Hess’s Law and Hof [aka heats of formation]
**technical difficulties abound with little delta symbols and superscripts and subscripts - do you know how to include symbols, superscripts and/or subscripts?



With Hess’s law – use each of the given equations, add to arrive at the target equation
-if the equation is reversed, the sign of H is also reversed (+ to – and/or – to +)
-if the equation is multiplied by a value, multiply H by the same value

One more thing, consider the equation written below:

4CO2 (g) + 6 H2O(g) -->2 C2H6 (g) + 7 O2 (g)            H = 849.0KJ

the molar enthalpy of CO2: HCO2 = 212.25 kJ/mol        [849kJ / 4 mol]

Any equation can be interpreted per mole of any substance in the equation

Heats of Formation Hof

-be able to write the formation reaction for any substance [produce one mole of product from elements in their standard state]

-when calculating H with heats of formation (data tbl 799-800) remember that it is:

                 (products) – (reactants)

For a small change a few elephant jokes. Ready or not, here they come. Q: How do elephants communicate? [On the elephone.]  Q: Why are elephants large, grey and wrinkled? [Have you ever tried ironing one?]  What time is it when an elephant sits on your fence? [Time to get a new fence.]

Day 4 - Food Snackfood Burning

A few snackfood burning lab write-up tidbits:
-word processed - [use a decent sized font - please :<)]
-include a copy (real or reasonable reproduction) of the nutrition label
-follow along with the calculations as outlined on the assignment handout (hint, hint - using p320 #4(eicosane) as a guide for several aspects of the calculation - Did you read the posting from Day 3?)
-include the assignment sheet (its green) with the final submission
-joules to food calories (Cal as opposed to cal)
http://health.howstuffworks.com/health-illness/wellness/physical-fitness/weight-loss/calorie1.htm

Additional items to include
-include a cheesy joke in the footer (optional - but appreciated)

This colour of font was selected because of the cheesy nature of the following joke. Two antennas met on a roof, fell in love and got married. The ceremony wasn't much, but the reception was excellent.  [In this age of digital/satellite cable, this joke is definitely from another era. If in doubt about its humour, share it with the parental figures. :<]

Energy Day 3 - Representing Enthalpy Change

Four ways to represent enthalpy changes are to be considered.
-see the four ways outlined on page 319 of Nelson Chemistry 12

A nice review of thermochemical equations is found at"
http://chemistry.about.com/od/physicalchemistrythermo/a/thermochemlaws.htm

This next link has some questions with answers - available after you answer the question. The answer does not require units, but include a negative sign if required. One other tidbit for the questions, you need to ensure that you have calculated the molar enthalpy of the substance of interest. [That is, you may need to divide the stated enthalpy of the equation by the moles (coefficient) associated with the desired reactant.]
http://chemistry.csudh.edu/lechelpcs/thermoequationscsn7.html

From today: Page 319-320 [2,3,4,5]  and page 320 [1 to 4]

A helpful hint for #4 page 320 (the eicosane question), the surroundings that are heated as a result of the burning candle are the copper container and the water in the copper container.
So -      nH combustion eicosane = -[mcTwater  +  mcTcopper]   ...once again, 'delta' represented by 

One other thing with this question - in (d) a percentage error calculation is requested - consider the %difference calculation outlined on page 778 of Nelson Chemistry 12. [% difference/ % error - the calculation will work for both. In this case the predicted value = actual value = -13.3 MJ  ...watch the units]

Now should you have to use a similar approach with a 'tin can' (~ iron) and a burning cheesie/chip/marshmallow/peanut/cracker......all the better. :<)

A few closing thoughts in honour of the potential cheesie burn - some cheesie jokes: (1) What do you call a fish with no eyes? A fsh  (2) I went to buy some camouflage trousers the other day but I couldn't find any.   (3) And finally, there was the person who sent twenty different puns to his friends, with the hope that at least ten of the puns would make them laugh.     No pun in ten did.

Day 2 of Energy - Enthalpy & Molar Enthalpy

-once again, no 'delta' symbol appears - for now it is just a 
(I haven't figured out the delta symbol part yet :<(

Two equations to consider

(1) H = nHx     or  (2) nHx = -mcT

where n - moles of system substance;   Hx  - molar enthlapy;    H  - enthalpy/ heat


If the question mentions the surroundings
- typically water (or a water-based solution, like a dilute acid or dilute base)
-surrounding information - amount of solution (volume, mass), temperature change info about surroundings
Then use the second equation [nHx = -mcT]
-when working with the mcT portion of the equation, make sure that mass (m) and the heat capacity (c) and the temperature change (T) are all for the same substance (the surroundings)


If the surroundings are not mentioned
-use the first equation



Other tidbits to consider
-the question may ask for or provide mass - convert to moles (n)

From today:
Do the following questions. Use proper form with your solutions.

Page 308 # 2 and Page 312 #1ab & 4** [H = nHx or nHx = -mcT]*
Page 310 – 4 & 5 and Page 312- 2, 3, 5
*where the H = 'delta'H
**don't let p312 #4 confuse you, the temperature mentioned is meant to mislead you, did it?

Day 1 of Energy q=mct

- did a little bit of q = mc 'delta't
the mathematical calculations involve heat energy, but there is no acknowledge as to the origin of the energy - that will change - and soon
-terms, terms, terms.....
-system - the actual reaction
-surroundings - environment in which the reaction occured, typically water
-why water" (1) readily available (2) flows easily (3) high specific heat capacity - absorbs heat without experiencing a great temperature change (unlike some metals for example)
-when working with any dilute solution surroundings - assume that it has the same heat and density properties as pure water (c=4.18 J/gC, D = 1g/mL)

Energy Unit Ouline

• calculating enthalpy change q=mct
• molar enthalpy calculations – comparing system and surroundings
                o nHx = H and nHx=-mct [Could not get the 'delta' symbol]
• 4 ways to represent enthalpy changes
A few methods to determine the energy change associated with a chemical reaction
• Method 1: Hess’s Law – add up some equations then add up the enthalpy change of each equation
• Method 2: Standard Enthalpies of Formation – using tabulated data
• Method 3: Bond energies – using still more tabulated data, this time: [bonds broken – bonds formed]
• Entropy – will a reaction tend to be spontaneous?
• Measuring Rates of Reactions – graphically and given experimental data & a balanced chemical equation
• factors Affecting Rates of Reactions
• Rate Laws
• Potential Energy Diagrams
• Collision Theory
• Mechanisms

Test Preparation

Test Preparation this is my second attempt at posting this puppy
Test Outline:
-16 multiple choice questions - you will be able to write on the multiple choice question sheet, mark it up, put "X's" through those letter choices that are obviously incorrect, hopefully there is only one answer left at that point (maybe two - one correct, one not - pick the correct answer)
-a 'bunch' of written/drawing/sketching/complete the table questions
-please know the difference between Lewis, energy level diagram, 3-D sketch, orbital sketch
-Total ~ 62 marks (or something right around there....)


SCH4U - Atomic Structure Unit Outline Once again.... things to know

Atomic models (Dalton, Thomson, Rutherford, Chadwick & Bohr)
sketch of the model and a brief description of each model; know which contains e,p & n and where they are located in the model

Photoelectric effect - describe it; impact of colour of light & intensity of light

Spectral lines bright and dark line spectrum of hydrogen -leading to the Bohr model
connecting the both line spectra to the Bohr model
Spectral line splitting
further refinements of the Bohr model
in terms of orbitals, what does each type of spectral line splitting identify?
-high resolution spectroscopy revealed...? influence of a magnet suggested...?

Energy level diagrams - know how to make them ...
fill according to the order of filling (spdf blocks on the periodic table)
-Aufbau, Hund's Rule & Pauli Exclusion

Electron configurations (complete, kernel, special cases (Cr column & Cu column), ions)
use the periodic table of elements as an aid [see Nelson page 188 for two helpful diagrams]
should be able to write the actual electron configuration for any element [includes the two columns of exceptions]
from electron configuration (either complete or kernel) identify the appropriate electron changes to achieve an ion charge

Quantum Numbers {n, l, m, s}
-connection of each number to spectroscopy evidence
-significance of each letter (n represents, l represents....)
-be able to interpret a set of numbers as being correct (possible orbital?) or incorrect (what is wrong with the number set?)

Quantum Model
-those orbitals - s and p [px py pz]
-never did sketch those d's....

Lewis Structure [following the rules] - draw a Lewis structure for any molecule
if you are going to follow the rules, then you had better know the rules, right? [Nelson text page 229]

Atomic Modeling
-based upon the Lewis structure - be able to sketch the 3D shapes, identify the name & bond angle
i.e. 4 atoms attached to central, no lone pairs = tetrahedral; 3 atoms attached, 1 lone pair = trigonal pyramidal
basic attributes of the various shapes [Nelson text pages 243-245]

Hybridization (sp3, sp2 and sp) - connection to molecular shapes (if you know the shape you know the type of hybridization)
-sp3 = tetrahedral or trigonal pyramidal or angluar (has four orbitals)
-sp2 = trigonal planar (has 3 orbitals)
-sp = linear (has 2 orbitals)
-be able to make the three different types of orbital sketchs (sp3, sp2 and/or sp)
-on orbital sketch be able to identify:
sigma (overlap with a hybrid) and pi bonds (p-orbital overlapping with another p-orbital)

Liquid state bonding (London, dipole-dipole, hydrogen bonding)
-from 3-D structure - be able to identify a molecule as polar/nonpolar
-if nonpolar - only LD
-if polar - LD and DD (maybe also HB if there is a H-N, H-O and/or H-F)

Solid state bonding [ionic, metallic, molecular & covalent network]
-know the properties of each type of solid [summary Nelson text page 273]
-ionic - metal + nonmetal - hard, generally: high melting point + soluble in water
-metallic - a metal (Fe(s), Pb(s)) - conductors, electron sea model (free moving 'sea' of valence electrons)
-molecular - nonmetal + nonmetal - CO2, H2O - generally low melting point, nonconductors
-covalent network - memorize the few of them (SiO2, SiC, CD) - very hard, high melting point, generally nonconductors