Monday, January 29, 2007
Monday, Day 5
AP: we waded through the Spec-20 Absorbance to Concentration Data problem. Sorry I didn't anticipate the mental gymnastics required to make the data "work"; on the other hand, sometimes it is good to figure things out on the fly.
We finished kinetics by discussing how the Arrhenius equation relates the rate constant to the activation energy for a reaction; that is, the higher the activation energy for a given reaction, the LOWER the rate constant; HOWEVER, you CANNOT say that those variable are simply inversely proportional because they do not follow the equation xy=constant (or k x Ea = constant). Just say that, as one increases, the other decreases, good enough.
We then began our long journey into equilibrium by defining the term, noting that equilibrium NEVER EVER EVER means equal CONCENTRATIONS of reactants and products (never has been, never is, never will be); equilibrium CAN and MUST only pertain to equal RATES of forward and reverse processes or reactions.
We saw that, for varying initial concentrations of reactants and products, the equilibrium concentrations will ALSO vary. HOWEVER, there is a way to arrange the equilibrium concentration values in a certain ratio such that the ratio is a constant no matter what the initial reactant and product concentrations were (assuming the same Temperature for each experiment). We call that "arrangement" of the reactant and product concentrations, the EQUILIBRIUM CONSTANT EXPRESSION, which is the concentrations of the products to their respective coefficients (from the balanced equation) divided by the concentrations of the reactants to their respective coefficients.
Tomorrow's exam will cover the whole kinetics unit and will involve more calculations than explanations. There will also be a descriptive chem set of 5 questions with labeling of reaction type as well as balancing.
Honors: we balanced several equations and practiced how to balance equations that result in a non-integer coefficient for a reactant or product; we ended up just multiplying the entire equation by whatever number is in the denominator of the fraction (non-integer).
We then reviewed five types of chemical reactions by showing what they generally look like.
After that, we began calculations of gram-atomic mass, gram-molecular mass, and gram-formula mass of elements and compounds, respectively. These calculations are really the basis and heart of this unit so practice them on the posted worksheets.
There is a test on WEDNESDAY, covering the stated online objectives as well as chemical reaction types and balancing.
Regents: we finished our lab test review; corrections from that test are due on Thursday. I hope that you are now much more familiar and comfortable with that material and with your new seats (let me know if you have trouble seeing the screen from your new vantage point).
We then reviewed vapor pressure and normal boiling points relative to the strength of the intermolecular attractions. The STRONGER the intermolecular force of attraction, the LOWER the vapor pressure at a given temperature, and also the higher the normal boiling point of the substance.
We also reviewed electrolytes ( acids, bases, and soluble salts) and non-electrolytes (all molecules except for acids).
We will definitely finish the unit tomorrow and start on the Math of Chemistry. It is VERY important that you ALREADY know how to name compounds before we start this unit.
There is a test on THURSDAY covering the bonding unit objectives that were posted over the weekend. The test will emphasize intermolecular attractions and physical properties that are caused by the degree of intermolecular attractions.
We finished kinetics by discussing how the Arrhenius equation relates the rate constant to the activation energy for a reaction; that is, the higher the activation energy for a given reaction, the LOWER the rate constant; HOWEVER, you CANNOT say that those variable are simply inversely proportional because they do not follow the equation xy=constant (or k x Ea = constant). Just say that, as one increases, the other decreases, good enough.
We then began our long journey into equilibrium by defining the term, noting that equilibrium NEVER EVER EVER means equal CONCENTRATIONS of reactants and products (never has been, never is, never will be); equilibrium CAN and MUST only pertain to equal RATES of forward and reverse processes or reactions.
We saw that, for varying initial concentrations of reactants and products, the equilibrium concentrations will ALSO vary. HOWEVER, there is a way to arrange the equilibrium concentration values in a certain ratio such that the ratio is a constant no matter what the initial reactant and product concentrations were (assuming the same Temperature for each experiment). We call that "arrangement" of the reactant and product concentrations, the EQUILIBRIUM CONSTANT EXPRESSION, which is the concentrations of the products to their respective coefficients (from the balanced equation) divided by the concentrations of the reactants to their respective coefficients.
Tomorrow's exam will cover the whole kinetics unit and will involve more calculations than explanations. There will also be a descriptive chem set of 5 questions with labeling of reaction type as well as balancing.
Honors: we balanced several equations and practiced how to balance equations that result in a non-integer coefficient for a reactant or product; we ended up just multiplying the entire equation by whatever number is in the denominator of the fraction (non-integer).
We then reviewed five types of chemical reactions by showing what they generally look like.
After that, we began calculations of gram-atomic mass, gram-molecular mass, and gram-formula mass of elements and compounds, respectively. These calculations are really the basis and heart of this unit so practice them on the posted worksheets.
There is a test on WEDNESDAY, covering the stated online objectives as well as chemical reaction types and balancing.
Regents: we finished our lab test review; corrections from that test are due on Thursday. I hope that you are now much more familiar and comfortable with that material and with your new seats (let me know if you have trouble seeing the screen from your new vantage point).
We then reviewed vapor pressure and normal boiling points relative to the strength of the intermolecular attractions. The STRONGER the intermolecular force of attraction, the LOWER the vapor pressure at a given temperature, and also the higher the normal boiling point of the substance.
We also reviewed electrolytes ( acids, bases, and soluble salts) and non-electrolytes (all molecules except for acids).
We will definitely finish the unit tomorrow and start on the Math of Chemistry. It is VERY important that you ALREADY know how to name compounds before we start this unit.
There is a test on THURSDAY covering the bonding unit objectives that were posted over the weekend. The test will emphasize intermolecular attractions and physical properties that are caused by the degree of intermolecular attractions.
# posted by C @ 10:11 AM 
