Functional Groups - Ahmad Kilani

Functional Groups

Definition: a Functional group is a part of the organic molecule which is neither a C atom or an H atom.  There are many types of individual atoms or polyatomic ions that make a functional group, each having it's own properties.

For example, the functional group in this molecule would be Oxygen (Aldehyde).

There are many different types of functional groups, such as Aldehydes, Ketones, Halides and Nitro compounds, Esters, Ethers, Amines.  Each has a different functional group, and with it, different naming.


**We're only going to be looking at the first 3 functional groups (Aldehydes, Ketones, Halides And Nitro Compounds)

Halides and Nitro Compounds:

For the Halides, there are 4 elements that form this functional group;
-Fluorine (Fluoro)
-Bromine (Bromo)
-Chlorine (Chloro)
-Iodine (Iodo)

Nitro Compound (just one);
-NO2 (Nitro)

When naming a compound that contains a halide or nitro, use the name in the brackets.  For example;

  

To name this compound, we'd say 1-fluorohexane.  If there is more than one atom of the same element, use (di, tri, tetra etc.) prefixes.  Same naming rules apply for nitro.
**Don't forget that the names of the compounds are in alphabetical order (ie 1-bromo-2-fluorohexane)

Properties;
- Generally insoluble in water
- Compounds containing Fluorine are inert
- Compounds containing Bromine and Chlorine are more reactive, but still only react under extreme conditions
- Compounds with Iodine are very reactive
- Nitro compounds tend to be unreactive, yet explosive
- Nitro compounds generally have a nice smell

Aldehydes and Ketones:

Both Aldehydes and Ketones are organic molecules with double oxygen bond.  The difference between the two is that aldehydes have the double bond on either end of the compound.  Ketones on the other hands, can form double oxygen bonds with any carbon atom EXCEPT the ones at the ends.

Naming: For aldehydes, change the "e" in the alkane, alkene, alkyne, with "al"... So instead of propane, you would write propanal.  You never put a number before the compound's name if it's an alkane.  But you could write 2-propEnal (the 2 represents where the double bond is not where the O is)
- For Ketones, it's very similar, instead of changing the "e" at the end with "al", you change it to "one". So for example 3-propanone.  The number in front of the compound represents where the oxygen double bond takes place.

Properties;
- Aldehydes and ketones are easily oxidised
-  They're both liquids, the boiling point rises as the molecule gets bigger

Alcohols:

Alcohols are molecules with the functional group "OH".  Alcohols are basically an alkane with single or multiple OH functional groups.

One of the oldest types of man made alcohol is Ethanol

Naming: Like previous functional groups, you switch the "e" part of the molecule with "ol" this time.  With alcohol, more than one OH bond can take place, changing the name of the compound.  So you put a prefix for "ol" at the end of the name.  For example 1, 2, 4 - propanetriol.

Properties:
- Soluble in water
- The bigger the molecule the less soluble

Here's a quiz to test what you've learned today

Nick Kim-Alkene and Alkyne

This time we are going to find unsatrured hydrocarbon, means they are not single bond.

Alkene= double bonded
Alkyne=triple bonded

Naming is simialr to the alkane, you just need to put -ene instead of -ane. Same as alkyne -ene instead of -ane.

Ex,2-hexene

first you write down the number of carbon which is 6

c c c c c c

the 2 represent where double bond is

c-c=c-c-c-c

then put hydrogen

CH3-CH=CH-CH2-CH2-CH3

Notice where second carbon and third carbon only have one hydrogen.

Alkyne= Triple bond

This is very similar to the double bond

ex, 3-Hexyne

 Same as alkene, the number represent where the bond is, and it's triple, thus there is no hydrogen in third and fourth( between fourth and fifth sould be - sorry)

Here is the video that will help

Nick Kim- Organic Chemistry

Hydro Carbon- Molecule that only consist with hydrogen(H) and Carbon(C).
Since, Carbon has 4 valence electrons, it can bond to four sides.

Ex, Methane. Like you see Carbon goes middle because it is futher away from the full shell than hydrogen and Hydorgen bonds on four side.



This is called Alkane, it is satured hydrocarbon(single bond)

There are three ways to show Alkane 

what you see in example is full structure.

other one is called condensed structure. It looks like this.

ex, methane

CH3CH2CH3

and last one is called molecular formula

ex,methane

C3H8

 Number of carbon determine the name of alkane and also number of hydrogen.

Name you just need to memorize, but number of hydrogen is easy. You just need to multiple number of carbon and add 2. Ex) Methane CH4, 1x2=2 2+2=4 4 hydrogen

Note: not always hydrogen bonds to carbon, it can bon with other carbon

Alkyl group is an alkane which has one missing hydrogen,and it attaches to alkane group(branched hrdro carbon)

Ex,  CH3-Methyl=CH3 attached to propane.

When you named it is, 2-methly-Propane. the number only indicate which carbon it attached to, you can read from left to right or right to left.

Here are example





Chemical Bonding by Greg Sra

Bonding involves valence electrons only.
Atoms gain, lose, or share electrons until they have a stable octet.
There are 3 types of Bonding.
1) Ionic Bonds. An Ionic bond is formed when 2 electrons are transferred amongst each other.
2) Nonpolar Covalent bonds. A Nonpolar Covalent bond is formed when electrons are shared equally.
3) Polar Covalent Bonds. A Polar Covalent bond is formed when electrons are shared unequally.

Electrostatic Force
An electrostatic force exists between charged particles because of attraction or repulsion. Operates equally with each direction getting equal amounts of energy. Charged particles are put into crystal latices.
Basic Electrostatic Relationships:
1) Opposite charges attract each other.
2) Similar charges reject each other.
3) The longer the distance apart from 2 charged particles, the smaller the attracting force is between them.
4) The stronger the force of attraction is dependent on the charge of the particle.

Ionic Bonds
Metals usually lose valence electrons to non-metals, while non-metals gain the non-metals. This is an example of electrons being transferred. Once metals lose electrons they become positively charged ions or Cations. Once non-metals gain electrons they become negatively-charged ions or Anions. They are very strong with high melting points, its take massive amounts of energy to break them apart.

Electronegativity
The value of the tendency of an atom to take away  electrons from near by atoms.  Metals tend to have low electronegativity values in comparison Non-metals have higher values.  The scale that is applied to measure electronegativity is the Pauling Scale. This scales goes from Os & Fr which is 0.7 on the scale to 4.0 which is Fluorine.  Atoms with high values of Electronegativity will actively attract their own electrons and electrons from near by atoms. Ionization Energy also part takes in this.


Calculating Electronegativity Difference
The simple formula is below. In caps.
ENEGRY DIFFERENCE= {ENERGY 1 - ENERGY 2}


Non Polar Covalent Bonding
Covalent bonds like Ionic bonds are strong and need large amounts of energy to break them apart.Non polar covalent bonding has equal amounts  of energy spread apart. It is constructed when two atoms  don't have completed shells. They share one or more electron trying to satisfy the Octet rule. The electrons at the same time are attracted to the nucleus of each atom. Non-metals will not let go of their own electrons. Single molecules that contain intramolecular covalent bonds are attached together with intermolecular forces.

Polar Covalent Bonding 
Molecules that have electronegativity differences between .5-1.8 are thought to be covalent. But without equal sharing of electrons. This is called a Polar Covalent bond. An atom with a greater electronegativity will pull the electron toward its self and the electron will be closer to the atom with a higher electronegativity.

Super Chill Music

Kimistry got the slow beat goin.  Gonna make you warm and fuzzy while you read.

Electron Dot & Lewis Diagrams by Greg Sra

Electrons are represented by dots in electron dot diagrams. The nucleus is represented by the atomic symbol. There are 4 orbitals having at most 2 electrons per orbital. Each orbital is given an electron before it pairs up. The dots are put into 4 groups.With 8 electrons signifying a closed shell or noble gas.

Lewis Diagrams:

1) Firstly you must find out how many valence electrons are in your chosen elements. Adjust this number by subtracting an electron for each positive charge. Or by adding an electron for a each negative charge in the atom. Then count the electrons remaining.
** You want your atom to become stable, the only way to do this is by having 8 electrons in the outer shell.  (Hydrogen only needs 2 electrons)

2) Then select your central atom. A central atom is the atom that is the farthest away from a closed shell. (Metal Ion goes in center if available) H&F are an exception.Place the electrons so they fill each orbital.

3) Use the remaining valence electrons to fill out the orbitals. Place remaining electrons on the central atom.

4) Make multiple bonds if the central atom is not an octet.

 Covalent Compounds
Two atoms share a pair of electrons to create a full outer shell. This pair is called the Bonding Pair.

Lone pairs or non-bonding pairs are the pair of electrons which do not join together. Single bonds can be represented by 2 dots or a single line.

HISTROY OF THE PERIODIC TABLE

IN THE BEGINNINGGGG

-people believed everything was made up of fire, earth, wind, and water.

However, a russian chemist Dimitri Mendeleev would be the first person to write a periodic table.  He grouped different elements based on their properties.






PICS

Periodic Table Trends

Periodic Trends
 Metallic Properties: The properties of the elements change fro metallic to non-metallic going left to right across the periodic table.
The elements become more metallic going down a family in the periodic table.

Atomic Radius
Atomic radii of an atom increases going across a row left to right, it also increases going down a group.
Going left to right across a given period the atomic number (and number of protons) increases, and the positive charge on the nucleus increases.

Ionization Energy: is the energy need to completely remove an electron from an atom. Ionization energy increases going up and to the right. All noble gases have high ionized energy.   Helium has the highest ionization energy while Francium has the lowest.

 Electronegativity:  Is the tendency of an atom to attract electrons from a neighboring atom. Electronegativity energy increases going across a row left to right. It decreases going down a group.

Reactivity: When a metal moves down a row and right it becomes more reactive. Non-metals are the opposite as once they go up a row they become more reactive.

 Melting & Boiling Point: Elements from the centre have a higher boiling point and Noble Gases have

the lowest melting point.

blog workers on strike

blog posts wont be updated until the day before ms chen marks them.  Then someone will step up to the plate and write the last 10000 blogs we missed.

Periodic Table - History

A necessary step to the construction of the periodic table was the discovery of the individual elements. All of elements including copper, lead, silver, gold, and mercury have been known for a while, Henning Brand's discovery of phosphporous was the first scientific discovery.

As 200 years passed by, chemists started regarding the properties of the elements. By 1869, 63 elements had been discovered. 

As the number of known elements grew, scientists began to recognize patterns in properties and began to develop classification schemes.

Law of Triads

In 1817 Johann Dobereiner noticed that the atomic weight of strontium fell midway between the weights of calcium and barium, elements possessing similar chemical properties.

After the discovery of the halogen triad (chlorine, bromine, and iodine); and the dicovery of the alkali metal triad (lithium, potassium, and sodium); he proposed that the nature of the triads allowed the middle element to be the average of the two elements (atomic mass). This si known as the Law of Triads.

 

 

First Attempts At Designing the Periodic Table

The periodic table demonstrates the order of chemical elements based on their chemical and physical properties. The credit to the first "draft" of the periodic table has to be given to Beguyer de Chancourtois that positioned a cylinder based on increasing atomic weight which then led to the conclusion that the properties of elements are the properties of numbers and they should be organised based on that.

Law of Octaves

In 1863, John Newland classified 56 elements into 11 groups based on their properties; physical and chemical. He said that after every 8 elements, the properties re-appear. He then propsed his version of the periodic table and the Law of Octaves. This law stated that any given element will exhibit analogous behavior to the eighth element following it in the table.

 

Demetri Mendeleev 

Russian chemist that arranged te periodic table based on the atomic mass of elements; and he put the elements with similar characteristics and properties under eaach other. He left some gaps for elements that are yet to be dicoverred and he did note that they will be discoverred to fit in the gaps that share the same properties. Examples of elements include gallium, scandium and germanium.

Mendleev's periodic table was important because it possessed the means of "periodic law" which states the elements vary periodically with their atomic weight.

 

Discovery of the Noble Gases

Argon was discoverred in 1895 by Lord Rayleigh. He noted that this element did not fit any of the groups previously organized by Mendeleev and Newlands. 3 years after that, Ramsey suggested it should be put in the group between chlorine and potassium in one family with helium. The referred to it as the "zero group" because they had no valence electrons. Ramsey then predicted the discovery of the properties of the element neon.

 

The Modern Periodic Table

After the disovery of plutonium by in 1940 by Seaborg, and the discovery of elements from 94 to 102, he made some changes during the 20th century. He also placed the actinide series below the lanthinide series in 1951. He was awarded the Nobel Prize in chemistry and an element was named after him (seaborgium).

 

Periodic Table - Families

Scientists group families of elements by their chemical properties.  Each family reacts a different way with the outside world.  Metals behave differently than gases and there are even different types of metals.  Some don't react, others are very reactive, and some are metallic.

Usually, the colums of the periodic table are used to define families.  The inert gases are all located in the far right column of the table.

Families

- Alkali Metals

They are found in group 1 of the periodic table:

• Highly reactive metals that do not occur freely in nature.
• These metals have only one electron in their outer shell.  Therefore, they are ready to lose that one electron in ionic bonding with other elements.
• Malleable, ductile, good conductors of heat and electricity.
• Softer than most other metals.

Sodium

- Alkaline Earth Metals

They are found in group 2 of the periodic table:

• Same properties as alkali metals but an ionization number of +2, making them very reactive, but less reactive than the alkali metals.

Magnesium

- Transition Metals

• Transition elements are ductile and malleable, they conduct electricity and heat.
• Their valence electrons are present in more than one shell.  This is why they often exhibit several common oxidation states

Gold

- Halogen Gases

• Non-metallic elements are found in group 17 of the periodic table.
• All halogens have 7 electrons in their outer shells, giving them an ionization number of -1.

Bromine

- Noble Gases

• Group 18 of the periodic table.
• Ionization number of 0.  This prevents them from forming compounds readily.
• All noble gases have 8 electrons in their outer shells, making them stable.

- Lanthanide and Actinide series

• All of them are found in group 3 of the periodic table, 6th and 7th periods.
• most of them are man-made (synthetic)
• Same properties as other metals

Electronic Structure

 Electronic Structure(configuration) is the arrangement of electrons in energy level  around an atomic nucleus. It tells us how many electrons are in each orbital.
 For example, Electronic structure for Na(sodium) is 1s2 2s2 2p6 3s1.
It looks complicated right? But as long as you get the rules, it will be really easy.

First there are four types of shell. There are s,p,d,and f. Like u can see from the periodic table below those shells are based on periodic table.

  To write electronic configuration, you just needed to find location of the element that you want, and write down orderly from left to right.
 Let's use Na for the example, Na has 11 electrons,and it's at 3rd period fist group. Fisrt we start with left top. there are two elements are in 1s(1 simply represent the  period). Thus, you write 1s2, and there are nothing on the 1period on the right side, so we go to period 2. They have two elements as well, thus you write 2s2, then there are 6 elements in 2p, thus you write 2p6, got it? So,over all we have 1s2 2s2 2p6 and finally where Na is 3s1. Thus,  answer is 1s2 2s2 2p6 3s1.
Just be aware of d d start wih row 3 instead of  4









Core Notation
 Some Scentists are really lazy thus, they found the easiler way to write elecronic configuration. It's easy you just need to find the near noble gas and start the electronic configuration from there. Thus, for Na, Ar is the closest noble gas, thus u write (Ar)3s1.

Valence Electrons
They are electrons that are located most outer shell, if we have core notation we just simply need to count the numbers of elecrons exept d and f. For example,Na has 1 valence eletrons
 Here is the video that will help

                                         

Atomic Structure

Atoms are composed of three type of particles: protons, neutrons, and electrons.

Protons and neutrons are responsible for most of the atomic mass.
The mass of an electron is very small (9.108 X 10^-28 grams).

1 - Now let's start with Neutral Atoms:

Both the protons and neutrons reside in the nucleus. Protons have a postive (+) charge, neutrons have no charge, ie they are neutral. Electrons reside in orbitals around the nucleus. They have a negative charge (-).

The number of protons determines the atomic number, e.g., H = 1. The number of protons in an element is constant (e.g., H=1, Ur=92) but the neutron number may vary, so the mass number (protons + neutrons) may vary.

Helium Atom

 2 - Ions:

- In an ion, number of electrons =/ number of protons, but protons = atomic number.
- Electrons are either lost or gained, making the ion either positive or negative.






3 - Isotopes:

The same element may contain varying numbers of neutrons; these forms of an element are called isotopes. The chemical properties of isotopes are the same, although the physical properties of some isotopes may be different. Some isotopes are radioactive-meaning they "radiate" energy as they decay to a more stable form, perhaps another element half-life: time required for half of the atoms of an element to decay into stable form. Another example is oxygen, with atomic number of 8 can have 8, 9, or 10 neutrons. 

To sum this up:

- Isotopes are atoms with same number of electrons and protons, but different numbers of neutrons.
- Different numbers of neutrons means different atomic masses.
- Different amounts of isotopes exist for different elements.








The mass number of elements can be calculated by getting the averages of the atomic masses of isotopes. For example:

potassium has three main isotopes; potassium-39 (93.26%), potassium-40 (0.0117%), potassium-41 (6.73%), so to get the average you multiply the percentages by their atomic masses, then add them together.

(39*0.9326) + (40*0.000117) + (41*0.0673) = 39.13538g/mol

*Always; # neutrons = mass # - atomic #, electron's mass = 1, neutron mass = 1837, proton mass = 1836

April 14

History of Chemistry

The theories of Aristotle, which lasted two thousand years, were that matter was made of atomos, the smallest pieces of matter.  Everything was made of a combo of earth, air, fire, and water.

In the late 1700s, Lavoisier introduced the first version of the Law of Conservation of Mass and the Law of Definite Proportions

In 1799, Proust stated that if a compound was broken down into its constituents, the products would exist in the same ratio as in the compound

Dalton (1800s) discovered that atoms were solid, indestructable spheres. His 5 main points of the Atomic Theory were:

-Elements are of tiny particles called atoms

-Atoms of a given element are identical 

-Atoms of different elements are different by weights
-Atoms from different elements combine to form chemical compounds

-Atoms cant be destroyed, created, or divided.

JJ Thomson

- Thomson introduced the Raisin Bun diagram.  ( solid positive spheres with negative particles embedded in them)

April 6th- Percent Purity

Percent Purity is the percent of a specified compound or element in an impure sample.

Example:

Chalk is almost pure calcium carbonate. We can work out its purity by measuring how much carbon dioxide is given off. 10 g of chalk was reacted with an excess of dilute hydrochloric acid. 2.128 liters of carbon dioxide gas was collected at standard temperature and pressure (STP).
The equation for the reaction is
CaCO₃ (s) + 2HCl (aq) → CaCl₂ (aq) + H₂O (l) + CO₂ (g)

 

Solution:

Step 1: Calculate the grams from the volume

1 mole of CaCO₃ gives 1 mole of CO₂
1 mole of gas has a volume of 22.4 liters at STP.
22.4 liters of gas of gas is produced by 100 g of calcium carbonate
and 2.128 liters is produced by 2.128 ÷ 22.4 × 100 = 9.5 g

Step 2: Calculate the percent purity

There is 9.5 g of calcium carbonate in the 10 g of chalk.
Percent purity = 9.5 ÷ 10 × 100% = 95%

April 4th - Percent Yield

Percent Yield

• The percentage yield is the ratio between the actual yield and the theoretical yield multiplied by 100%.  It indicates the percent of theoretical yield that was obtained from the final product in an experiment. 

• The percentage yield can be calculated using the mass of the actual product obtained and the theoretical mass of the product calculated using the balanced equation of the reaction.

Percentage Yield =     Mass of Actual Yield       x   100%

                  Mass of Theoretical Yield

Theoretical Yield

• this is how much product will be synthesized in ideal conditions.

• To determine theoretical yield, multiply the amount of moles of the limiting reagent by the ratio of the limiting reagent and the synthesized product and by the molecular weight of the product.

 Actual Yield

• this is how much product was actually synthesized in the experiment.
  
• Example:  0.135 g acetylsalicylic acid 

Practice Problem

In the following reaction, 0.157g of p-acetaminophenol was used to react with 0.486 g of acetic anhydride to produce acetaminophen and acetic acid.  The product was purified and acetimophen was extracted.  The actual mass of acetaminophen produced was 0.198 g.  Determine the theoretical yield and the percent yield of isopentyl acetate. p-Aminophenol     +     Acetic anhydride     à     Acetaminophen      +    Acetic acid     C6H7NO                                 C4H6O3                    C8H9NO2                  CH3COOH Solution   molar mass of p-aminophenol =109.1g/mol molar mass of acetic anhydride = 102.1 g/mol moles of p-aminophenol = mass/molar mass                                   = 0.157g/(109.1g/mol)                                   = 0.00144 mol moles of acetic anhydride = mass/molar mass                                          = 0.486g/(102.1g/mol)                                          = 0.00476 mol Theoretical Yield = moles of acetamiophen x molar mass of acetaminophen                          = 0.00144 mol x 151.2g/mol                          = 0.217 g Percent Yield =         Actual Yield        x 100%                             Theoretical Yield                     =            0.198g      x 100 %                                   0.217g                     =  91.2 %

March 12th- Excess & Limiting Reagents

Today we learned about  EXCESS & LIMITING reactants.

Chemical reaction equations give the ideal stoichiometric relationship among reactants and products.
However, the reactants for a reaction in an experiment are not necessarily a stoichiometric mixture. In a chemical reaction, reactants that are not use up when the reaction is finished are called excess reagents. The reagent that is completely used up or reacted is called the limiting reagent, because its quantity limit the amount of products formed.

Example 1 

using the following equation, find the excess reagent when 10.0 g manganese metal is allowed to react with 10.0g nitric acid

first make the formula

3Mn + 8HNO3----- 3Mn(NO3)2 + 2NO + 3H2O

then you find the mass of HNO3 using 10g of manganese(order doesnt matter)

10g x 1moleMn/54.9 x 8moleNO3/3moleMn x 63gHNO3/mol HNO3
=30.6g of HNO3 .......since you only need 10g of HNO3, but you have 30.6g of HNO3 it is excess
it also means  Mn is limiting

Example 2 

Find the limiting reagent and the reactant in excess when 0.5 moles of Zn react completely with 0.4 moles of HCl

1. Write the balanced chemical equation for the chemical reaction     Zn + 2HCl -----> ZnCl₂ + H₂
    
2. Calculate the available moles of each reactant in the chemical reaction

   moles of Zn = 0.5

   moles of HCl = 0.4

3. Use the balanced chemical equation to determine the mole ratio of the reactants in the chemical reaction

   Zn : HCl	Or	HCl : Zn
   1 : 2		1 : ½

4.  Compare the available moles of each reactant to the moles required for complete reaction using the mole ratio     If all of the 0.5 moles of Zn were to be used in the reaction it would require
       2 x 0.5 = 1.0 moles of HCl for the reaction to go to completion.
       There are only 0.4 moles of HCl available which is less than the required 1.0 moles.
       If all of the 0.4 moles of HCl were to be used in the reaction it would require
       ½ x 0.4 = 0.2 moles Zn.
       There are 0.5 moles of Zn available which is more than the required 0.2 moles
    .
5. The limiting reagent is the reactant that will be completely used up during the chemical reaction.
       There will be some moles of the reactant in excess left over after the reaction has gone to completion.     The limiting reagent is HCl,
       all of the 0.4 moles of HCl will be used up when this reaction goes to completion.
       The reactant in excess is Zn,
       when the reaction has gone to completion there will be
       0.5 - 0.2 = 0.3 moles of Zn left over.
   
   

Here are more practice questions!

http://www.ausetute.com.au/exceslim.html

here is the website that will help you
http://www.youtube.com/watch?v=Vaiz0zLesHk&feature=related

March 7- Stoichiometry Calculation

Today we did stoichiometry calculations involving Molarity and STP.

Molarity is easily defined by this one equation. Molarity=  Moles
                                                                                   Litres

STP is 22.4 litres/mole

Example

1. How many moles of nitrogen gas is needed to react with 44.8 liters of hydrogen gas to produce ammonia gas?

3H₂   +   N₂    2NH₃
GIVEN: 44.8 L of H₂ at STP.
FIND: mols of N₂.
Here the sequence is: GIVEN liters of H₂ at STP, CHANGE liters of H₂ at STP to mols of H₂, MOL RATIO to change from H₂ to N₂. There is no need to go any further to change the N₂ into mols, because the mol ratio leaves the material in that unit anyway.






How many liters of ammonia are produced when 89.6 liters of hydrogen are used in the above reaction?
The "above reaction" from problem #1 is: N₂   +   3H₂    2NH₃

GIVEN: 89.6 L of H₂ at STP.
FIND: Volume of ammonia (in liters at STP)
Take the GIVEN quantity, use the Molar Volume of Gas at STP (MVG) to change it to mols, change the material with the mol ratio (MR), and change the mols of new material to the requested liters at STP using the MVG again.

March 5th - Nick kim

 Today we have learned how to do Stoichiometry calculation involving particles-moles-mass
we have acutually covered how to do conversion between particles-moles-mass, thus we just need to know how are we gonna use stoichiometry to find answers.
 [Ex] Cu+2AgNO3----Cu(NO3)2+2Ag

How many grams of AgNO3 are required to completely react with 2.1 moles of Cu

First we should find moles of AgNO3 in order to find its weight. Thus, we use what we learned last class Stoichiometry( using ratio to find the number of moles)

2.1moles of Cu x 2moles of AgNO3/1mole of Cu-------- If you look above then you see ratio between Cu and AgNO3 is 1:2 right so you put that into fraction and make unwanted element cancel each other.

Therefore we end of having 4.2 moles of AgNO3-------- and now we need to convert this into grams, u find the mass of AgNO3 from periodic table which is 107.9g+14g+16(3)g=169.9g
Then we do mole conversion.

4.2 moles of AgNO3 x 169.9g of AgNO3/ 1 mole of AgNO3------ moles cancel each other and left with multipication.

=713.58(careful about the sigfig)

Here is the diagram that will help.

More practices

http://www.standnes.no/chemix/examples/stoichiometry-problems-chemistry.htm

video that will help us to understand more

http://www.youtube.com/watch?v=49k88Alfh88

march 1 marcus lu

stoichiometry!

Stochio is Greek for element, and metry means measurement.  Therefore, stoichiometry is the branch of chemistry that deals with quantities of elements and compounds involved in a reaction.


Using the example 4NH3 + 5O2 --> 6H20 + 4NO, we can conclude that the mole ratio is 4:5:6:4.

4 moles of NH3 react with 5 moles of O2 to produce 6 moles of H20 and 4 moles of NO.

AN example question is : How many moles of O2 will be formed when 9000 moles of H20 is decomposed?

9000mole H20 X 1mole O2 / 2mole H20 = 4500 mol O2

**** we divide the 9000moles of H20 by 1/2 because in H20, there is 2 moles of H and 1 mole of O!

February 21st -- Ahmad Kilani

Enthalpy Calculations

Key Concepts

• The heat content of a chemical system is called the enthalpy (symbol: H)
• The enthalpy change (H) is the amount of heat released or absorbed when a chemical reaction occurs at constant pressure.
• H = H_(products) - H_(reactants)
• H is specified per mole of substance as in the balanced chemical equation for the reaction

The enthalpy change, or H,  for each reaction is unique. So what relationship exists between the heat produced or absorbed by a reaction and the amount of reacting substance?

The energy change in these reactions varies directly as the number of moles of substance reacted or formed. The factor that determines the amount of heat absorbed or released is the H of the reaction: 

Moles of compound reacted or formed	Varies directly with	Heat absorbed or released in the reaction
	<--------------------->
	H reaction (kJ)

The energy is a variable because it differs from one reaction to another. However, it is a given that it is going to be positive when it is absorbed (i.e LHS, or reactants side); and negative when it is produced (i.e RHS, or products side). 

Examine the following reaction:

2 C₄H₁₀ (l) + 13 O₂ (g) ---> 8 CO₂ (g) + 10 H₂O (g) + 5315 kJ

The equation tells us that 8 moles of CO2 (g) releases 5317 kJ , since the relationship is a direct one then 2 moles would release one quarter as much heat or 2 moles would release 1,329 kJ.

To calculate heat changes using equations, we will perform the following steps

1) calculate the number of moles of substance reacted or formed.
2) create a proportion using the balances and heat in the chemical equation.
3) solve for missing quantity.

Question:

Calculate the amount of heat released when 25.0 grams of C₄H₁₀ (l) is burned in oxygen using the equation above.

Solution:

.

Calculate the number of moles of C₄H₁₀ (l), and times it by the energy per one mole.

MM of  C₄ is  12x4= 48.0 g/mol

MM of   H₁₀  is  1x10=10.0 g/mol

Total MM is 58.0 g/mol

Therefore, 

the conversion is from grams to moles to energy (heat).

25.0 g  x  1 mole   x  2657.5  KJ     =  1145.47 KJ   ---> ( 3 sig figs) = 1150 KJ 

                 58.0 g           1 mole

So 1150 KJ  of heat would be released when 25 grams is burned.