Chemistry Term 4 Exam

1. Gases are made up of paticles moving with rapid, constant random motion

2. The higher the temperature, the faster the particles move. They have increased kinetic energy.

3. The forces of attraction and repulsion between the gas particles are pratically zero

4. The particles are very far apart. The volume of the particles is very small compared with the volume that the gas occupies

5. Particles collide with eachother and the walls of the container exerting pressure. The collisions with each other are perfectly elastic. This means that no kinetic energy is lost when they collide with eachother. 

Ideal Gas Law:

For an ideal gas (a gas that obey the kinetic molecular theory)                                                          PV=nRT                                                                                                                                                                         where R=8.31

Ideal vs Real Gases:

- Ideal gases obey the Gas Laws at specific temperatures and pressures                      - No gases obey these laws at all temperatures and pressures                                          - Real gases will not follow the gas laws at very high pressures or very low temperatures. This is  because the particles become closer together and take up more space, therefore forces exist between them.  

- The total pressure in a gas mixture is the sum of the partial of the partial pressures of each individual gas: 

Ptotal=P1+P2+P3...             

In the Human Body:

-Humans need a partial pressure of about 11kPa of 02 to survive but we cannot exceed 160kPa

Scuba Diving Example:

- Max Depth= (max pressure - PO2 / PO2 ) x10                                                                  - If we reduce the O2 and rmove N2 from the air and replace it with a non-toxic unreactive gas (helium) we can dive deeper                                                                        - At high pressures, increased amounts of nitrogen enter the blood. When a diver ascends rapidly, the nitrogen expands causing bubbling in the blood stream (the bend)                                                                                                                                             -Helium is less soluble in water than nitrogen and does not enter the bloodstrem. This is       because it diffuses at faster rate. 

-Diffusion is the tendency of gases to spread out. Effusion is when a gas escapes through a tiny hole in its container.                                                                                       -Graham's law of effusion shows that ligher gases effuse faster than heavier gas                   

Rate 1 =   /M2

 Rate 2 = /M1

Enthalpy:

-Enthalpy is the heat content of a system                                                                              -The change in enthalpy is given by:                                                                                ^H= H(products) - H(reactants)

Exothermic Reaction:

- Heat is released                                                                                                                      - ^H is negative                                                                                                                         - Feel hot

Endothermic Reaction:

- Absorb heat from surroundings                                                                                          - ^H is positive                                                                                                                            - Feels Cold

Heat Energy = mass of water x change in temp. x heat capacity of water                                                     ^H= mC^T                                                                                                                              where C= 4.18 J/g/c

- Respiration is the chemical reaction that occurs in our cells to provide energy           - It allows us to extract energy from food                                                                                                                             
- During aerobic (with oxygen) respiration our bodies use glucose to obtain energy

                                           6CO2 + C6H12O6 -> 6H2O + 6CO2      ^H = -2803 kJ/mol                                                                                                 
 glucose + oxygen -> water + carbon dioxide

-For sports that require short bursts of energy, anaerobic respiration occurs

                                                          C6H12O6 -> 2C3H6O3             ^H = -118 kJ/mol                                                                                              
 glucose -> lactic acid

- Lactic Acid builds up in muscles and creates muscle fatigue

- Enzymes are proteins that act as biological catalyst                                                       - Enzymes increase the rate of chemical reactions in living things                                 - They do not change the normal equilibrium position of a chemical system, it justs speeds up the reaction rate                                                                                                    - Enzymes function best at body temperature (37.5^oC) 

- In a reversible reaction, the conversion of reactants to products, and the conversion of products to reactants occur simultaneously                                                - When the rates of the forward and reverse reaction are equal, chemical equilibrium has been reached                                                                                                                                                                                                     

-Le Chatlier's principle states that if a change is applied to a system at equilibrium, the system reacts in such a way as to counteract the change, in order to return to equilibrium                                                                  

Changing Concentration:

- If more of a substance is added to a reaction, it will favour the side without that substance                                                                                                                                     - Conversely, if a substance is removed it will favour the side with that substance

Changing Temperature:

-Increasing the temperature of a system, will favour the with the least amount of heat                                                                                                                                               -Decreasingthe temperature of a system, will favour theside the heat is removed from

Changing Pressure:

- Increasing the pressure favours the the side with the least moles                                - Decreasing the pressure favours the side with the most moles

- Oxygen is transported around the body in blood by the complex molecule called haemoglobin 

Hb(aq) + O_{2 (aq)}    HbO_{2 (aq)}

-In our lungs the oxygen concentration is high and the reaction shifts to the right. When the blood reaches the tissue cells, there is a much lower oxygen concentration (due to respiration). In response to this the reaction moves to the left. Thus oxygen is moved around the body

Carbon Monoxide Poisoning:

- Carbon monoxide reacts with haemoglobin in the same way as oxygen:

Hb(aq) + CO _(aq)    HbCO _(aq)

-Carbon monoxide combines more strongly with hemoglobin than oxygen. The tissue cells will be starved of oxygen because carbon monoxide rather than oxygen is being transported                                                                                                                       - The suggested treatment is to give oxygen rich air 

Acids:

-Acids are hydrogen-containing compounds that ionise to yeild hydrogen ions (H+) in aqueous solution

-Properties: sour to taste, will dissolve in water, they are nautralised by bases

-Types of Acids: Monoprotic Acid: contains one ionisable hydrogen ion, Diprotic Acid: contains two ionisable hydrogen ions, Triprotic Acid: contains three ionisable hydrogen ions                                                                                           

- The strength of an acid depend on how many H+ ions are released. Strong acids are completely dissociated/ ionised.

-If the acid is less than 100% dissociated it is a weak acid. Weak acids are partially dissociated and therefore form few H+ ions.

-Ka is the acid dissociation constant. It is a quantative measure of the strength of an acid in a solution. It gives the ratio of the ionised form of acid to the ionised form

Ka= [products] / [reactants] 

- Bases are compounds that ionise to yield hydroxide ions (OH-) in aqueous solution.                                                                                                                                         - Strong bases produce lots of OH- ions                                                                     - Weak bases only produce a few OH- ions                                                                          - Bases neautralise acids                                                                                                                                

Kw:

-Kw, is the ion product or the dissociation constant of water. Water undergoes dissociation to a very small extent.

H2O <-> H+ + OH-

- The product of the concentrations of H+ ions and OH- ions is called the ion-product constant for water.

Kw= [H+] x [OH-] = 1 x 10^-14

-The Bronsted-Lowry theory defines an acid as a hydrogen donor and a base as a hydrogen acceptor

- A conjugate acid is the particle formed when base gains a hydrogen ion

- A conjugate base is the particle that remains when an acid has donated a hydrogen ion

- A conjugate acid-base pair consists of two substances related by the oss or gain of a single hydrogen ion

pH Calculations:

- pH= -log [H+]

- [H+]= 1x10^-7

pH Scale:

- Acidic Solution: pH < 7.0                                                                                                                  - Neutral: pH = 7.0                                                                                                                                                             - Basic: pH > 7.0

pOH Calculations:

- pOH= -log [OH-]

- pH + pOH =14

-There are 3 major reactions that acids can undergo:                                                               * Acid + Base                                                                                                                                * Acid + metal                                                                                                                               * Acid + Carbonate

Acid + Base Reaction:

- The acid/base reaction is called a neautralisation reaction                                                                            Acid + Base -> Salt + Water                                                                     -It is called neutralisation because:                                                                                                                                                     H+ + OH- -> H2O                                                        - In general, the reaction of an acid with a base produces water and one of a class of compounds called salts