Essay of Burette and Burette clamp

Burette and Burette Clamp

There are many chemical apparatus in the laboratory. All of them have specific and different form, function, and material. This essay will explain two chemical apparatus, namely burette and clamp.

Burette is cylindrical glass tube with measurements marked on the side and a stopcock at the bottom. This apparatus is used to accurately measure the volume of liquid before releasing it to another container. Acid-base titration is one process that uses burette. The burettes have four sizes. The first one is the small one, which has 580 mm length that can be filled 10 ml liquids. The second one has 650 mm length that can be filled 25 ml liquid. The third one has 850 mm length that can be filled 50 ml liquid. And the last one has 885 mm length and can be filled 50 ml liquid. Based on the four sizes, burette is thin and long. It is easy to be broken. Therefore, it needs special maintenance. The burette must be taken very carefully to prevent it from hitting something and being broken. After using it, the burette must be washed completely, especially the stopcock. Stopcock is a very small tap. If the stopcock is not washed completely, it will be clogged by some chemicals, and can not be repaired.

Burette Clamp is apparatus to hold burette. Generally, the burette is made of alloy but some burette is made of iron. There are two types of burette clamp. The first is one burette clamp, which has one clamp that only can hold one burette. The second is two burette clamp, which has two clamps to hold two burettes. The burette clamp has no special maintenance, but this apparatus must be taken carefully to prevent it from damage.

Based on the explanation above, burette and burette clamp have their own properties and important functions. Both of them support each other and must be taken carefully for the success of experiment.

REFERENCES

Anonymous. http://en.wikipedia.org/wiki/burette  (accessed on 23^th February 2012 at 7.20 AM)

Bureau of Secondary Educ.-.Module 2 : Laboratory Apparatus, Safety Rules and Symbols. Department of Education DepEd Complex, Meralco Avenue Pasig City

Essay of Carbon Tetrachloride

Carbon Tetrachloride

Element is the basic component of the matter. They can be mixed into mixture and react each other and turn into compounds .Compounds consists of two or more different elements and have certain properties. One of them is Carbon tetrachloride. This compound is very useful but it still has many dangers. Therefore, knowing it properties is one important thing in using the compound optimally, orderly and safely. This essay will discuss deeply about this compound.

Carbon Tetrachloride is organic compound with the formula CCl₄. This compound also known by many other names like Tetrachloromethane, Benziform, Benzinoform, Carbon chloride, Carbon tet, Freon 10, Halon 104, Methane tetrachloride, Perchloromethane, Tetraform and Tetrasol (Wikipedia, 2012). CCl₄ is one of covalent compound and absolutely has covalent bond. Carbon atom, as a central of the molecule, bonds the four chlorine atoms. The carbon atom has four valence electrons, and the chlorine atom has seven valence electrons. In order to follow the octet rule, only one of the seven valence electrons of chlorine is shared to the carbon atom. The bond between carbon and the four chlorine atom is showed by dot Lewis structure below.

The Dot Lewis structure show that four chlorine atoms are positioned symmetrically as corners in a tetrahedral configuration joined to a central carbon atom by single covalent bonds. Because of this symmetrical geometry, CCl₄ is non-polar. The molecule model below show the length bond between C and Cl is 1.78Å and the bond angle of each Cl-C-Cl is 109.5° or known as tetrahedral.

Physically, CCl₄ is a clear, colorless, sweet odor and non-flammable. It is miscible with most aliphatic solvents and itself is a solvent, the molecular weight is 153.8 g/mol, density is 1.5867 g/cm³ in liquid form, boiling point is 76.7°C, melting point is -23°C, solubility is soluble in acetone, ethanol, benzene and carbon disulfide. CCl₄ is very toxic. Drink water that contain CCl₄ damages the liver and kidneys. Other symptoms include headache, dizziness, tiredness, weakness and blurred vision. Very high doses can also cause vomiting, stomach pain or death. Breathing carbon tetrachloride may seriously damage the liver and kidneys. Other possible effects are headache or dizziness, tiredness or lightheadedness. Some people breathing carbon tetrachloride seem dazed. Breathing carbon tetrachloride can also cause vomiting and stomach pain. Breathing high doses causes lung damage and death.

 CCl₄ was originally synthesized by the French chemist Henri Victor Renault in 1839 by the reaction of chloroform with chlorine, but now it is mainly produced from methane (Wikipedia, 2011).

CH₄ + 4 Cl₂ → CCl₄ + 4 HCl

The production often utilizes by-products of other chlorination reactions, such as from the syntheses of dichloromethane and chloroform. Higher chlorocarbons are also subjected to "chlorinolysis:"

C₂Cl₆ + Cl₂ → 2 CCl₄

Prior to the 1950s, carbon tetrachloride was manufactured by the chlorination of carbon disulfide at 105 to 130 °C:

CS₂ + 3Cl₂ → CCl₄ + S₂Cl₂

CCl₄ is one of non-polar solvent which generally found as liquid at room temperature. However, in solid form it may be found absolutely by decreasing the temperature. There is transition phase when it is in solid to liquid forms. That phase creates two type of its crystal structure i.e. monoclinic to rhombohedral (Nedelec et all. 1998). Generally the monoclinic and rhombohedral crystal structure shown as follows

Generally the tendency of tetrahedral when it forms crystal structure is become the lattice of its crystal. It means the crystal structure of CCl₄ in solid or liquid form is arranged by each molecules of CCl₄ symmetrically.

Carbon tetrachloride is used in the synthesis of chlorinated organic compounds, including chlorofluorocarbon refrigerants. It is also used as an agricultural fumigant and as a solvent in the production of semiconductors, in the processing of fats, oils and rubber and in laboratory applications.

Based on the explanation above carbon tetrachloride is very useful but it still has many dangers. Knowing and understanding the chemical and physical properties of CCl₄ is one way to wisely  take care this compound. Maximize the benefit of CCl_4, and minimize the dangers when use it.

REFERENCES

Anonymous. http://en.wikipedia.org/wiki/Carbon_tetrachloride (accessed on 23^th February 2012 at 7.20 AM)

Chang, Raymond. 2008. General Chemistry : The Essential Concepts Fifth Edition. New York : Mc Graw Hill

Effendy. 2008. A-Level Chemistry for Senior High School Students Volume 1B. Malang : Bayumedia Publishing

Delaware Health and Social Service. 2009. Carbon Tetrachloride.

Nedelec et all.1998. Crystallization of Carbon Tetrachloride in Confined Geometries. Ecole Nationale Supérieure de Chimie de Clermont Ferrand & Université Blaise Pascal, 24 Avenue des landais 63177 Aubière Cedex, France

A Simple Identification of Chemical Reactions

1.        Titles

The Identification of Chemical Reactions

2.      Objectives

To Identify the chemical reactions

3.      Theory

Such basic (intrinsic) characteristics consist of a substance’s color, odor, solubility and state of matter (that is, is it a solid, liquid, or gas at room conditions). Thus, these indicators reflect a change in one or more of these attributes. In this activity, we will explore several indicators using solutions of two substances that will be added together. If two solutions are poured together and an indicator is observed, then we conclude that a new substance has been produced and that a chemical reaction has taken place. Those indicators are:

1. Change in color. Here the color change must not be merely a dilution of a

beginning color (like diluting blue food coloring with water). A different color or a definite hue change must occur.

2. Change in odor. Although this characteristic seems obvious, it is often hard to detect. The proper way to smell a substance is to hold the test tube or container 4-6 inches from the nose and waft (fan) the air above the container towards the face.

3. Formation of a gas. If a substance is a solid under room conditions and is

changed to a new substance that is a gas at room temperature, then this new

substance can be detected by bubbling or fizzing of a solution. (Note that this is without the addition of heat.)

4.      Formation of a precipitate. If a substance is soluble in water and is changed to a new substance that is insoluble, a solid will appear in the solution. Some precipitates are quite dense and settle quickly to the bottom of the container. The  Rules of solubility ionic compounds  of ionic compounds is showed below in the back of this report. Others are small, finely divided particles that settle slowly and make the solution appear cloudy. Any interference with light passing through a liquid is indicative of particles floating in the liquid and dispersing the light yso that the liquid is no longer transparent.

5.        Materials

1.      100 ml of water 2.      0,585 gram of Solid of NaCl 3.      HCl 0,1 M 4.      NaOH 0,1 M 5.      AgNO3 0,1 M

6.      Pb(NO3)2 0,1 M 7.      KI 0,1 M 8.      Na2SO4 0,1 M 9.      BaCl2 0,1 M

6.      Equipments

Volumetric flask (1) Termometer (1) Test tube (5) Electrical Balance (1) Watch glass (1)

Spatula (1) Stirring Rod (1) Test tube rack (1) Beaker Glass (2)

7.        Procedures

1. First, I and my my friends prepared a solution as the materials of the lab work. I prepared 100 ml of NaCl 0,1 M by dissolve 0,585 gram of solid NaOH.
2. After the solutions has already done,  The chemical identification is started.
3. First Reaction, HCl_(aq) + NaOH_(aq), A Test tube is taken and filled with ± five drops of HCl. And then , the NaOH is filled  ±  five drops into same test tube. And then the test tube is observed.
4. Second Reaction, A Beaker glass 100 ml is fulfilled  by  water. And the A little cut of solid Sodium is placed on the water slowly. And then, the reaction is
5. The third reaction, AgNO_3(aq) + NaCl_(aq) A Test tube is taken and filled with ± five drops of AgNO₃. And then , the NaCl is filled  ±  five drops into same test tube. And then the test tube is observed.
6. The fourth reaction, Pb(NO₃)_2(aq) + KI_(aq), A Test tube is taken and filled with ± five drops of , Pb(NO₃)₂. And then , the KI is filled  ±  five drops into same test tube. And then the test tube is observed
7. The fifth reaction, Na₂SO_4(aq) + BaCl_2(aq), A Test tube is taken and filled with ± five drops of , Na₂SO₄. And then , the BaCl₂is filled  ±  five drops into same test tube. And then the test tube is observed

8.        Results

No	Reactions	Before mixed	After Mixed
1	HCl(aq) + NaOH(aq)	Both of the solution is colorless	·         Temperature changed, from 30o C into 31o C
2	Na(s) + H2O(l)	The solid sodium has a grey color	·         Temperature changed, from ·         Bubbles is produced ·         The odor changed
3	AgNO3(aq) + NaCl(aq)	Both of the solution is colorless	·         White Precipitate is formed ·         The color  changed, from colorless to white
4	Pb(NO3)2(aq) + KI(aq)	Both of the solution is colorless	·         Yellow precipitate is formed ·         The color changed, from colorless to yellow
5	Na2SO4(aq) + BaCl2(aq)	Both of the solution is colorless	White precipitate is formed The color  changed, from colorless to white

9.      Discussions

1.      HCl_(aq) + NaOH_(aq) à NaCl_(aq) + H₂O_(l). This reaction is happened in the first reaction. The temperature change is occurred because this reaction is belong to exothermic reaction and follow a chemical equation :

HCl_(aq) + NaOH_(aq) à NaCl_(aq) + H₂O_(l)  Δ H = -x. The chemical reaction is known by the change of the temperature

2.      Reaction between Solid sodium with water produce sodium hydroxide and hydrogen gas, follow a chemical equation :

2Na_(s) + 2H₂O_(l) à 2NaOH_(aq) + H_2(g)  ΔH = -x. the reaction is exothermic reaction, because of that, the temperature change. The hydrogen gas is released in bubble form.

3.      Reaction between Silver nitrate with salt produce a precipitate forms of silver chloride and a solution of sodium nitrate,  follow a chemical equation :

AgNO_3(aq) + NaCl_(aq)àAgCl_(s) + NaNO_3(aq)

The precipitate forms because the solid (AgCl) is insoluble in water, that follow a chemical equation :

Ag⁺_(aq) + Cl^-_(aq) à AgCl_(s)

 That is true for all precipitates - the solids are insoluble in aqueous solutions. The color change follow the color of the new compounds. So, the chemical reaction happen if there is a change in color and a formation of precipitate

4.      Reaction between Lead nitrate with Potassium Iodide produce a precipitate forms of Lead iodide and a solution of potassium nitrate,  follow a chemical equation :

Pb(NO₃)_2(aq) + KI_(aq)à PbI_2(s) + KNO_3(aq)

The precipitate forms because the solid (PbI₂) is insoluble in water, that follow a chemical equation :

Pb²⁺_(aq) + 2I^-_(aq) à PbI_2(s)

 That is true for all precipitates - the solids are insoluble in aqueous solutions. The color change follow the color of the new compounds. So, the chemical reaction happen if there is a change in color and a formation of precipitate

5.      Reaction between Sodium Sulphate with Barium Chloride produce a precipitate forms of Barium Sulphate and a solution of Natrium chloride,  follow a chemical equation :

Na₂SO_4(aq) + BaCl_2(aq) à BaSO_4(s) + NaCl_(aq)

The precipitate forms because the solid (BaSO₄) is insoluble in water, that follow a chemical equation :

Ba²⁺_(aq) + SO₄^2-_(aq) à BaSO_4(s)

That is true for all precipitates - the solids are insoluble in aqueous solutions. The color change follow the color of the new compounds. So, the chemical reaction happen if there is a change in color and a formation of precipitate

10.  Conclusions

The Indicators of  Chemical Reactions are :

1.      Change in temperature         2.      Change in Odor 3.      Change in color

4.      Formation of gas 5.      Formation of precipitate

11.  References

Moore, John T.2003. Kimia for Dummies. Bandung : Pakar Raya

Subagia, I Wayan.2005.Buku Penuntun Kimia Dasar I. Singaraja : IKIP Negeri Singaraja

Subagia and Suheimi. 2005. Materi Praktikum Kimia Dasar I. Singaraja : IKIP Negeri Singaraja