Chemistry Q4Amazing Benchmark

Review

Example 1:

Standard 9a: Know how to use Le Chatelier’s Principle to predict the effect of changes in concentration, temperature, and pressure.

Le Chatelier’s Principle

Le Chatelier’s Principle – when a change is imposed on a system at equilibrium, the position of the equilibrium shifts in a direction that tends to reduce the effect of that change

– This principle allows us to predict the effects of a system at equilibrium by changes in (1) concentration, (2) pressure, or (3) temperature.

– The goal is for the equilibrium to lie far to the right toward products.

Reactant(s) Product(s)

Example 2:

Standard 8a: Know the rate of reaction is the decrease in concentration of reactants or the increase in concentration of products with time.

Conditions That Affect Reaction Rates

1. Concentration – higher concentration of reactants lead to more collision

2. Temperature – speed of molecules increase with increase temperature, so the average collision is more energetic

Example 3:

Standard 8b: Know how reaction rates depend on such factors as concentration, temperature, and pressure.

Le Chatelier’s Principle

N2O4 (g) 2NO2 (g)

(Ea) CHANGE: SHIFT PREDICTION :

1. Addition of N2O4 Right

2. Addition of NO2 Left

3. Removal of N2O4 Left

4. Removal of NO2 Right

5. Decrease of container volume Left

6. Increase of container volume Right

7. Increase of temperature Right

8. Decrease of temperature Left

Example 4:

Standard 8c: Know the role a catalyst plays in increasing the reaction rate.

Conditions That Affect Reaction Rates

Catalyst (enzyme): a substance that speeds up a chemical reaction without being consumed (meaning it recycles)

Example 5:

Standard 9b: know equilibrium is established when forward and reverse reaction rates are equal.

Chemical Equilibrium: A Dynamic Condition

A chemical reaction has reached chemical equilibrium when the concentrations reach levels at which the rate of the forward reaction equals the rate of the reverse reaction.

Equilibrium (K)

Example 6:

Standard 11a: know protons and neutrons in the nucleus are held together by nuclear forces that overcome the electromagnetic repulsion between the protons.

Example 7

Standard 11b: know the energy release per gram of material is much larger in nuclear fusion or fission reactions than in chemical reactions. The change in mass (calculated by E = mc^2) is small but significant in nuclear reactions.

Example 7: Nuclear Fission

The decay of a single U-235 atom releases approximately 200 MeV (million electron volts). That may not seem like much, but there are lots of uranium atoms in a pound of uranium. So many, in fact, that a pound of highly enriched uranium as used to power a nuclear submarine is equal to about a million gallons of gasoline.

Example 8:

Standard 11c: know some naturally occurring isotopes of elements are radioactive, as are isotopes formed in nuclear reactions.

Example 8:

Naturally occurring Isotopes:

Isotopes from nuclear reaction:

Example 9

Standard 11d: know the three most common forms of radioactive decay (alpah, beta, and gamma) and know how the nucleus changes in each type of decay.

Alpha-particle production

Alpha (a) particle – produces helium (4/2He) nucleus – For example:

Types of Radioactive Decay: Number 1

• Net effect is loss of 4 in mass number and loss of 2 p+ in atomic number.

Beta-particle production

Types of Radioactive Decay: Number 2

• Net effect is to change a neutron to a proton. Thus; atomic number increase by 1.

• Beta (B) particle – releases electron (0/-1 e)

For example:

Gamma ray release

Types of Radioactive Decay: Number 3

• Gamma (Y) ray – release of 2 rays of high energy

photons and 1 alpha particle (4/2 He)

– For example: energy photons have no effect on element

Example 10

Standard 11e: know alpha, beta, and gamma radiation produce different amounts and kinds of damage in matter and have different penetrations.

Example 10:

Alpha: gets stopped by a few centimeters of air or a thin sheet of paper.  You may think that this means alpha radiation is quite weak but in fact the opposite is the case. Very Dangerous for atoms/cells! 20X more damaging than other rays—called ionization.

Beta: goes through a few meters of air and is stopped by a thin piece of lead. Less dangerous for atoms/cells. Example: X-rays.

Gamma: are like a wind blowing over our lawn. Gamma rays can pass through a thin sheet of lead with very little effect.  You need about 10 cm of lead to stop most gamma rays completely.

Example 11

Standard 10a: know large molecules (polymers), such as proteins, nucleic acids, and starch, are formed by repetitive combinations of simple subunits.

monomer polymers

Note: amino acid proteins

nucleotide nucleic acids

simple sugars starch

Polymers

• Polymers – large chainlike molecules made from many small molecules called monomers – Simplest polymer: polyethylene– Polymerization is the process in which monomers are

added together to form polymers.

Polymers

Condensation polymerization – a small molecule (often water) is released for each addition of a monomer to the polymer chain

– For example: Nylon

Example 12

Standard 10b: know the bonding characteristics of carbon that result in the formation of a large variety of structures ranging from simple hydrocarbons to complex polymers and biological molecules.

Carbon Chemistry

Carbon is an element that1. Can bond strongly to itself (C—C)2. Can form long chains or rings (C—C—C—C—C…)3. Can bond to other nonmetals: H, N, O, S, and

halogens.4. Thus, there are many types of carbon compounds

Biomolecule – molecule that functions in maintaining and reproducing life

Organic compounds – vast majority of carbon compounds

Alkanes

Alkanes are saturated hydrocarbons with tetrahedral structures with the general formula CnH2n+2 with n = 1, 2, 3, 4, 5….

CH4 C2H6 C3H8 C4H10

methane ethane propane butane

Alkanes

Example 13

Standard 10c: know amino acids are the building blocks of proteins.

Primary Structure of Proteins

amino acids (20 types) – building blocks of all proteins

• R groups (side chains) – may represent H, CH3 or more

complex substituents • Amino group (NH2) and carboxyl group (COOH) are

always attached to the carbon.

Structure of Proteins

Example 14

Standard 1a-n: know that the scientific process or method involves asking meaningful questions and conducting careful investigations.

Example 14