Question

1- Consider the following substances: a polar solute and polar solvent. Explain the interactions of these and whether a solution will form. • H1 or HLE of Solute:

• H2 HLE of Solvent:

• H3 or HHYD:

• HSolution: Outcome

Options: a-Highly Endothermic b-Slightly Endothermic c- Highly Exothermic d-Slightly Exothermic

2- Consider the following compounds. Which is insoluble?

• VI2VI2

• HgBr2HgBr2

• NaBr

• NaCl

• All of these

• None of these

3- Select the conditions where liquid solutes have the highest solubility in water. Select those that USUALLY apply.

• Structural effects: The molecule should be .

• Agitation: Agitating the solution the solubility.

• Pressure: Solubility is highest when pressure is .

4- Ethanol has a Kb of 1.22 °C/m and usually boils at 78.4 °C. How many mol of an nonionizing solute would need to be added to 45.37 g ethanol in order to raise the boiling point to 82.8.

5- Water has a Kf of -1.86 °C/m. Calculate the new freezing point of an aqueous solution made by mixing 37.81 g water and 2.85 g MgCl2.

6- A solution contains 15.03 grams of NaCl in 0.557 kg water at 25 °C. What is the vapor pressure of the solution? (The vapor pressure of pure water is 23.7 torr at 25 °C.)

7- When a colloid separates by droplets becoming progressively bigger until they settle out it is called ________.

• flocculation

• coalescence

• creaming

8- When a colloid separates by one of the substances migrating to the top of the mixture it is called ________.

• coalescence

• flocculation

• creaming

9- How many mL of a 5 M HCl solution would it take to make a 250 mL of a 1.6 M solution? Give your answer to 1 decimal space.

10- What is the concentration of magnesium bromide, in ppm, if 55.3 g MgBr2 is dissolved in 9.24 L water. Record your answer in scientific notation to 3 significant figures.

11- How many mL of a 6.8 M HCl solution would it take to make a 250 mL of a 1.6 M solution?

• 0

• 0.4

• 1062.5

• 58.82

• 0.24

Answer 1

2. Insoluble one from the list is,

HgBr2

It is insoluble in water and precipitates out.

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3. Liquid solutes have highest solubility with,

-Structural effects - If it can form strong intermolecular bonds with solvent,

-agitating the liquid (mixes easily)

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4. From the data

elevation in boiling point dTb = 82.8 - 78.4 = 4.4 oC

dTb = iKbm

i = 1, Kb = 1.22 oC/m, m = moles solute/0.04537 kg EtOH

So,

moles solute = 4.4 x 0.04537/1 = 0.2 moles

We would add 0.2 moles of non-ionizing solute to raise boiling point.

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5. molallity of solution = moles of solute/kg of solvent

                                    = 2.85 g/95.21 g/mol x 0.03781 kg

                                    = 0.8 m

Depression in freezing point dTf

dTf = -iKfm

i = 3 (Van;t hoff factor)

Kf = -1.86 oC/m

m = 0.8 m

So,

dTf = -3 x 1.86 x 0.8 = 4.464 oC

new freezing point = 0 - 4.464 = -4.464 oC

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6. moles of NaCl = 15.03 g/58.4 g/mol = 0.26 mol

moles of H2O = 0.557 kg x 1000/18 g/mol = 31 mol

mole fraction of water = 31 mol/31.26 mol = 0.992

vapor pressure of solution = vapor pressure of pure water x mole fraction of water

                                          = 23.7 torr x 0.992

                                          = 23.51 torr

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7. When colloids separated by smaller particles becoming larger ones are,

coalescence

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8. When a colloid separates, it is called,

flocculation

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9. Using, C1 = C2.V2/C1

with, C1 = 5.0 M, C2 = 1.6 M, V2 = 250 ml

ml of 5.0 M HCl needed (V1) = 1.6 M x 250 ml/5.0 M = 80.0 ml

Answer, 80.0 ml

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10. mg of MgBr2 = 55.3 g x 1000 = 55300 mg

volume of solvent = 9.24 L

ppm = mg/L

Therefore,

coccentration of solution in ppm = 55300 mg/9.24 L = 5984.848 ppm (598 x 10^1 ppm)

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11. Using, C1 = C2.V2/C1

with, C1 = 6.8 M, C2 = 1.6 M, V2 = 250 ml

ml of 6.8 M HCl needed (V1) = 1.6 M x 250 ml/6.8 M = 58.82 ml

Answer, 58.82 ml