# chemistry

posted by lisa

I have the answers, I am just interested in the formulas so that I can solve the problems, thanks!

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.

1. DrBob222

1. 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.

2. DrBob222

2. 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

3. DrBob222

3,5,5 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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