2.A student was required to make a solution of camphor and naphthalene that had afreezing point of 166 C. How many grams of naphthalene (CjoHs) need to be addedto 10.0 g of camphor to make this solution? The freezing point of pure camphor is178.4°C and the freezing point depression constant for camphor, Kf, is 37.7°C/m.3. The freezing point of biphenyl (molar mass 154 g/mole) is 71.0°C. When 1.240 g ofbenzophenone (molar mass 182 g/mole) is added to 9.52 g of biphenyl the solution isfound to freeze at 14.3°C. Calculate the freezing point depression constant, Ks, forbiphenyl.4. You are given a vial with an unknown compound. You are told that it is a sodium halidecompound. You need to determine the identity of the halide. When 1.57 g of NaX is addedto 39.2 g of distilled water, the resulting solution was cooled and the freezing point wasdetermined to be -1.45°C. What is the identity of X? (Assume the freezing point of thedistilled water is 0.00°C.)140

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Asked Feb 2, 2019
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2.
A student was required to make a solution of camphor and naphthalene that had a
freezing point of 166 C. How many grams of naphthalene (CjoHs) need to be added
to 10.0 g of camphor to make this solution? The freezing point of pure camphor is
178.4°C and the freezing point depression constant for camphor, Kf, is 37.7°C/m.
3. The freezing point of biphenyl (molar mass 154 g/mole) is 71.0°C. When 1.240 g of
benzophenone (molar mass 182 g/mole) is added to 9.52 g of biphenyl the solution is
found to freeze at 14.3°C. Calculate the freezing point depression constant, Ks, for
biphenyl.
4. You are given a vial with an unknown compound. You are told that it is a sodium halide
compound. You need to determine the identity of the halide. When 1.57 g of NaX is added
to 39.2 g of distilled water, the resulting solution was cooled and the freezing point was
determined to be -1.45°C. What is the identity of X? (Assume the freezing point of the
distilled water is 0.00°C.)
140
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2. A student was required to make a solution of camphor and naphthalene that had a freezing point of 166 C. How many grams of naphthalene (CjoHs) need to be added to 10.0 g of camphor to make this solution? The freezing point of pure camphor is 178.4°C and the freezing point depression constant for camphor, Kf, is 37.7°C/m. 3. The freezing point of biphenyl (molar mass 154 g/mole) is 71.0°C. When 1.240 g of benzophenone (molar mass 182 g/mole) is added to 9.52 g of biphenyl the solution is found to freeze at 14.3°C. Calculate the freezing point depression constant, Ks, for biphenyl. 4. You are given a vial with an unknown compound. You are told that it is a sodium halide compound. You need to determine the identity of the halide. When 1.57 g of NaX is added to 39.2 g of distilled water, the resulting solution was cooled and the freezing point was determined to be -1.45°C. What is the identity of X? (Assume the freezing point of the distilled water is 0.00°C.) 140

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Expert Answer

Step 1

Freezing point is a colligative property, meaning it depends upon the amount of solute or ion present in solution.

Step 2

2. Given here we have to prepare a solution of naphthalene in camphor.

mass of capmphor = 10 g = 0.010 kg

[1 kg = 1000 g]

freezing point of pure camphor = 178.4 degree C

freezing point of solution after mixing naphthalene = 166 degree C

Depression in frezing point (dTf) = 178.4 - 166 = 12.4 degree C

Freezing point constant for Camphor = 37.7 degree C/m

Using,

dTf = freezing point constant x molality of solution

12.4 = 37.7 x molality of solution

molality of solution = 0.33 m

with,

molality = moles of solute/kg of solvent

moles of naphthalene added = 0.33 m x 0.010 kg = 0.0033 mols

with,

mol...

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