Unit 4 Solutions

Question 1

How can a supersaturated solution be achieved?

Answer 1

Can be achieved when water is heated and allowed to dissolve as much solute as possible. Then the temperature is carefully reduced. However is distured, the excess solute will precipitate out.

Question 2

What’s ratio of solute is classified as soluble in water?

Answer 2

A substance is considered to be soluble in water if more than 1 g can be dissolved in 100 mL of water

Question 3

A substance is considered to be insoluble in water for what ratio of solute to solvent?

Answer 3

A substance is considered to be insoluble in water if less than 0.1 g can be dissolved in 100 mL of water

Question 4

Slightly soluble substances have how much solute in solvent?

Answer 4

any amount in between 0.1-1g in 100mL

Question 5

Factors that affect dissolving/solubility are…

Answer 5

Temperature
- Increasing temperature increases speed of solvent molecules
- They collide with the solute molecules more often and with greater force
The solute is broken down faster
Surface area of solute
- More surface area results in more contact between solute and solvent molecules
Agitation
- Solvent molecules are moved toward undissolved solute molecules

Question 6

If temperature increase how does it affect the three states when they dissolve?

Answer 6

• More solid will dissolve
• Same amount of liquid will dissolve
• Less gas will dissolve (gases able to evaporate)

Question 7

When pressure increases, how does it affect the gas when dissolving?

Answer 7

the increase of pressure dissolves more gas

Question 8

Solutions form because it’s more energetically favorable for the __ molecules to be surrounded by ___ molecules than to be separated.

Answer 8

solute, solvent

Question 9

In insoluble, substances have what forces that causes them to be insoluble?

Answer 9

Intermolecular forces between solute particles are greater than forces between solute and solvent

Question 10

In soluble, substances have what forces that causes them to be soluble?

Answer 10

Intermolecular forces between solute particles are less than forces between solute and solvent

Question 11

What are the two bonds that break when a solution is formed? And once formed, is energy absorbed or released?

Answer 11

1.Separation of the solute molecules (Breaking bonds requires energy)
2. Separation of some solvent molecules (Breaking intramolecular bonds requires energy)
3. Formation of solute-solvent bonds (Energy released as bonds form)

Question 12

What is the formula for calculating pH?

Answer 12

pH = -log[H+]

Question 13

What is a strong acid?

Answer 13

An acid that completely ionizes in water

Question 14

What is a weak acid?

Answer 14

An acid that only ionizes partially in water

Question 15

What is the pH of pure water at 25°C?

Answer 15

7

Question 16

Fill in the blank: A solution with pH less than 7 is _______.

Answer 16

acidic

Question 18

What is the relationship between [H+] and [OH-] in a neutral solution?

Answer 18

[H+] = [OH-]

Question 19

What does autoionization of water refer to?

Answer 19

The process where water molecules dissociate into hydrogen ions and hydroxide ions

Question 20

True or False: Chloric acid is a strong acid.

Answer 20

True

Question 21

What is the concentration of hydrogen ions in pure water?

Answer 21

1.0 x 10^-7 M

Question 22

Types of Intermolecular Forces (Strongest to Weakest)

Answer 22

1. Ion-dipole forces
2. Hydrogen bonding (special case of dipole-dipole force)
3. Dipole-dipole Forces
4. Dispersion Forces (aka London forces)
   (The last two are also known as van der Waals forces)

Question 23

Ion-Dipole forces

Answer 23

• Between an ion and a polar molecule (dipole)
• The strength of these forces is what makes it possible for ionic substances to dissolve in polar solvents
• Ionic cations are attracted to the negative pole and anions are attracted to the positive pole

Question 24

hydrogen bonding

Answer 24

• Solubility in water is influenced by hydrogen bonding
• Occurs when H atoms bond to N, O, or F
• Unusually very strong this can be explained by the small atomic size and high electronegativity of N, O and F
• Dipole–dipole interactions
• Hydrogen bonds are between molecules

Question 25

Dipole-Dipole

Answer 25

Between two polar molecules (Two Dipoles) - The oppositely charged ends attract each other.

Question 26

London (dispersion) forces

Answer 26

Nonpolar particles can be temporarily polarized to allow dispersion force to form. The tendency of an electron cloud to distort is called its polarizability.

Question 27

Solubility of molecular compounds in water is dependent on the ____ of the molecules

Answer 27

polarity, because like dissolves like. Since water is always the solvent, if the the solute is also polar, then it's soluble.

Question 28

Non-polar molecules have low solubility in water. Why?

Answer 28

-Little energy is needed to separate non-polar molecules. London Forces are weak. -Requires a significant amount of energy to break H-bonds between water molecules - Intermolecular forces between water and non-polar molecules are weak.

Question 29

Polar molecules are generally soluble in water. Why?

Answer 29

- More energy is required to separate molecules held together by dipole-dipole force -Stronger intermolecular forces form between polar molecules and water molecules (dipole-dipole forces or hydrogen bonds

Question 30

Dissolving Ionic Compounds

Answer 30

- The bonding force in ionic compounds is the electrostatic force between ions. - Water molecules are bound to each other by strong hydrogen bonds. - Ions which separate from the salt are surrounded by water molecules - Some compounds with strong ionic bonds are not soluble. (ex. AgCl)

Question 31

Solubility graphs show....

Answer 31

- Shows change in solubility with temperature. - Solids generally increase solubility with temperature - Liquids have smaller changes, but generally become less soluble.

Question 32

why are aluminum less reactive, or at least they appear so?

Answer 32

this is due to the oxide coating it forms.

Question 33

Evident of a double displacement...

Answer 33

- formation of a precipitate - formation of gas - neutralisation reactions

Question 34

What's an example of indirect formation of gas?

Answer 34

➢ Indirect formation of a gas 𝑀𝑔𝐶𝑂3 𝑎𝑞 + 𝐻2𝑆𝑂4 𝑎𝑞 ⟶ 𝑀𝑔𝑆𝑂4 𝑎𝑞 + 𝐻2𝐶𝑂3(𝑎𝑞) Carbonic Acid (𝐻2𝐶𝑂3) is unstable and decomposes to form CO2 𝐻2𝐶𝑂3 𝑎𝑞 ⟶ 𝐻2𝑂 𝑙 + 𝐶𝑂2(𝑔)

Question 35

neautralisation reactions always produce what?

Answer 35

a salt + water

Question 36

true or false: all double displacement reaction substances are in the state or aquesous

Answer 36

true

Question 37

if pressure increase does the volume increase?

Answer 37

no

Question 38

what has weaker intermolecular force? Hydrogen bonding, temporary dipole?

Answer 38

temporary dipole

Question 39

True of False: gases expand and liquids expand as temp increase.

Answer 39

True. Although liquids expanded a little

Question 40

What' volume of 40.2g of K at STP?

Answer 40

11.2L

Question 41

What volume of O2 at STP is required to react with 10g K?

Answer 41

2.9 + O2 --> K20

Question 42

If temperature is doubled, and the moles is doubled, how much is the pressure increased by?

Answer 42

four times

Question 43

How to calculate the total pressure in a container?

Answer 43

you add them up, using the dalton's partial pressure