A solution containing 16.9 grams of a molecular compound dissolved in 250 grams of water has a freezing point of -0.744 degrees celcius.
Find the molaltity of the solution.
I have -0.744=-1.86*m*i. how do i find i.
what is the gfm of the solute?
I know that the GFM=Mass/moles. So i have 16.9/moles. how do i do that?
Determine the boiling point. how do i do that??
To find the value of "i" in the equation -0.744 = -1.86 * m * i (where m represents the molality of the solution), you need to know the number of particles produced by the solute in the solution. This value is known as the van't Hoff factor (i) and depends on the nature of the solute. For a molecular compound, i may vary based on the dissociation of the compound. You will need to look up the specific compound in a reliable reference source or consult the literature to determine the van't Hoff factor for that compound.
To calculate the formula mass or formula weight (GFM) of the solute, you're correct in using the equation GFM = mass / moles. In this case, you have the mass (16.9 grams), but you need to find the number of moles. You can use the equation moles = mass / molar mass. The molar mass of the compound can be found by summing up the atomic masses of its constituent elements. You can find the atomic masses in the periodic table. Once you have the molar mass, you can divide the mass (16.9 grams) by the molar mass to find the number of moles of the solute.
To determine the boiling point of the solution, you need to know the boiling point elevation constant (Kb) for the solvent (water, in this case). Kb is a characteristic property of a solvent and can also be found in reference sources or literature. Once you have the value of Kb for water, you can use the equation ΔTb = Kb * m * i, where ΔTb (change in boiling point) can be calculated by subtracting the boiling point of the pure solvent (water) from the observed boiling point of the solution. Rearranging the equation, you can solve for the molality (m). Note that you will need to convert temperatures to Kelvin (K) by adding 273 to the Celsius (°C) values in these calculations.
In summary:
- Find the van't Hoff factor (i) by referring to reliable sources.
- Calculate the molar mass of the solute using the atomic masses of its constituent elements.
- Determine the molality (m) using the observed freezing point depression equation, -0.744 = -1.86 * m * i.
- Calculate the boiling point elevation (ΔTb) using the equation ΔTb = Kb * m * i, with Kb being the boiling point elevation constant for water.
- Convert temperatures to Kelvin to perform these calculations, if necessary.
i is the number of particles. Since the problem states that this a molecular compound, then i = 1. That allows you to calculate molality from delta T = kf*m.
Then molality = # mols/kg solvent
molality = # mols/0.250 kg water an this allows you to calculate # mols.
Finally, # mols = g/GFM. You know # mol and g, calculate GFM.
Determine boiling point.
delta T = kb*m
You know molality, you know Kb (or can look it up--I think it's about 0.5 degrees C/m). Then boiling point water is 100 + delta T.
Post your work if you get stuck. Please note the correct spelling of Celsius.