What is the solution's freezing point: 15 g of CH4N2O (Molar mass = 60.055 g/mol) in 200. g of H2O? (Kf = 1.86 (°C·kg)/mol)
1 answer:
Ok to answer this question we firsst need to fin the number of mol of Urea (CH4N2O). to do this we simply :
1 mol of urea =15/60.055 = 0.25mol
therefore 200g of water contain 0.25mol
the next step is to determine the malality of our solution in 200g of water, to do this we say:
200 g = 1Kg/1000g = 0.2kg
therefor 0.25mol/0.2Kg = 1.25mol/kg
and from the equation:
we know that i = 1
we are given Kf
b is the molality that we just calculated
therefore;
the solutions freezing point is -2.325°C
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Explanation:
Polarity is defined as the development of partial charges on the atoms of a molecule. In a water molecule, there are hydrogen and oxygen atoms.
Due to the difference in electronegativity of both hydrogen and oxygen atom there is development of partial positive charge on hydrogen atom and a partial negative charge on oxygen atom.
So, when bond between hydrogen and oxygen will break down then it will form hydrogen ions () and oxygen ions (
).
Ion-dipole interactions are defined as the interactions that occur when an ion interacts with the dipole of a molecule.
When an electron is added to a neutral atom to convert it into a negative ion then the amount of change taking place in its energy is known as electron affinity.
So, oxygen atom has an affinity towards cations and hydrogen atom has an affinity for anions.
Thus, we can conclude that following interactions and processes contribute to the dissolution of ionic compounds in water:
1. Affinity of oxygen towards cations
2. Ion–dipole interactions
4. Hydration
6. Affinity of hydrogen towards anions