advanced chemistry lessons

Emphasizing Endosulfan and Organic Substance: What is the Ecological Danger of the MV Princess Tragedy?

2009-03-14T19:54:00.000-07:00

The MV Princess of the Stars was a ferry owned by Filipino shipping company Sulpicio Lines that capsized off the coast of San Fernando, Romblon at the height of Typhoon Frank last June 21, 2008. According to the Coast Guard, the ferry's manifest recorded 702 passengers including 50 children as well as 100 crew. The civil defense office said that the ship carried 626 passengers and 121 crew members. It was reported that a 10 metric tons of endosulfan, a restricted pesticide for use in pineapple plantations, was found in the sunken MV Princess of the Stars.

Endosulfan is a chlorinated hydrocarbon insecticide and acaricide of the cyclodiene subgroup which acts as a poison to a wide variety of insects and mites on contact. Endosulfan is a poisonous and highly toxic pesticide. It only needs a very small amount which is equivalent to only 8 milligram to kill someone who is affected with it. Our central nervous system will be the most damaged area in human body. These chemicals should not be taken with fruits and vegetable and passengers as well. Endosulfan brings many ecological danger which can probably lead to death.

Endosulfan breaks down into endosulfan sulfate and endosulfan diol, both of which, according to the EPA, have "structures similar to the parent compound and are also of toxicological concern…The estimated half-lives for the combined toxic residues range from roughly 9 months to 6 years." The EPA concluded that, "based on environmental fate laboratory studies, terrestrial field dissipation studies, available models, monitoring studies, and published literature, it can be concluded that endosulfan is a very persistent chemical which may stay in the environment for lengthy periods of time, particularly in acid media." The EPA also concluded that "endosulfan has relatively high potential to bioaccumulate in fish." It is also toxic to amphibians: low levels have been found to kill tadpoles. Several fish species are quite susceptible to endosulfan. Endosulfan is also quite toxic to birds and to shellfish. Birds in general are fairly sensitive to endosulfan poisoning. The symptoms persisted for up to a month in a few animals. It is moderately toxic to bees and is relatively non-toxic to beneficial insects such as parasitic wasps, lady bird beetles and some mites.

The Department of Health of the Philippines has temporarily banned the consumption of fish caught in the area. Endosulfan is classified as a "Severe Marine Pollutant" by the International Maritime Dangerous Goods Code.

sources:

MV Princess of the stars. Retrieved February 26, 2009, from Wikipedia: http://en.wikipedia.org/wiki/MV_Princess_of_the_Stars

NDCC update. Retrieved June 29, 2008, from NDCC web: http://210.185.184.53/ndccWeb/images/ndccWeb/ndcc_update/MV_princess_star/sitrep%207%20mv%20princess%20of%20the%20stars.pdf

Pesticide Information Profiles. Revised June, 1996, from Extoxnet: http://extoxnet.orst.edu/pips/endosulf.htm

http://hugsmiles.com/ladyinpurple/2008/06/28/enduslfan-a-poisonous-chemical-found-to-be-in-sunken-mv-princess-of-the-stars/

http://pmep.cce.cornell.edu/profiles/extoxnet/dienochlor-glyphosate/endosulfan-ext.html

Endosulfan health effects. Retrieved March 11, 2009, from Wikipedia: http://en.wikipedia.org/wiki/Endosulfan#Health_effects

electrolytic cells

2009-03-07T18:12:00.000-08:00

Electrolytic Cells

conversion of electrical energy back to chemical energy
decomposes chemical compounds by means of electrical energy, in a process called electrolysis; the Greek word lysis means to break up. The result is that the chemical energy is increased. Important examples of electrolysis are the decomposition of water into hydrogen and hydroxide, and bauxite into aluminium and other chemicals.(http://en.wikipedia.org/wiki/Electrolytic_cell)

E^o_cell = E^o_reduction(cathode reaction) - E^o_reduction(anode reaction)

If E^o_cell> 0, we have a spontaneous process (galvanic cell)
If E^o_cell<>

THREE COMPONENTS OF ELECTROLYTIC CELLS:

electrolyte (any substance containing free ions that behaves as an electrically conductive medium)
2 electrodes: anode and cathode

Galvanic cells compared to electrolytic cells

In contrast, a battery or galvanic cell, converts chemical energy into electrical energy, by using spontaneous chemical reactions that take place at the electrodes. Each galvanic cell has its own characteristic voltage (defined as the energy release per electron transfer from one electrode to the other). A simple galvanic cell will consist only of an electrolyte and two different electrodes. (Galvanic cells can also be made by connecting two half-cells, each with its own electrode and electrolyte, by an ion-transporting "bridge", usually a salt bridge; these cells are more complex.) The electrodes typically are two metals, which naturally have different reaction potentials relative to the electrolyte. This causes ions of one of the electrodes to preferentially enter the solution at one electrode, and another ion to leave the solution at the other electrode. This generates an electric current across the electrolyte, which will drive electric current through a wire that makes an exterior connection to each of the electrodes. A galvanic cell uses electrodes of different metals, whereas an electrolytic cell may use the same metal for cathode and anode.

A rechargeable battery, such as a AA NiMH cell or a single cell of a lead-acid battery, acts as a galvanic cell when discharging (converting chemical energy to electrical energy), and an electrolytic cell when being charged (converting electrical energy to chemical energy).(http://en.wikipedia.org/wiki/Electrolytic_cell)

for more information: http://en.wikipedia.org/wiki/Electrolytic_cell

electrochemical cells(o2-o4-o9)

2009-03-07T08:04:00.000-08:00

ELECTROCHEMICAL CELLS

conversion of chemical energy to electrical energy

an apparatus in which a spontaneous reduction oxidation reaction occurs

Parts of a Galvanic Cell

A Galvanic cell is usually separated into two compartments. The reducing and oxidizing species are not in direct contact. Instead an electrical wire is used to facilitate the transfer of electrons and a salt bridge is used to facilitate the transfer of ions.

cathode - the compartment in which reduction occurs. In the example shown above, the cathode compartment is composed of an aqueous solution of Cu(NO₃)₂ and a copper electrode (an electrode is the material that is exposed to the solution and, at the same time, is connected to an external wire). The reaction at the cathode (a reduction) for this case is:

Cu²⁺ (aq) + 2e^- ---> Cu (s)

anode - the compartment in which oxidation occurs. In the example shown above, the anode compartment is composed of an aqueous solution of Zn(NO₃)₂ and a zinc electrode. The reaction at the anode (an oxidation) for the above case is:

Zn (s) ---> Zn²⁺ (aq) + 2e^-

In a galvanic cell, electrons are flowing from the anode into the cathode. To complete the electrical circuit, a salt bridge is necessary. Inside the salt bridge, negative ions (anions) move toward the anode (where the positively charged Zn²⁺ is being formed) while positive ions (cations) move toward the cathode (where the amount of positively charged Cu²⁺

half-cell reactions

oxidation and reduction at electrodes

cell voltage

electromotive force (E) or cell potential

for more information about electrochemical cells: http://bouman.chem.georgetown.edu/S02/lect25/lect25.htm

electrochemistry?(o2-o3-o9)

2009-03-07T06:14:00.000-08:00

According to wikipedia.org, electrochemistry is a branch of chemistry that studies chemical reactions which take place in a solutions at the interface of an electron conductor (a metal or a semiconductor) and an ionic conductor (the electrolyte), and which involve electron transfer between the electrode and the electrolyte or species in solution. In short, electrochemistry is the branch of chemistry that deals with the relationship between electricity (flow of electrons) and chemical reactions (http://bouman.chem.georgetown.edu/S02/lect25/lect25.htm).

If a chemical reaction is driven by an external applied voltage, as in electrolysis, or if a voltage is created by a chemical reaction as in a battery, it is an electrochemical reaction. Chemical reactions where electrons are transferred between molecules are called oxidation/reduction (redox) reactions. In general, electrochemistry deals with situations where oxidation and reduction reactions are separated in space or time, connected by an external electric circuit to understand each process(wikipedia.org).

Oxidation is defined as the interaction between oxygen molecules and all the different substances they may contact, from metal to living tissue. Technically, however, with the discovery of electrons, oxidation came to be more precisely defined as the loss of at least one electron when two or more substances interact. Those substances may or may not include oxygen. While, reduction is the gain of electrons or the addition of at least one electron when substances come into contact with each other. (http://www.wisegeek.com/what-is-oxidation.htm)

RULES:

The oxidation # of free element is 0.
The oxidation # of ions = charge.
the oxidation # of -2 except peroxide (O2)(-1)
the oxidation # of H ion is always +1 except metallic hydride (-1)
the sum of the charges in a compound = 0
the algebraic sum of oxidation # of poly ions = charges

Identifying oxidizing and reducing agents in redox reactions

1. Assign oxidation numbers (follow the rules above).

2. After you have assigned oxidation numbers, identify the elements whose oxidation numbers have changed.

3. The reactions that we will study for this topic this semester are already balanced. Sometimes, reactions will be given as half reactions, for this particular instance, what is necessary is to balance the number of electrons before combining the two half reactions.

2008-10-04T05:24:00.000-07:00

Equilibrium

2008-10-02T14:35:00.002-07:00

Equilibrium came from the words "equus"(equal); and "libra" (balance).
Well, as what I have learned in this new lesson, A + B -> C is a forward reaction and if you reversed them the reversed reaction would be: C <- A + B. In the equation of equilibrium constant ( Keq = (C) / (A)(B) ): if Keq > 1 the concentration of the product is greater than the reaction of the reactant;
if Keq < 1 the concentration of the product is less than the reaction of the reactant; and
if Keq = 1 the concentration of the product and the concentration of the reactant are equal.

the graph are:

Thermodynamics(09-01-08->present)

2008-09-15T03:00:00.000-07:00

Thermodynamics, which came from the Greek word "therme" meaning heat and "dynamis" meaning power, is a branch of physics and is used extensively in chemistry and biochemistry.It studies the effects of changes in temperature, pressure, and volume on physical systems at the microscopic scale by analysing the collective motion of their particles using statistics. Roughly, heat means "energy in transit" and dynamics relates to "movement"; thus, in essence thermodynamics studies the movement of energy and how energy instills movement. Historically, thermodynamics developed out of need to increase the efficiency of early steam engines.(http://en.wikipedia.org/wiki/Thermodynamics#The_laws_of_thermodynamics)

Thermodynamics has 3 Laws:

1. The first law states that the energy of the universe is constant. It can only be transformed from one form to another.(conservation of energy)

equation:

∆E = heat(q) + work(w)

where work = -P∆V and the -P is the opposing pressure

so the equation for this law is:

∆E = q - P∆V

2. The 2nd law states the ∆S (change in entropy) of the universe must always increase.(entropy)

to predict whether a reaction is spontaneous or not. There are things that we should follow:

whenever the ∆G(Gibbs Free Energy) is negative, the reaction is spontaneous;

the reaction is spontaneous at all times if ∆H and ∆G are both negative and only ∆S is positive;

the reaction is spontaneous when the temperature is high and when ∆S and ∆H is positive;

the reaction is spontaneous when the temperature is low and when ∆H, ∆S, ∆G is negative; and

the reaction is nonspontaneous if only the ∆S is negative.

3. The 3rd law states that the entropy of a crystalline substance is zero at the absolute zero temperatue. (absolute zero temperature)

just add water.,september

2008-09-08T04:23:00.000-07:00

the next activity is about the changes in thermal energy. first we will define thermal energy. thermal energy is heat energy in transfer. heat is a form of energy. when heat it is in the process of being transferred, it is called thermal energy.

the objective of this activity is to know what will happen if you add cold water to the hot water when both have the same mass.

materials:

4 plastic foam cup

scissors

balance

thermometer

hot and cold water

procedure:

label the first cup with H for hot water and the second cup with C for cold water.

get the 2 cups then cut 2 to 3 cm from the top of each cup. using a pencil, poke a hole on the bottom of each cup, make sure that the thermometer will fit on both cover. label both cup with C and H.

measure the mass of cup without the cover. record.

add hot water (1/3 of the cup) to the cup labeled H and cold water (same amount) to the cup labeled C.

measure their mass then their temperature. record.

pour the cold water to the hot water. measure the temperature. record.

conclusion:

if you add cold water to the hot water with the same mass, the temperature will change because the heat coming from the water is absorbed by the cup then as you add cold water in it, the absorbed heat is transferred again to the water. the amount of heat transferred is equal to the amount of heat absorbed by the cup.

Thermal Energy is the kind of energy that is related to and/or caused by heat. When thermal energy is applied to a substance, the average velocity of the particles or molecules which make up the substance increases -- and it gets warmer!

thermochemistry(08-23-08)

2008-09-02T04:14:00.000-07:00

you know what thermochemistry means? thermochemistry is a branch of chemistry that deals with the relationship between chemical action and heat or the quantitative study and measurement of heat and enthalpy changes. thermochemistry, generally, is concerned with the heat exchange accompanying transformations, such as mixing, phase transitions, chemical reactions, etc., which includes calculations of such quantities as the heat capacity, heat of combustion, heat of formation, etc.
thermochemical equation shows the relationship energy changes and mass relationship.
example:
H2(g) + 1/2 O2(g) --> H2O(l); ∆H = -285.8 kJ (exothermic-heat is released)
HgO(s) --> Hg(l) + 1/2 O2(g); ∆H = +90.7 kJ (endothermic-heat is absorbed)

there are guidelines that are to be remembered in writing this equations:

always specify the physical states of all reactants and products

example:

liquid H2O to solid H2O the ∆H is +6.01 kJ/mol

solid H2O to liquid H2O the ∆H is -6.01 kJ/mol

when both sides of thermochemical equation is multiplied by a factor ,n, then ∆H must also change by the same factor

example:

2H2O -> 2H2O ∆H=2(6.01 kJ/mol)=12.02 kJ/mol

when we reverse the equation, we change the role of products and reactants. as a consequence, the sign changes but the magnitude of ∆H for the equation remains the same

example:

liquid H2O to solid H2O the ∆H is +6.01 kJ/mol
solid H2O to liquid H2O the ∆H is -6.01 kJ/mol

solving for thermochemical equations:

problem:

Calculate the heat evolve when 74.6 g of SO2 is converted to SO3.

SO2(g) + 1/2 O2(g) -> SO3(g) ∆H = -99.1 kJ/mol

get the number of moles of SO2:

74.6g SO2x 1 mol of SO2 / 64.07g SO2 = 1.16 mol SO2

*64.07 g of SO2 is the molar mass of SO2 which is to be computed first if it is not given. to compute the molar mass, get the mass of S and 2O. after you get their mass, combine them by adding the mass of S and 2O.

multiply the answer to the ∆H which is -99.1 kJ/mol:

= (1.16 mol SO2)(-99.1 kJ/mol) ->cancel the mol

heat evolve = -115 kJ

rust cleaning

2008-08-29T22:10:00.000-07:00

last august 26, we had our rust cleaning in front of our room. it's because of the experiment we made last week. and the salt is scattered all over the stair's metals that made them rust. the salt has its own contents which made the metal exposed to air. so before it damages the metal, we need to repaint the metal so that the whole will be covered and it will not anymore be exposed to air.

thermal energy of ice cream(august 20)

2008-08-21T04:10:00.000-07:00

maTeriALs:

2 cups evaporated milk
4 tablespoons of brown sugar
chocolate powder (any flavor of your choice)
container
1 kilo of rock salt
crashed ice (7 pcs-depends on the size of the container)
can/

sTePs:

mix the ingredients (evaporated milk, brown sugar, chocolate powder) in the can/;
prepare the container, then put the ice and cover the outer part of the crashed ice with 1/4 kilo of rock salt;
place the can (with cover) with ice cream mixture inside the large container;
after the placing the can, put the ice and rock salt over the can alternatively until it reaches the cover or until the container is full;
Shake the container until the harden ice cream is made.

Questions:

Why did we put a salt on the ice?

answer: because salt prevents the ice from melting and "we add salt to lower the freezing point of water, from 0 degrees celsius to lower than zero. When the freezing point of water decreases, its melting point also lowers thus, the ice actually melted but the temperature is much lower than zero. Such low temperature makes the ice cream mixture to solidify.."(ma'am rhea)

Is melting exothermic or endothemic?how about freezing?

answer: Melting is endothermic because heat is absord from the surrounding to the system.

While, freezing is exothermic because heat is released from the system to the surrounding.