Chapter 28 - Solutions

Question 1

What is a solution?

Answer 1

A homogenous mixture of substances that combine to form a single phase, generally liquid in state

Question 2

What does a solution consist of?

Answer 2

A solute dissolved in a solvent

Question 3

Define solvation:

Answer 3

Interaction between solute and solvent
- Occurs when the attractive forces between solute and solvent are stronger than attractive forces between solvent particles

Question 4

Define hydration:

Answer 4

When water is the solvent and the resulting solution is called an aqueous solution

Question 5

What is the general rule of solvation?

Answer 5

Like dissolves like

- I.e. Polar dissolves polar; non-polar dissolves non-polar

Question 6

Define solubility:

Answer 6

The maximum amount of that substance that can be dissolved in a solvent at a particular temperature

Question 7

What types of solubility is there?

Answer 7

1) Saturated: Maximum amount of solute is added - if more is added it will not dissolve
2) Super-saturated: Dissolving more than the maximum solute by altering temperature or pressure
3) Crystallization: When dissolved solute comes out of solution and forms crystals

Question 8

How is electrical conductivity possible in aqueous solutions?

Answer 8

By the presence and concentration of ions in the solution

Question 9

What are electrolytes?

Answer 9

Solutes that make conductive solutions

• Considered a strong one if it dissolves completely into its constituent ions (NaCl, KI, highly polar covalent)
• Considered a weak one if it ionizes or hydrolyzes incompletely in solutions (acetic acid, ammonia, HgCl2)
• Non-electrolytes do not ionize at all in solutions which limits their solubility (non-polar gases, organic compounds, oxygen and sugar)

Question 10

What denotes the amount of solute dissolved in solvent? What is it expressed by?

Answer 10

Concentration

- Expressed by percent composition by mass, mole fraction (X), molarity (M), molality (m), and normality (N)

Question 11

What is percent composition by mass?

Answer 11

The mass of the solute divided by the mass of the solution x 100

PCbM = [Mass of Solute / Mass of Solution] x 100

Question 12

What is the percent composition by mass of NaCl of a saltwater solution if 100g of the solution contains 20g of NaCl (page328)?

Answer 12

20% NaCl solution

Question 13

What is mole fraction?

Answer 13

Mole fraction of a compound is equal to the number of moles of the compound divided by the total number of moles of all species within the system
- The sum will always equal 1

X = Moles / Sum of Moles of All Components

Question 14

If 92g of glycerol is mixed with 90g water, what will be the mole fractions of the two components (page 329)?

• H2O = 18g/mol
• C3H8O3 = 92g/mol

Answer 14

Water = 0.833
Glycerol = 0.167

= 1.000

Question 15

What is molarity?

Answer 15

The number of moles of solute per L of solution

- Depends on the total volunteer of the solution NOT the volume of solvent used to prepare the solution

Question 16

If not enough water is added to 11g of CaCl2 to make 100mL of solution, what is the molarity of the solution (page 329)?

Answer 16

1.0M CaCl2

Question 17

What is molality?

Answer 17

The number of moles of solute per kg of solvent

- For dilute aq solutions at 25C the molality is ~ equal to molarity because of density of water at this temperature

Question 18

If 10g of NaOH are dissolved in 500g of water, what is the molality of the solution (page 330)?
- NaOH = 40g/mol

Answer 18

0.50m NaOH

Question 19

What is normality?

Answer 19

Normality of a solution is equal to the number of gram equivalent weights of solute per L of solution
- Reaction dependant

N = M x (equiv/mol) = (mol/L) x (equiv/mol) = equiv/L

Question 20

What is dilution? What is the equation?

Answer 20

A solution is diluted when solvent is added to a solution of higher concentration to produce a solution of lower concentration

MiVi = MfVf

Question 21

How many mL of 5.5M NaOH solution must be used to prepare 300mL of a 1.2M NaOH solution?

Answer 21

65mL

Question 22

What are factors that affect solubility?

Answer 22

• Temperature
• Solvent
• Gas-phase solute
• Pressure
• Addition of other substances

Question 23

What are soluble salts?

Answer 23

• Salts of alkali metal ions (Li, Na, K, Rb, Cs, Fr)
• Salts of ammonium ion (NH4)
• Salts with Cl, Br, and I with the exception of Ag, Pb, and Hg
• Salts of sulfate ions (SO4) with the exception of Ca, Sr, Ba, Pb

Question 24

What are insoluble salts?

Answer 24

• Metal oxides (metal with oxygen) with the exception of CaO, SrO, BaO
• Hydroxides (OH) with the exception of Ca(OH)2, Sr(OH)2, and Ba(OH)2
• Salts with carbonates (CO3), phosphates (PO4), sulfides (S), and sulfites (SO3) with the exception of those that contain alkali metals or ammonium