatures ranging between 110 and 220 degrees Celsius. Its heat capacity ratio in gas form, on the other hand, is 1.13 at 90 degrees Celsius.
Ethanol Formula Facts
Ethanol also has a liquid density of 0.789 g/mL and a vapor density of 0.0015 g/mL. However, the density of ethanol changes as temperature also changes.
During vaporization, however, ethanol can produce heat levels of up to 855 J/g. Its boiling point is 78 degrees Celsius (172 degrees Fahrenheit or 351 K), while its melting point is -114 degrees Celsius (-173 degrees Fahrenheit or 159 K). Ethanol also has a refractive index of 1.36, and a dipole moment of 1.69 D.
Due to the basic ethanol properties, when used as a drug, ethanol can be administered through intramuscular, intravenous, oral, and topical means. It is then metabolized in the liver. When used as a fuel, however, it has an auto-ignition temperature of 362 degrees Celsius.
Ethanol fuel has an energy content of 21.2 MJ/L or 26.8 MJ/kg. E85 ethanol blend, however, has a higher energy content of 25.2 MJ/L or 33.2 MJ/kg. Gasohol, which is a 90% gasoline and 10% ethanol mixture produced in the US has the highest energy content of the three at 33.7 MJ/L or 47.1 MJ/kg; this is because it has more parts gasoline than ethanol.