Wednesday, May 18, 2011

Final Exam Review Questions #s 29 and 31

29)  5.00mL of an unknown acid is titrated using 0.100M NaOH and phenolphthalein.

a. What role does the phenolphthalein play?
Phenolphthalein is a colorless crystalline solid, also known as C2OH14O4. In an alkaline solution,
phenolphthalein turns a solid pink color. In this equation, the phenolphthalein is used as an acid-base indicator. 

b. How would you know when the titration was complete? Why is this an estimation of the equivalence point and not an exact measurement of the equivalence point? 
The endpoint is the point at which the titration is determined complete by an indicator. The endpoint is ideally the same volume as the equivalence point. The equivalence point is the volume of added titrant, when the number of moles of titrant is equal to the number of moles of analyte or some other polyprotic acids. In the classic strong acid-strong base titration, the endpoint of a titration is the point when the pH of the reactant is just about equal to seven. At this point, the solution becomes a persisting solid color as in the pink of phenolphthalein indicator. Equivalence points can only be estimated, it is not possible to find the exact measurement of the equivalence point. The equivalence point of the reaction, the point at which equivalent amounts of the reactants have reacted, will have a pH dependent on the relative strengths of the acid and base used. The equivalence point can be estimated using the following rules: 
   -A strong acid will react with a strong base to form a neutral (pH=7) solution.
   -A strong acid will react with a weak base to form an acidic (pH<7) solution.
   -A weak acid will react with a strong base to form a basic (pH>7) solution.

c. If 12.15mL of NaOH are used to complete the titration, what is the concentration of the unknown acid? 
.01215 L NaOH (1.00) = mol = .01215 mol NaOH
.01215 mol NaOH/.005 L Unknown = M 
=2.43M of the unknown acid 

31) Did we cover it all? Think of a topic or question from this past trimester that        
you think should have been covered more by this review, and respond to it. You are welcome to recycle or reformulate good questions you have seen this past trimester. If you pick a really good one, I might use it on the exam.

Question: Explain how a decrease in the vapor pressure of a solution results in an increase in its boiling point. 
The more vapor pressure forced on a solution, the easier it is for the solution to boil (lower boiling point). The less vapor pressure there is, the harder it is for the solution to boil (higher boiling point). The pressure pushes the particles of H20 to the top of the solution because they are trying to escape. When there is less pressure, the particles have so big of a desire to escape and therefore they do not boil so quickly. 

Thursday, April 7, 2011

Nuclear Chemistry- Chernobyl Disaster

About Chernobyl: Nuclear Reactors

The Chernobyl Power Complex consisted of 4 RMBK-1000 nuclear reactors. (See below for image of RMBK reactor). The first two units were constructed in 1970 and 1977 while the third and fourth units were completed in 1983. Two additional reactors were under construction during the time which the accident occurred. Approximately 3 kilometers away from the complex was the newly-founded city Pripyat, containing over 49,000 residents. The old town of Chernobyl with a population of 12,500 was around 15 km South of the reactors and the total number of inhabitants within a 30 mile radius of the Chernobyl power plants was between 115,000 and 135,000 (1).
A Soviet-designed and built RMBK-1000 nuclear reactor (1). 
Nuclear reactors use uranium rods as fuel and the heat is generated by nuclear fission. Nuclear fission is a nuclear reaction in which a massive nucleus splits into smaller nuclei while it simultaneously releases energy. Carbon dioxide gas is pumped through the reactor to take heat away and the hot gas then heats water the make the steam. The steam drives the turbines, which drive the generators. Electrical power is then successfully sent around the country (2).

Advantages and Disadvantages of Nuclear Reactors: 
Advantages (2)
  • Nuclear power costs around the same amount as coal, so it is not expensive to make
  • Does not produce smoke or carbon, so it does not contribute to the greenhouse effect
  • Produces huge amounts of energy from small amounts of fuel
  • Produces small amounts of waste
  • Nuclear power is reliable 
Disadvantages (2)
  • Nuclear reactors are potentially very dangerous
  • Power complexes must be sealed up and buried away for many years to allow radioactivity to die
  • Producing the energy itself does not have excessive costs, but ensuring safety requires lots a lot of money. 
The damaged unit 4 Chernobyl reactor building (1).  
The Accident: Explosions of 1986:
The actual accident at Chernobyl occurred during an experimental test of the electrical control system. The reactor was shut down for the routine maintenance. The operators on duty at the time had violated safety codes by switching off the important control systems and allowing the flawed reactors to reach unsafe, low-power conditions. A sudden power surge in the reactor caused an explosion of steam that broke the reactor vessel. This caused more steam to violently explode and both destroy the reactor core and damage the reactor building. A large graphite fire burned for the next 10 days, releasing many hazardous radioactive materials (4).

Immediate Impacts: Evacuations and Radiation:
According to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), the disaster at Chernobyl was the most serious accident ever to occur in the nuclear power industry. Within the first few weeks of the explosions, 30 workers had already died due to the radiation and hundreds more were injured. In 1986, authorities evacuated more than 115,000 people from areas near the reactor and within the next year relocated around 220,000 more from Belarus, the Russian Federation, and Ukraine. Ranging from 1986 to 2005, there have been over 6,000 cases of thyroid cancer found in former Chernobyl citizens who were young adults or children at the time of the disaster (4).

Long-lasting Impacts: Environmental Effects:
The long-lasting Impacts of Chernobyl were fewer than expected, but were still significant. A report done by UNSCEAR, apart from the increase in thyroid cancer after childhood exposure, no increases in overall cancer incidence or mortality have been observed that could be attributed to ionizing radiation." This basically means that a person born into the area 25 years after the disaster occurred would most likely not be affected by radiation poisoning. Only inhabitants born in the region around the time of the actual accident were in any danger of the poisoning and of thyroid cancer (3). 
Radiation poisoning not only directly affects people and animals but also affects them indirectly through the environment over time (1). 
The Aftermath: Cleaning up Chernobyl
At the nuclear power station, many attempts to remove chunks of graphite and other radioactive solids were made. Robots were first sent in to speed up the process, but quickly malfunctioned due to the high radioactivity of the area. When using robots failed to work, volunteers were sent in under the condition that they were only in the radioactive areas for 90 seconds or less. After 20-60 minutes of being in these dangerous power stations, the nervous system would have shut down and the volunteers would have been killed. The radiation levels were 15,000 times greater than any normal level a person should be around within an entire year. Any movable objects near the plant were buried underground: cars, trucks, and even soil. Nearby trees were also cut down and buried. Approximately 60,000 buildings were intensely washed with special chemicals and the roofs were often replaced (5).
Here is a photo of the Chernobyl nuclear reactor after the explosion (3).
Chernobyl vs. Fukushima Daiichi: Similarities and Differences
Russian experts have said the current disaster in Fukushima, Japan is the most serious nuclear accident since the one at Chernobyl. Thankfully, the damage caused in Japan is not expected to be nearly as detrimental as the damage caused at Chernobyl. Directly after the Chernobyl explosions, authorities tried to cover up the accident and Europe was not aware or warned of the deadly nuclear disaster until approximately 24 hours after the first explosion. This caused the immediate death of 54 people and as many as 4,000 from radiation-related illnesses. As soon as Japanese authorities were aware of the situation in Fukushima, they quickly evacuated more than 200,000 citizens. The main difference between the two nuclear blasts was the way the situations were handled. We should still be worried about the horrible disaster going on in Japan, but the effects will not be nearly as bad as they were at Chernobyl because the situation was handled carefully and responsibly (6).

Works Cited:

Balonov, Mikhail. Chernobyl Accident. World Nuclear Association, 2011. Web. 06 Apr. 2011. <://>   (1)

Darvil, Andy. Nuclear Power Summary. Darvill Inc., 2009. Web. 06 Apr. 2011. <>    (2)  

Adams, Rod. Long-term Effects of Chernobyl Debated. Adams Atomic Engines Inc., 2011. Web. 06 Apr. 2011. <>    (3)

Ray, Michael. The Chernobyl Accident: UNSCEAR's Assessments of the Radiation Effects. UNSCEAR Report Inc., 2008. Web. 06 Apr. 2011. <>     (4)

Sanders, Phillip. Chernobyl Clean-up Efforts. Oracle Think Quest, 2010. Web. 06 Apr. 2011. <>     (5) 

Matthews, Owen. Why Japans Meltdown is No Chernobyl.  The Daily Beast, 2011. Web. 06 Apr. 2011. <>     (6)