L1

Question 1

What is water?

Answer 1

Product of covalent bond between hydrogen (cation, +ive) and oxygen (anion, -ive)
H2OàH+ +OH-
(“free” protons, H+, actually react with H2O to make H3O+, which dissociates rapidly back to H2O + H+)
Kdissoc. = [(H+)(OH-) / (H2O)] = 10-14
“(X)” = “activity of X”
(activity) ≈ [concentration] in FW

Question 2

What does (__) mean vs [__}

Answer 2

( __ ) - this means activity
[ __ ] - this means concentration

In fresh water these are the same.
In sea water/brine/salt water lake, these become different.

And from here you begin to look at an equilibrium constant.

Question 3

Describe the molecular structure of water and ice…

Answer 3

Water is a POLYMER. When the molecule are near each other they align the positive and negative charges.
The dispersion of these can be mapped . The angles of alignment are generally very specific.

Question 4

Why does ice float?

Answer 4

Due to the ways that the molecules are organised they produce a greater volume that is less dense than the water.

Question 5

How is the structure of water mapped?

Question 6

What is the order of density of H2O states?

Answer 6

Least - Gas
Ice
Most - Water

There are 5 different density states that are related to temperature changes.

Question 7

What happens if ice forms on top of a body of water?

Answer 7

It insulates the water below, which allows for the water to remain in a liquid state

Question 8

Why do snowflakes have sixfold symmetry?

Answer 8

It is related to the structure and alignment of molecules within the polymer.

Question 9

Why might hot water freeze faster?

Answer 9

This is due to the molecules already being closer together and therefore more closely aligned.

Question 10

What is DISSOLUTION?

Answer 10

Simple dissolving.
dissolution via dissociation of a salt, e.g.
NaClàNa+ + Cl- CaCO3 à Ca2+ + CO32- PbCl2 à Pb2+ + 2Cl-

Different chemicals will dissolve at different rates.

Edges react faster as there is a line of imperfection.
Faces are the most stable.
Corners are the most uncommon.

Question 10

What are the 4 basic types of chemical reactions?

Answer 10

1.Dissolution
2.Hydrolysis
3. Reduction - Oxidation (‘redox’)
4.Dissolution without dissociation

Question 11

What is a salt?

Answer 11

in chemistry, substance produced by the reaction of an acid with a base. A salt consists of the positive ion (cation) of a base and the negative ion (anion) of an acid. The reaction between an acid and a base is called a neutralization reaction. The term salt is also used to refer specifically to common table salt, or sodium chloride. When in solution or the molten state, most salts are completely dissociated into negatively and positively charged ions and are good electrolytes (conductors of electricity). (Britannica)

Question 12

What is Hydrolysis?

Answer 12

The addition of water molecule(s).
Hydrolysis (English from hydro- + Greek lysis “a loosening, a dissolution,” from lyein “to loosen, dissolve”),
e.g.
CaCO3 + H2O –> Ca2+ + HCO3- + OH- CO2 + H2O –> HCO3- + H+
FeO + H2O –> FeOOH + H+ (Rust)

Question 13

What is the chemical formula of bicarbonate?

Answer 13

HCO3-

Question 14

What is the chemical formula of calcium carbonate?

Answer 14

CaCO3

Question 15

What is H+?

Answer 15

A proton

Question 16

What is a REDOX reaction?

Answer 16

reduction-oxidation (“redox”),
e.g. aA + bB + ne- –> cC + dD

Oxidation is loss of electrons. Reduction is gain of electrons. Oxidation and reduction occur ​simultaneously​in a reaction because one species loses electrons which are then donated and gained by the other species. Therefore they are known as redox​ reactions (​red​uction - ​ox​idation).

Question 17

What is Dissolution without dissociation?

Answer 17

Dissolution without dissociation,
e.g.
O2(g) –> O2(aq)
CH4(g) –> CH4(aq)

TDGP = total dissolved gas pressure
P(hydrostatic) = TDGP(max)

Question 18

Explain concentration units.

Answer 18

solvent = a liquid (or gas) that dissolves solids, gases or other liquids
solute = a substance dissolved by a solvent

molarity, M: (mass per Litre)
(g/L)(moles/g) = mol/L

molality, m: (mass per mass)
(g/kg)(moles/g) = mol/kg

ppm, ppb: (mass per mass)
(mg/kg), ug/kg

Question 19

What causes a phase?

Answer 19

The joining of species.

Question 20

Explain “Concentration” vs. “activity”

Answer 20

[A] = “concentration”; mass of solute A /
volume of water
When solution is dilute (i.e. freshwater),
[A] = “activity”, a, ofA
= (A) in molal

When ionic “strength” is “high,” C ≠ a

(solid) or (pure substance - pure O2) = 1
If there is more added to it, anything that is not pure yeilds a value of less than 1.

Here you begin to describe in regards to ionic strength

Activity allows you to talk about:
- ion size
- affinity for bonding

Question 21

What is an activity coefficient?

Answer 21

chemical activity = molality x activity coefficient

a = ym y = “gamma”

To compute a, must determine “ionic strength”, I:

I = 1/2 ∑ m (i) z 2(i)

m = molality of the “ith” ion
z = charge of the “ith” ion