Tuesday, May 17, 2011

Exam Review

19. Percent Composition:
Percent composition is used to identify the unknown or new compound. It tells you the exact percentage by mass of each element in a compound.
formula:
percent composition= part mass(mass of element)/whole mass(mass of compound) x100
a.)
Ni- (33.1/41.9)x100= 79.0%
O- (8.8/41.9)x100= 21%
b.)
1. find the molar mass of each element in the compound (use periodic table)
2. find molar mass of entire formula
3. use coefficients form chemical formula to determine how many grams of each element are in total mass of one mole of the compound
percent of hydrogen:
(8.064/180.163)x100= 4.48%

31. Mole
Using moles is a reoccurring topic throughout the trimester so heres a quick review...
1 mole=6.022x10^23
used for:

• atoms
• molecules
• ions
• formula units
calculating unknown element/molar mass:
1. moles= # atoms x (1 mole/6.022x10^23)
2. molar mass= molar mass/moles
3. use molar mass to find unknown element
Molar Volume of Gases:
1 mole gas= 22.4 L
(standard temperature and pressure)

Tuesday, April 5, 2011

The Chernobyl Accident﻿
the biggest nuclear plant disaster﻿﻿﻿﻿﻿﻿﻿﻿﻿﻿﻿
 Reactor 4 after the nuclear disaster (6)
Nuclear Reactors
Electricity is produced when a nuclear reactor creates a nuclear reaction by splitting atoms of an element such as uranium. The heat generated form the nuclear reaction produces steam that powers the generator of the reactor, creating electricity. (8)
 nuclear reactor diagram (11)
click here for a nuclear reactor animation

Chernobyl Plant
 RBMK-1000 model (1)
The Chernobyl Nuclear Power Plant, located in Ukraine had four nuclear reactors. The first unit was created in 1970, the second in 1977, and the last two in 1938. The last two units were second generation units with updated safety precautions. All four of the reactors were the RBMK-1000 design, created by the Soviet Union. Several other reactors of the same design were under construction at the time.(1) Each unit was able to produced 1,000 megawatts. Together, the reactors created 10% of Ukraine's electricity.(2)

The Disaster
 unit 4 reactor (1)

On April 26, 1986, the reactor crew operating on Chernobyl 4 (unit 4 reactor) ran tests on the electrical control system to see how long the turbines could fuel power to the circulating pumps without the source form the main power supply.(1) The crew continued to operate on the reactor even after the automatic safety mechanisms had been turned off, causing the reactor to be maneuvered while it was under unstable conditions. The design of the reactor itself also contributed to the accident. When the control rods were inserted into the reactor, it caused a power surge to occur. The combination of these two factors caused the reactor to overheat and create several explosions, destroying the unit. Radioactive material from the fumes of the burning reactor were continuously for 10 days.
click here to see clips from the disaster

Solving the Problem
In an attempt to extinguish the fire, 200-300 tones of water per hour were pumped into the reactor. However, after the first day, they began to fear that this would flow into the other units and flood them. Instead, they dropped boron, sand, and clay from helicopters in order to prevent the release of radioactive particles in the atmosphere.(4)

Immediate Effects
 control zones (7)
The disaster released more than 5% of the reactor core into the atmosphere, and the explosions from the reactor killed 2 workers that night.(1) On the first day of the accident, an estimated 1000 reactor workers were exposed to a high amount of radiation. More than 200,000 emergency workers were also exposed throughout the next year. About 5 million people living in Ukraine, Russia, and Belarus were also contaminated. There were also 4,000 cases of thyroid cancer following the accident.(10)

Long Term Effects
 cycle of human radiation exposure (1)
Other than an increase in of thyroid cancer among the people living in the contaminated areas, the
United Nations Scientific Committee on the Effects of Atomic Radiation(UNSCEAR) claims that "there is no evidence of a major public health impact attributable to the radiation exposure 20 years after the accident." However the land near the disaster still suffers from the effects from radiation. In 1986, 116,00 people were evacuated the contaminated area surrounding Chernobyl which is still restricted at this time.(1)

Fukushima vs. Chernobyl
 Fukushima power plant (12)
Although Fukushima and Chernobyl are being compared as nuclear plant disasters, the situation in Japan is not as dangerous as it was in Chernobyl. The two incidents are actually quite different. Unlike Chernobyl, the nuclear reactor accident in Fukushima was caused by the natural disaster of the earthquake and tsunami. Chernobyl's disaster was a result of the workers' carelessness along with a design flaw. The design for the reactors in Fukushima are more stable, and the situation is being handled with more knowledge and experience with nuclear radiation.

Pros vs. Cons of Nuclear Power
benefits:
• little pollution- "clean energy"
• energy dependancy
dangers:
• radiation- negative affects on environment/health
• expensive

images/works cited

Tuesday, January 25, 2011

Chemistry in Life

Covalent Compound Haiku
entitled "Group Effort!"

multiple atoms
share electrons to obtain
noble gas configs
Molecular Shapes
here are some examples of similar shapes as molecular shapes in everyday objects...
linear- hockey stick
bent- laptop
trigonal planar-body shape of yoga pose (warrior pose)
tetrahedral- tripod
trigonal pyramidal- tricycle

Saturday, December 11, 2010

Would My Cat Eat This?

Chemistry is everywhere!
Here are some examples of ionic compounds in everyday foods and items...

1.) sodium phosphate
found in macaroni and cheese
$Na_{3}PO_{4}$
2.) calcium phosphate
found in macaroni and cheese
$Ca_{3}(PO_{4})_{2}$
3.) sodium chloride (salt)
found in macaroni and cheese
$NaCl$
4.) hydrochloride
found in Quaker oatmeal
$HCl$
5.) calcium carbonate
found in Quaker oatmeal
$CaCO_{3}$
6.) sodium sulfate
found in bodywash
$Na_{2}SO_{4}$
7.) sodium hydroxide
found in bodywash
$NaOH$
8.) potassium carbonate
found in ramen noodles
$K_{2}CO_{3}$
9.) sodium carbonate
found in ramen noodles
$Na_{2}CO_{3}$
10.) zinc acetate
$Zn(C_{2}H_{3}O_{2})_{2}$
the other 10 ionic compounds are on Katherine's blog here:
http://www.katherineschemistryblog.blogspot.com/

Friday, November 12, 2010

Examples of Mixtures

Homogenous mixtures(evenly distributed throughout):
1. milk
2. coffee
3. salt water
4. air
5. honey

Heterogeneous mixtures(not uniform):
1. trail mix (the m&ms, peanuts, and raisins)
2. vegetable soup (different vegetables inside the soup)
4. dirt/sand (different chunks of dirt/particles in sand)
5. entire ocean (animals, plants, etc living in the ocean)

Tuesday, October 5, 2010

Gold Foil Experiment

Rutherford's Gold Foil Experiment

(1)
The gold foil experiment (aka Geiger-Marsden experiment) was created by Hans Geiger and Earnest Marsden under Ernest Rutherford in 1911 to explain the structure of an atom. The researchers used the laboratory at the University of Manchester to prove the plum pudding model. However, their surprising results disproved the theory and led to the creation of the Rutherford model.(4)
 Ernest Rutherford(8)
Ernest Rutherford is called the "father of nuclear physics." He won the Nobel Prize in chemistry in 1908 for working with radioactive substances but is most famous for revising the model of the atom. His gold foil experiment disproved the plum pudding model proposed by J.J. Thomson, Rutherford's former professor.(7)
 (2) above: plum pudding model below: gold foil experiment
The plum pudding model was created in 1904 by J.J. Thomson, a physicits who discovered the electron with a cathode ray tube in 1897. He believed that the negatively charged electrons were embedded in a sphere or cloud positively charged matter.(5)
The Experiment

Rutherford, Geiger, and Marsden shot alpha particles (positively charged particles) at a gold foil surrounded by fluorescent screen. According to Thomson's plum pudding model, positive and negative charges were distributed evenly within the atom. Because of this model, Rutherford and his colleagues believed that most of the alpha particles would pass through the gold foil. To their surprise, a small percent of of the particles were deflected at various angles.(6)
The Results

Because the alpha particles were impacted at very high velocities and large angles, it had to be hitting an extremely dense center. Rutherford concluded that the dense center held most of the atom's mass and consisted of protons and neutrons while the electrons orbited the nucleus. This explained why most of the alpha particles passed the empty space that the electrons circled and a small percent of particles reflected when they hit the nucleus.
 (3) Rutherford's model
The Rutherford Model
Rutherford created a new model of the atom with the positively charged nucleus, containing protons and neutrons, as the center and negatively charged electrons orbiting the nucleus.(6) He believed that the centripetal force of the revolving electrons was generated by from the electrostatic force of attraction between the nucleus and electrons.(10)
Flaws in Rutherford's Theory
1) Because of the electromagnetic waves theory, the electrons orbiting the nucleus could not have centripetal force without becoming unstable.
2) Despite what Rutherford believed, the atoms could not radiate a constant spectrum of electromagnetic waves.
The Importance
From their experiment, Rutherford and his colleagues discovered the nucleus of an atom. The results of the gold foil experiment replaced the plum pudding model with a more accurate model of an atom. The Rutherford model gives a representation of how protons, neutrons, and electrons are arranged in an atom.

Works Cited
1.http://wps.prenhall.com/wps/media/objects/602/616516/Chapter_02.html
2.http://commons.wikimedia.org/wiki/File:Rutherford_gold_foil_experiment_results.svg
3.http://www.daviddarling.info/encyclopedia/R/Rutherfords_experiment_and_atomic_model.html
4.http://en.wikipedia.org/wiki/Geiger–Marsden_experiment
5.http://www.britannica.com/EBchecked/topic/593128/Thomson-atomic-model
6.http://micro.magnet.fsu.edu/electromag/java/rutherford/