Formation of Solutions

Chapter 12: Solutions

12.1 Solutions

12.2 Electrolytes and Nonelectrolytes

12.3 Solubility

A solution is a homogeneous mixture in which on substance, the solute, is uniformly dispersed in another substance, the solvent.

Usually the solute is present in lesser amount than the solvent.

Multiple Choice

Identify the solute when 10.0 g of NaCl and mixed with 100.0 g of H₂O.

• NaCl

• H₂O

Multiple Choice

Identify the solvent when 50.0 mL of ethanol is mixed with 10.0 mL of H₂O.

• ethanol

• H₂O

Formation of Solutions

• Interactions between a solvent (eg. water) and the solute determine whether a solution will form.

• Initially, energy is needed (endothermic) to separate the particles of the solute and the particles of the solvent.

• Then, energy is released (exothermic) as solute particles move between the solvent particles to form a solution.

• THERE MUST BE ATTRACTION BETWEEN THE SOLUTE AND SOLVENT FOR THE INITIAL SEPARATION.

"LIKE DISSOLVED LIKE"

THERE MUST BE ATTRACTION BETWEEN THE SOLUTE AND SOLVENT FOR THE INITIAL SEPARATION.

These attractions occur when the solute and solvent have similar properties.

• Polar solvents tend to form solutions with polar solutes.

• Nonpolar solvents tend to form solutions with nonpolar solutes.

In the absence of attractions between solvent and solute, there is insufficient energy to form a solution.

​Solubility

• Every solvent has a limit to how much of a solvent it can dissolve

• Solubility: the amount of solute that can be added to a solvent in specific conditions

  • Three types of solutions

    • Unsaturated: the solution contains less than the maximum amount of solute

    • Saturated: The solution contains the exact amount of solute

    • Super Saturated: The solution contains more than the maximum amount of solute

      • Extra solute crystalizes in the container

Experience Chemistry | Lesson 4.6

Drag and Drop

Water is a polar solvent and carbon tetrachloride is a nonpolar solvent. In which solvent is each of the following more likely to be soluble?




CaCO₃

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vitamin A (nonpolar)

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sucrose (polar)

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cholesterol (nonpolar)

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Drag these tiles and drop them in the correct blank above

water

carbon tetrachloride

​Solutions with Ionic and Polar Solutes

When ionic solutes, such as NaCl, are placed in water, the solvent, the ions become hydrated as the water molecules surround the ions as in the figure.

The equation for formation of this solution:

The polar molecular compound, methanol, is soluble in water because the polar -OH group forms hydrogen bonds with water.

​

Multiple Choice

Iodine is soluble in water.

• True

• False

What is an electrolyte?

• Substance that give separates into its ions when dissolved in water, which are able to conduct electricity.

• In order for a solution to be considered an electrolyte it must consist of both POSITIVE and NEGATIVE ions.

Multiple Choice

Which of the following best describes the components and properties of electrolytes? Electrolytes consist of –

• ions and are conductive

• metals and are non-polar

• nonmetals and are anions.

• covalent bonds and are polar

Multiple Choice

Which of the following, when dissolved in water, would create a nonelectrolyte?

• C₂H₆O

• NH₄NO₃

• NaOH

• BaCl₂

Dissociates but mostly molecules.

Weak electrolyte

100% dissociation.

Strong electrolyte

Electrolytes

Nonelectrolyte

If a compound dissolves in water only as molecules, it is a nonelectrolyte. An example of this is methanol in water.

CH₃OH(l) --> CH₃OH(aq)

Multiple Choice

KF is a strong electrolyte and HF is a weak electrolyte. How is the solution of KF different from that of HF?

• KF dissociates completely and HF only partially.

• KF dissociates only partially and HF dissociates completely.

• Both KF and HF dissociate completely, but KF is more toxic.

• Both KF and HF dissociate partially, but KF is more toxic.

Multiple Choice

NaOH is a strong electrolyte and CH₃OH is a nonelectrolyte. How is the solution of NaOH different from that of CH₃OH?

• NaOH dissociates completely and CH₃OH only partially.

• NaOH dissociates completely and CH₃OH not at all.

• NaOH does not dissociate at all while CH₃OH dissociates completely.

Draw

Write a balanced equation for the dissociation of the strong electrolyte, iron (III) nitrate.

​Factors that influence solubility

How much solute dissolves in a solvent depends on several factors:

• Polarity

• Temperature

• Pressure

​At T increases, more gas molecules have the energy to escape from solution.

Multiple Choice

At approximately what temperature does the solubility of sodium chloride, NaCl, match the solubility of potassium dichromate, K₂Cr₂O₇?

• 60 ºC

• 30 ºC

• 50 ºC

• 83 ºC

Multiple Choice

How many grams of K₂Cr₂O₇, are soluble in 100 g of water at 90 ºC?

• 85 grams

• 70 grams

• 40 grams

• 15 grams

Multiple Choice

Which substance is MOST soluble at 0 ºC?

• KI

• NaNO₃

• NaCl

• Ce₂(SO₄)₃

Henry's Law

​The solubility of a gas in a liquid is directly related to the pressure of gas above the liquid.

​Solubility α Pressure