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? 

L(M)=mol

.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. 

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. <://www.world-nuclear.org/info/chernobyl/inf07.html>   (1)

Darvil, Andy. Nuclear Power Summary. Darvill Inc., 2009. Web. 06 Apr. 2011. < http://www.darvill.clara.net/altenerg/NucPowerSummV2.pdf>    (2)  

Adams, Rod. Long-term Effects of Chernobyl Debated. Adams Atomic Engines Inc., 2011. Web. 06 Apr. 2011. <http://atomicinsights.com/2001/04/longterm-effects-of-chernobyl-debated.html>    (3)

Ray, Michael. The Chernobyl Accident: UNSCEAR's Assessments of the Radiation Effects. UNSCEAR Report Inc., 2008. Web. 06 Apr. 2011. < http://www.unscear.org/unscear/en/chernobyl.html>     (4)

Sanders, Phillip. Chernobyl Clean-up Efforts. Oracle Think Quest, 2010. Web. 06 Apr. 2011. <http://library.thinkquest.org/3426/data/emergency/cleanup.efforts.html>     (5) 

Matthews, Owen. Why Japans Meltdown is No Chernobyl.  The Daily Beast, 2011. Web. 06 Apr. 2011. <http://news.yahoo.com/s/dailybeast/20110314/ts_dailybeast/12907_whyjapansnuclearmeltdownisnochernobyl>     (6) 

Household Ions

Key: 
A. Compound Name
B. Compound Formula 
C. Name of the household item the compound is found in 

1)
   A. Disodium Phosphate
   B. Na₂PO₄
   C. Betty Crocker Mashed Potatoes: 
2)
   A. Sodium Bisulfite 
   B. NaSO₃
   C. Betty Crocker Mashed Potatoes
3) 
   A. Sodium Flouride
   B. NaF
   C. Colgate Toothpaste 
4) 
   A. Potassium Chloride
   B. KCl 
   C. Orville Redenbacher's Popcorn
5)
   A. Calcium Carbonate 
   B. CaCO3   
   C. Rice Chex Cereal 
6)
   A. Calcium Phosphate 
   B.  CaPO₄
   C. Honey Maid Grahm Crackers 
7)
   A. Sugar
   B. C₆H₁₂O₆
   C. Honey Maid Grahm Crackers 
8) 
   A. Sodium Phosphate 
   B. NaPO₄
   C. Macaroni & Cheese 
9) 
   A. Ferrous Sulfate 
   B. FeSO4
   C. Macaroni & Cheese  
10)  
   A. Iron Oxide 
   B. FeO
   C. Milk-Bone Dog Biscuits 
11) 
   A. Dicalcium Phosphate  
   B. Ca2PO4  
   C. Milk-Bone Dog Biscuits 
12)
   A. Sodium Chloride 
   B. NaCl
   C. Opti-Free Contact Solution 
13)
   A. Water 
   B. H2O
   C. Febreeze Air Freshener 
14)
   A. Titanium Dioxide 
   B. TiO2
   C. Zyrtec Allergy Pills 
15) 
   A. Magnesium Chloride: 
   B. MgCl2
   C. Bedhead Shampoo 
16) 
   A. Sodium Nitrate 
   B. NaNO3
   C. Pepperoni
17) 
   A. Zinc Oxide 
   B. ZnO
   C. Nutri-grain Bar 
18) 
   A. Calcium Hydroxide 
   B. Ca(OH)2    
   C. Orange Juice 
19)  
   A. Magnesium Oxide 
   B. MgO 
   C. Peanut-butter 
20) 
   A. Ammonium Chloride 
   B. NH4Cl
   C. Bedhead Conditioner
   

FINAL review question #16

Question:
How did Thomson determine that the cathode ray was negatively charged?

Answer:
In 1897, the electron was discovered by an English physicist named J. J. Thomson. An electron is a negatively charged subatomic particle. To discover the electron, Thomson experimented by passing electric currents through gases at low pressures. The gases were sealed in glass tubes that were closed at the ends by two electrodes, or metal disks. The electrodes were connected to a source of electricity. One electrode was positively charged and one electrode was negatively charged. The positively charged electrode was called an anode and the negatively charged electrode was called a cathode. The result of the two electrodes was a cathode ray, or a glowing beam, that traveled from the cathode to the anode. A cathode ray is deflected by a magnet. It is also deflected by electrically charged metal plates. The cathode ray is attracted by the positively charged plats, and is repelled by the negatively charged plate. Thomson knew when conducting this experiment that opposite charges attract and negative charges are repelled from each other. Thomson hypothesized that a cathode ray is a stream of tiny negatively charged particles moving at a high speed. Thomson originally referred to these particles as corpuscles, but they were later renamed as electrons. J. J. Thomson set of an experiment to measure the ratio of the charge of an electron to its mass so he could prove his hypothesis. It was discovered that the ratio was constant and the charge-to-mass ratio of electrons did not depend on the type of gas in the cathode-ray tube or the type of metal used for the electrodes. Thomson was able to conclude from his experiment that electrons must be parts of the atoms of all elements.

The Discovery of Neutrons

Important Definitions:

Neutron: an elementary particle with 0 charge and mass about equal to a proton; enters into the structure of the atomic nucleus.  

Electron: an elementary particle with a negative charge equal to the positive charge of an electron.

Proton: an elementary particle with a positive charge equal to the negative charge of an electron.

Quark: any group of six elementary particles having electric charges of a magnitude one-third or two-thirds that of the electron.

Alpha particle: a positively charged particle, indistinguishable from a helium atom nucleus and consisting of two protons and two neutrons.

Isotope: one of two or more atoms with the same atomic number but with different numbers of neutrons.

Beta decay: radioactive decay of an atomic nucleua that is accompanied by the emmision of a beta particle.

Beta particle: a high-speed electron emitted in the decay of a radioactive isotope.
Polonium: a radioactive metallic element that has simillar qualities as bismuth.

What is a Neutron?

A neutron is a tiny suatomic particle that can be found in almost all forms of matter (3). The only stable exception where a neutron is not found is in a hydrogen atom (3).The neutron is located in the atomic nucleus, and it is bound with protons through a strong nuclear force (3). The term "neutron" is used because it has no electrical charge and is therefore neutral (3). A neutron is the result of the combination of a proton and an electron (3). Because a proton has a positive charge equal to the negative charge of an electron, the two are attracted to each other and together they form a neutron (3). Most atoms have an equal number of protons and neutrons in their nucleus (3). However, when this balance is broken, the atom becomes an isotope (3). Neutrons can survive ouside of the nucleus for about 15 minutes, before they undergo beta decay and break down into protons and electrons (3).

Neutrons vs. Protons

Protons: 

Slightly lesser masses than neutrons (2).

Composed of two up quarks and one down quark (2).  

Extremely stable outside the nucleus; takes a long time to decay (2).

Discovered by Ernest Rutherford in 1919 (2).

Used to treat cancer (2).

Neutrons:  

Slightly greater masses than protons (2).

Composed of two down quarks and one up quark (2).
Extremely unstable outside the nucleus; decay within 15 minutes (2).

Discovered by James Chadwick in 1932 (2).

Used to create weapons of mass destruction (2).

The Discovery of the Neutron

In 1920, Ernest Rutherford had suggested the idea of an electrically neutral particicle when he was trying to explain for isotopes of hydrogen (4). In 1930, Charles Chadwick performed an experiment that would lead to the discovery of neutrons (4). When alpha rays emitted from polonium were fired at light nuclei, the alpha rays gave rise to the penetrating rays and no electric charge could be found (4). The "penetrating rays" were considered gamma rays (4). When a beryllium target was used instead, the rays were even more penetrating than when other targets were used (4). Chadwick was able to conclude that the mysterious radiations did not have any electric charge because it was not affected by how close it was to a magnetic field (5). Gamma radiation involved the photoelectric effect, and these rays did not, so these rays could not possibly be gamma rays (5). The photoelectric effect occurs when protons stike certain surfaces and produce electrons (5). Instead of doing this, the mysterious rays discharged protons (5). This fact also proved that the particles had greate masses than chemists had formerly thought they did (5). In 1931, Chadwick proposed the thought that the neutral rays were concrete evidence of the idea that neutrons existed (4). James Chadwick received the Noble Prize in 1935 for his discovery of the neutron (5).

Affects of the Neutron

The discovery of the neutron changed subatomic physics forever and allowed scientists to discover new elements (4). It also led the discovery of nuclear fission and is used to create nuclear weapons (4). Charles Chadwick was the leader of the British technical team during World War II, and he helped the U.S. invent the atomic bomb (4). The U.S. used this nuclear weapon to attack Hiroshima and Nagasaki, Japan and to defeat Japan in World War II (4).

Characteristics of Neutrons

-Subatomic particles found in nucleus of atoms, along with protons (1).

-No electrical charge (1).

-Mass = 1.6749 X 10 ^-27 kg, or 1,840 times the mass of an electron (1).

-Consists of three quarks: one up quark and two down quarks (1).

-Only stable when bound in atomic nucleus (6).

-Lifetime of free neutron is 886 approximately seconds (6).

-Only neutral to outside; have inner structure with distribution of + and - charges (6).

-Has a spin, or an inner angular momentum (6).

-Can adjust its spin in magnetic field (6).

-Can pass through massive layers with thickness of several centimeters (6).

-Can induce nuclear reactions (6).

Click Here for a Video...

Click Here for a Video...

Works Cited

(1) Wolfe, Kari. Characteristics of a Neutron. eHow Inc., 1999. Web. 07 Oct. 2010. <www.ehow.com/about_5386862_characteristics-neutron.html>

(2) Weiner, Stephen. Protons vs. Neutrons. eHow Inc., 1999. Web. 07 Oct. 2010. <www.ehow.com/about_5434576_protons-vs-neutrons.html>

(3) Anissimov, Michael. What is a Neutron? Conjecture Corporation, 1999. Web. 07 Oct. 2010. <www.wisegeek.com/what-is-a-neutron.htm>

(4) James Chadwick. Creative Commons Attribution, 2008. Web. 07 Oct. 2010. <www.newworldencyclopedia.org/entry/James_Chadwick>

(5) McPhee, Isaac M. The Discovery of the Neutron. Isaac M. McPhee, 2008. Web. 07 Oct. 2010. <www.suite101.com/content/the-discovery-of-the-neutron-a46060>

(6) Properties of Neutrons. Frank Laboratory of Neutron Physics, 2008. Web. 07 Oct. 2010. <http://flnp.jinr.ru/375/<http://flnp.jinr.ru/375/>

Physical and Chemical Properties of Marshmallows

     I chose to experiment with the chemical and physical properties of marshmallows because I decided it would be a fun, interesting, and safe experiment. I discovered five chemical properties and six physical properties of marshmallows. I tested four marshmallows for this experiment, and also included a fifth additional marshmallow that I left in it's original condition. First, I microwaved Marshmallow #1 for 30 seconds. The marshmallow expanded to roughly the size of a teacup and much of the marshmallow turned a brownish color. With Marshmallow #2, I placed it in a cup of hot water and after about three hours, it finally dissolved. Next, I put Marshmallow #3 in the freezer for two hours and it completely hardened. When I removed Marshmallow #3 from the freezer, i was able to use a hammer against it about five times before parts of the marshmallow began to crumble. Finally, I used a metal utensil to light Marshmallow #4 on fire. The marshmallow proceeded to turn black and the texture turned rough. The flame shut itself out, but not before the marshmallow had been burned. The chemical properties I observed include: 1) The ability to expand when heated (change in temperature); 2) The ability to change color when heated; 3) The ability to dissolve in hot water; 4) The ability to freeze; and 5) The ability to burn. The physical properties I observed include: 1) Color: white; 2) Density: marshmallow is less dense than water; 3) Conductivity: extremely poor; 4) Attraction to magnets: non-existent; 5) Malleability: slightly malleable when frozen; and 6) Hardness: very soft.

The following is an image containing the results of the experiment: