solutions

solution composition

100

What is the role of the solvent in a solution?

The solvent is the component that dissolves the solute and usually makes up the largest proportion of the solution. It provides the medium in which the solute particles disperse.

200

Explain the difference between a solute and a solvent.

• Solute: The substance that is dissolved (usually present in a smaller amount).
• Solvent: The substance that does the dissolving (usually present in a larger amount).

Example: In saltwater, salt is the solute, and water is the solvent.

300

How do hydrophilic and hydrophobic substances differ in their interaction with water?

• 
  

• Hydrophilic substances (“water-loving”) interact well with water because they are polar or can form hydrogen bonds. Examples: sugar, salts.
• Hydrophobic substances (“water-fearing”) do not mix well with water because they are nonpolar and cannot form hydrogen bonds. Examples: oils, fats.

400

A weak electrolyte exists predominantly as __________ in solution.

A) atoms   B) ions   C) molecules   D) electrons   E) an isotope

C) molecules

FACTORS AFFECTING SOLUBILITY

100

How does the structure of a molecule affect its solubility?

• Polar molecules dissolve well in polar solvents (like water) due to dipole interactions and hydrogen bonding.
• Nonpolar molecules dissolve better in nonpolar solvents (like oil) because of London dispersion forces.
  Rule: “Like dissolves like.”
  Functional groups (e.g., –OH, –NH₂) increase polarity and hydrogen bonding, improving water solubility.

200

Why does the solubility of gases typically decrease with increasing temperature?

As temperature rises, gas molecules gain kinetic energy and escape from the liquid phase more easily. This reduces their solubility.
Example: Warm soda loses carbonation faster than cold soda.

300

Describe how pressure affects the solubility of gases in liquids.

Higher pressure increases gas solubility because more gas molecules are forced into the liquid phase

400

Explain Henry’s Law in terms of gas solubility.

At a constant temperature, the amount of gas that dissolves in a liquid is directly proportional to the partial pressure of that gas above the liquid.

COLLIGATIVE PROPERTIES

100

How does the addition of a non-volatile solute affect the boiling point of a solvent? and why ? 

Adding a non-volatile solute raises the boiling point of the solvent. This happens because the solute lowers the solvent’s vapor pressure, so a higher temperature is needed for the vapor pressure to equal atmospheric pressure

200

Explain the concept of freezing point depression.

Freezing point depression occurs when a solute is added to a solvent, causing the freezing point to drop. The solute disrupts the formation of the solid phase (crystal lattice), so the solution must be cooled further to freeze.
Example: Salt added to water lowers its freezing point, which is why salt is used on icy roads.

300

What equation relates boiling point elevation to molality?

The equation is:
ΔT_b= i⋅K_b⋅m

400

What is the expected boiling point of a solution of 128 g KCl (a strong electrolyte) dissolved in 1.3 kg

of water. The molar mass of KCl is 74.55 g and Kb = 0.51C/m.

a. 98.7C

b. 99.5C

c. 100.7C

d.101.3C

d.101.3C

CONCENTRATION OF SOLUTION

100

Circle all of the following (more than one)  that are weak electrolytes?

  1) HCl  

2)  NH3  

3) CH3COOH   

4) KCl

2)  NH3         3) CH3COOH

200

There are __________ mol of bromide ions in 0.500 L of a 0.300 M solution of AlBr3 .

A)0.150   B) 0.0500   C) 0.450   D) 0.167  

E) 0.500

C) 0.450

300

What are the respective concentrations (M) of Na+  and SO4  ions orded by dissolving 0.500 mol of sodium sulphate    in water and diluting to 1.33 L?

A)0.665 and 0.665           

B) 0.665 and 1.33  

C) 1.33 and 0.665             

 D) 0.376 and 0.752                 

E) 0.752 and 0.376

C) 1.33 and 0.665

400

The total concentration of ions in a 0.250 M solution of HCl is __________.

A) essentially zero.   B) 0.125 M   C) 0.250 M   D) 0.500 M   E) 0.750 M

D) 0.500 M