0.015 moles of a compound are dissolved in 18 fl. oz. of water. At what temperature will the solution begin to freeze? The density of water is 1.00g/mL
what will be mass of 0.015 moles of sodium hydroxide sulphet where the molar mass of sodium hydroxide 120g/moles.
To determine the temperature at which the solution will begin to freeze, we need to use the concept of freezing point depression. This is based on the fact that adding a solute to a solvent lowers the freezing point of the solvent.
To calculate the freezing point depression, we need to know the molal concentration (m) of the solution. Molal concentration is defined as the number of moles of solute per kilogram of solvent.
To find the molal concentration (m), we can use the formula:
m = (moles of solute) / (mass of solvent in kg)
First, let's convert the volume of water from fluid ounces to milliliters (ml), since the density of water is given in grams per milliliter (g/mL).
1 fl. oz. is approximately equal to 29.57 ml (1 fl. oz. ≈ 29.57 ml)
So, 18 fl. oz. is equal to 18 × 29.57 ml = 532.26 ml
Next, we need to calculate the mass of the water in grams, using its density:
mass of water = volume of water × density of water
mass of water = 532.26 ml × 1.00 g/mL = 532.26 g
Now, we can calculate the molal concentration (m):
m = (0.015 moles) / (532.26 g / 1000)
m = 0.015 moles / 0.53226 kg
m ≈ 0.0282 mol/kg
The freezing point depression (ΔTf) can be calculated using the formula:
ΔTf = Kf * m
where Kf is the molal freezing point depression constant for water. For water, Kf is approximately 1.86 °C/molal.
ΔTf = 1.86 °C/molal * 0.0282 mol/kg
ΔTf ≈ 0.0525 °C
Finally, we can determine the temperature at which the solution will begin to freeze by subtracting the freezing point depression from the freezing point of pure water, which is 0 °C.
Temperature of freezing = 0 °C - 0.0525 °C ≈ -0.0525 °C
Therefore, the solution will begin to freeze at approximately -0.0525 °C.
Convert 18 fl oz to grams and to kg. 1 oz = 28.35 grams.
molality = mols/kg solvent
Solve for molality.
Then delta T = Kf*m
You know Kf and m, solve for delta T, then subtract from zero C to find the new freezing point.