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To solve boiling point elevation problems, you need to know the following things:
-- the identity of the solute (the thing you are adding to the liquid)
-- the identity of the solvent (the liquid)
-- whether the solute is molecular or ionic, and if ionic, how many ions it forms
-- the amount of solute (in grams or moles)
-- the amount of solvent (in kilograms)
-- the value of Kf of the solvent (for water, it is 0.52 K·kg/mol (or 0.52 °C molal-1)
Then you use the following equation:
∆T = i * Kf * m
where ∆T is the change in the freezing point, "i" is the number of molecules or ions formed upon addition to the solvent, Kf is the freezing point depression constant, and "m" is the molality of the solution.
The Kf of water for a boiling point elevation is known and is equal to 0.52 °C·kg/mol (or 0.52 °C molal-1). Notice it is positive -- for freezing point depression problems, the value of Kf is negative.
The value of "i" has to do with what you add to the water. If you added sugar, a molecular compound the value of "i" is 1.0. If you add a ionic compound like NaCl, the value of "i" is 2.0 because for every 1 molecule of NaCl, you make 2 ions: one Na+ and one Cl- in water. For MgCl2, the value of "i" is thus 3.0 (for each MgCl2 you get one Mg2+ and two Cl- ions, so a total of 3 ions).
To find "m," the molality of a solution you need to know the number of moles of solute and the number of kilograms of solvent (m = moles/kg). If you are given the number of grams of solute, the number of moles is found from the mass and the molar mass of the solute.
grams of solute ÷ molar mass of solute = moles of solute
To find the molality, just divide the moles of solute by the kilograms of solvent moles of solute ÷ kilograms solvent = molality Note: If you are given the volume of the solvent instead of the mass, use the density of the solvent to convert -- the density of water is 1 kilogram per liter)
Liters of solvent * density of solvent = kilograms of solvent
Now just plug all the numbers into the equation at the top of the answer!
See the Web Links and Related Questions for more information!
What else can I help you with?
What quantity represents the ration of the number of moles of solute per kilogram of solvent?
Mol is a cocentration unit !
When a certain amount of calcium chloride (CaCl2) was dissolved 100.g of water the boiling point rose from 100.0C to 104.4C calculate the molality of this solution.?
Delta T = imKI = van't Hoff factor = 3 for CaCl2 m = molality = moles solute/kg solvent = ? K = boiling point constant for water = 0.512 Delta T = change in temperature = 4.4 deg C Plug in the values and solve for m
Formula for molality?
Molality (m) is calculated by dividing the number of moles of solute by the mass of the solvent in kilograms and is expressed in mol/kg. The formula for molality is: [ molality (m) = \frac{moles\ of\ solute}{mass\ of\ solvent\ in\ kg} ]
What is the molality of a substance made by dissolving 2 moles of NaOH in 10 kg of water?
Molality is moles solute per kilograms of solvent, so 2/10=0.2m.
What are the molality and mole fraction of solute in a 25.5 percent by mass aqueous solution of formic acid (HCOOH)?
The molality is 5,54.
How can one determine the molality of a solution using the freezing point depression method?
To determine the molality of a solution using the freezing point depression method, you need to measure the freezing point of the pure solvent and the freezing point of the solution. By comparing the two freezing points, you can calculate the change in temperature. Using the formula T Kf m, where T is the change in temperature, Kf is the cryoscopic constant of the solvent, and m is the molality of the solution, you can solve for the molality of the solution.
How do you calculate the molality of a solution?
To calculate the molality of a solution, you divide the moles of solute by the mass of the solvent in kilograms. The formula for molality is: Molality (m) moles of solute / mass of solvent (in kg).
How can one determine the molar mass from molality?
To determine the molar mass from molality, you can use the formula: Molar mass (molality x molar mass of solvent) / molality of solute. This equation helps you calculate the molar mass of a substance based on its molality in a solution.
What quantity represents the ration of the number of moles of solute per kilogram of solvent?
Mol is a cocentration unit !
What is the formula for calculating the molality (m) of a solution?
The formula for calculating the molality (m) of a solution is: molality (m) moles of solute / kilograms of solvent.
What is the relationship between molality and molar mass in a solution?
The relationship between molality and molar mass in a solution is that molality is directly proportional to molar mass. This means that as the molar mass of a solute increases, the molality of the solution also increases.
What is the molality of a substance?
Molality is the number of moles of a solute divided by the weight of the solvent in kilograms.
What is the relationship between the molar mass and molality of a solution?
The relationship between the molar mass and molality of a solution is that the molality of a solution is dependent on the molar mass of the solute. Molality is calculated by dividing the number of moles of solute by the mass of the solvent in kilograms. Therefore, the molar mass of the solute directly affects the molality of the solution.
What is molality?
Concentration
How are concentrations in solutions quantified?
through molarity,molality, normality. through molarity,molality, normality.
Why you use molality in biology experiments?
Molality is used when temperature varies in an exothermic or endothermic reaction because it is not dependent on temperature or pressure. Molality does not depend on tempratute whereas molarity does.
How can the molality of a solution be converted to its corresponding mole fraction?
To convert the molality of a solution to its corresponding mole fraction, you can use the formula: Mole fraction (molality / (molality 1000)) This formula calculates the ratio of the moles of solute to the total moles of solute and solvent in the solution.
