1) The molecular mass of a substance was determined by the freezing point depression technique. The minimum data required for the determination are:
a) delta T and Kf only
b) delta T, Kf, and mass of solute
c) delta T, Kf, mass of solute, and mass of solvent
d) delta T, Kf, mass of solute, mass of solvent, and identity of solvent
e) delta T, Kf, mass of solute, mass of solvent and identity of mass and solvent.
I chose delta T, Kf, and mass of solute.
2)Ethanol and water are both liquids at or near room temperature. When a sample of ethanol is poured into a beaker containing water, the two liquids
a) are miscible because each can hydrogen bond with the other.
b) are immiscible because each has strong hydrogen bonds that cannot be broken.
c) are miscible because both are liquids and all liquids are miscible.
d) are immiscible because organic and non-organic compounds cannot mix.
I chose that they are miscible because each can hydrogen bond with each other.
Are these correct?
Responded to a later post.
1) Your choice for the first question is correct. The minimum data required for determining the molecular mass of a substance using the freezing point depression technique are delta T (change in freezing point), Kf (cryoscopic constant specific to the solvent), and the mass of the solute.
To determine the molecular mass using freezing point depression, you need to measure the change in freezing point (delta T) of the solvent when a known mass of solute is added. The cryoscopic constant (Kf) is a characteristic property of the solvent and is used to convert the change in freezing point to molality (moles of solute per kilogram of solvent). With the delta T, Kf, and mass of solute, you can apply the formula for freezing point depression to calculate the molecular mass of the solute.
2) Your choice for the second question is incorrect. Ethanol and water are indeed miscible because they can both form hydrogen bonds with each other.
Miscibility refers to the ability of two or more substances to mix and form a homogeneous mixture. In the case of ethanol and water, both molecules are polar and can participate in hydrogen bonding. Ethanol has an -OH group, and water also has -OH groups. These hydrogen bonds between ethanol and water allow the molecules to mix together and form a single, uniform solution. Therefore, option a) is the correct answer.