Tuesday

January 27, 2015

January 27, 2015

Posted by **lisa** on Tuesday, April 15, 2014 at 11:20pm.

1. Find the boiling point of a solution composed of 110g of HgCl2 (a non-ionizing solute) in 175g of water.

2. Find the freezing point of a solution composed of 50g IBr in 120 g of water. Assume 100% ionization. KBr = k1+Br1-.

3. Find the freezing point of solution composed of 74.15g MG(NO3)2 in 90 g of water. Assume 100% ionization.

4. Calculate the freezing point of a solution containing 12.0g of sucrose (C12H22O11) in 120g of water.

5. Calculate the boiling point of a solution containing 42.00 g of CuSO4 in 300g of water. CuSO4=Cu2+ + SO42-.

6. Find the molecular mass of a non-ionizing solute if 72g dissolved in 300g of water raise the boiling point to 100.860 degrees Celsius.

7. Find the molecular mass of a non-ionizing solute if 87.85g dissolved in 500g of water lower the freezing point to -3.00 degrees Celsius.

- chemistry -
**DrBob222**, Tuesday, April 15, 2014 at 11:32pm1. Find the boiling point of a solution composed of 110g of HgCl2 (a non-ionizing solute) in 175g of water.

mols HgCl2 = grams/molar mass

Substitute and solve for mols.

molality = m = mols/Kg solvent

Substitute and solve for m

delta T = i*Kb*m

Your post says i = 1

Kb = 1.51

Substitute and solve for delta T, then add to 100 C to find the new boiling point.

- chemistry -
**DrBob222**, Tuesday, April 15, 2014 at 11:36pm2. Find the freezing point of a solution composed of 50g IBr in 120 g of water. Assume 100% ionization. KBr = k1+Br1-.

I assume you made a typo and IBr really is KBr.

mols KBr = grams/molar mass.

Solve for mols.

molality = m = mols/kg solvent

Solve for m

delta T = i*Kf*m

i for KBr = 2

Kf = 1.86

Solve for delta T and subtract from 0 C to find the new freezing point.

delta T = i*Kf*m

i = 1

- chemistry -
**DrBob222**, Tuesday, April 15, 2014 at 11:39pm3,5,5 look just like 1 and 2.

6 and 7 are done by working backward.

delta T = i*Kf or Kb *m

You're given delta T, solve for m.

Then m = mols/kg solvent.

Solve for mols

Then mols = grams/molar mass. You're given mols and grams; solve for molar mass.

i = 1 for both 6 and 7

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