Experiment 3 Chm 420
Short Description
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Description
SUBJECT CODE EXPERIMENT TOPIC DATE
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CHM 420 3 Types of Chemical Reactions 17/10/2014
NAME MATRIC NO I/C NO GROUP LECTURER NAME
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NABILAH BINTI AMINUDDIN AMINUDDIN 2014805292 950320145006 AS2301M1 DR. ZURAIDA KHUSAIMI
OBJECTIVE To study the general types of chemical reaction and to write balanced equations for each time of reaction. THEORY Chemical reactions have many ways to be classified and there are several types of them. There are 4 different types of chemical reactions: combination, decomposition, displacement and metathesis. These are the examples for the types of reaction: (a) Combination reaction : When two substances ( elements or compounds ) combine to form a single product:
Example:
A + B → AB 2Na(s) + → 2NaCl(s)
(b) Decomposition reaction : Single substance decomposes into two or more simpler substances:
Example:
AB → A + B Ca (s) → CaO(s) + (g) Δ
(c) Displacement reaction : An element reacts with a compound and displaces one of the elements in the compound which is the original element becomes part of a new compound with the displaced element as a byproduct:
Example:
A + XY → AY + X Zn(s) + 2HCl(aq) → + Zn (aq)
(d) Metathesis reaction : An exchange of “par tners” between two com pounds:
Example:
AB + XY → AY + XB 2KI(aq) + Pb (aq) → 2 (aq) + Pb (s)
CHEMICALS AND APPARATUS Magnesium ribbons Sand Paper Copper Iron nail Zinc Litmus paper KCl (s) (s)
1.0M CuS 1.0M Fe 0.1 M Ag 1.0M HCl 1.0MPb 1.0M 1.0M NaOH 1.0M
Crucible and cover Bunsen burner Tripod stand Clay triangle Test tubes Wooden splint
METHODOLOGY A. Combination Reactions 1. A crucible and a cover is obtained. 2. A cleaned piece of magnesium ribbon is obtained and it is coiled until it formed a piece that small enough to rest on the bottom of the crucible, but with enough air to to get in between the coils or folds. It is very important to have as much as magnesium ribbon as possible in contact with the bottom of the crucible, as this will be the hottest part of the crucible and we want the magnesium to be really hot. 3. The crucible and its content are heated at first with brushing motion then it is heated to redness for three minutes. 4. The gas burner is switched off when the reaction is completed. B. Decomposition Reactions 1. A small amount of potassium chlorate ( in a clean, dry test tube and heat gently. The liquefied and gas bubbles is formed. 2. After one minute of heating, the wooden splint is lighted. The flame is blown out and quickly inserted the glowing splint into the mouth of the test tube as the reaction is still occurring. If the compound is still giving off oxygen, the glowing splint will ignite again. Stop heating and look carefully at the test tube.
C. Single Replacement Reaction 1. Five clean test tube is placed in a test tube rack and the test tube is numbered. 1 ml of 1.0 M CuS is put in test tube 1, 1ml of 1.0M Fe in test tube 2, 1 ml of 0.1M Ag in test tube 3, and 1ml of 1.0 M HCL in each test tube 4 and 5. 2. An iron nail is sandpapered and it is placed in test tube 1.Three pieces of copper is sandpapered and it is placed in test tube 2,3 and 4. A piece of zinc is sandpapered and it is placed in test tube 5. The test tube is set aside for 10 minutes. The test tubes is observed at the end of time. The nail from the test tube is removed and examined. If there any evidence that a reaction taken place, a balanced equation for the reaction is written. If there no such evidence, then write N.R.
D. Metathesis or Double Replacement Reactions 1. Precipitation Reaction In a clean test tube, 1ml of 1.0 M Pb solution and 1 ml of 1.0 M solution is mixed. The mixture is stirred. 2. Acid-base neutralization 3ml of 1.0 M NaOH solution is put in a clean test tube. 3ml 1.0M added carefully. 3. Formation of gas 5 ml of 1.0 M and solid in a clean test tube. A bubbling in the test tube will be observed that shows a gas is formed. The chemical reaction is written for the reaction and a confirmation of gas for the gas evolved is done. The carbon dioxide gas produced turn blue litmus paper red. It will also react with a solution of calcium hydroxide to form a precipitate.
DATA/RESULT Experiments
Observations Magnesium burns brightly and turned to white powdery solid
A: Combination Reaction
Moisture formed in the test tube. KCl melted to clear solution. Relights glowing wooden splinter. Oxygen is released and turned to white solid.
B: Decomposition Reaction
Experiment
C: Single Replacement Reaction
Observations Test tube 1 CuS + Fe iron is deposited and becomes thicker
Experiment D : Metathesis
Test tube 2 Fe +Cu
Test tube 3 Ag +Cu
Test tube 4 HCl +Cu
Test tube 5 HCl + Zn
copper copper is copper bubble gas is corrodes and deposited and corrodes and formed becomes becomes becomes thinner thinner thinner
Observation/Chemical Equations
1. Precipitate Reaction
Canary yellow precipitate is formed
2. Acid-base neutralization
The base of the test tube feels warm
3. Formation of gas
Bubbles are formed
DISCUSSION For experiment A, combination reaction, the magnesium is reacted with flame and produced magnesium oxide. From the theory, A + B → AB, which in experiment A is 2Mg(s) + (g) → 2MgO(s). The magnesium oxide produced is the powdery white observe at the end of the experiment. Next, for experiment B, decomposition reaction, potassium chlorate , K is heated. From theory, AB → A + B, which in experiment B is 2K (s) 3 (g) + 2KCl(aq). We observed that when K is heated moisture formed in the test tube, and K melted to clear solution. A lighted wooden splinter is inserted to check the presence of oxygen gas. When oxygen gas is released the clear solution turns t o white solid. In addition, for experiment C, displacement reaction, there is 5 test tubes being observed. From theory, A + XY → AY + X, is Fe(s) + (aq) → (aq) + Cu(s)( test tube 1), Cu(s) + (aq) → Fe(s) + (aq) (test tube 2), Cu(s) + 2AgN (aq) + 2Ag(s) (test tube 3), Cu(s) + 2HCl(aq) → (aq) + (g) (test tube 4) and Zn(s) + HCl(aq) → (aq) + (g) (test tube 5). For test tube 1, we observed iron is deposited and becomes thicker. For test tube 2, copper corrodes and becomes thinner. For test tube 3, copper is deposited and becomes thinner. For test tube 4, copper corrodes and becomes thinner. For test tube 5, bubble gas is formed. For experiment D, metathesis reaction, there is precipitation reaction, acid-base neutralization and formation of gas. From theory, AB + XY → AY + XB is (aq) + (aq) → (s) + 2 (aq) for precipitation reaction, NaOH(aq) + (aq) → 2 (l) + (aq) for acid-base neutralization and (aq) + (aq) → (aq) + O(l) + C (g) for formation of gas. For formation of gas, the gas produced is carbon dioxide gas, C . To prove the presence of the gas, 2 test is conducted. First test is with blue litmus paper, when carbon dioxide is present blue litmus paper will turn red. Second test is with calcium hydroxide. When carbon dioxide is present a solid precipitate of calcium carbonate will formed. This, will make the lime water cloudy. The equation for this is, Ca (aq) + C (g) → (s) + O(l). There is errors occurred when conducting the experiments. One of the errors is the test tube used is not fully dried .Next, the wooden splinter does not relights at first attempt as the lighted wooden splinter is not immediately put into the test tube and this cause the oxygen gas already released to the surrounding. Plus, the Ca solution is not prepared before hand, when sulphuric acid is added to sodium carbonate resulting a lot of carbon dioxide gas escape to the surrounding. To avoid these errors from occurring, precaution must be taken. Several precaution steps that can be taken is make sure the test tubes used must be cleaned and dried to obtain more accurate result. Next, put the lighted wooden splinter quickly into the test tube. Moreover, prepare the Ca solution beforehand before adding sulphuric acid into sodium carbonate in the test tube.
CONCLUSION For combination reaction, A + B → AB is 2Mg(s) + (g) → 2MgO(s). Next, for decomposition reaction, AB → A + B is 2K (s) 3 (g) + 2KCl(aq). Moreover, for displacement reaction, AB + XY → AY + XB is Fe(s) + (aq) → (aq) + Cu(s)( test tube 1), Cu(s) + (aq) → Fe(s) + (aq) (test tube 2), Cu(s) + 2AgN (aq) + 2Ag(s) (test tube 3), Cu(s) + 2HCl(aq) → (aq) + (g) (test tube 4) and Zn(s) + HCl(aq) → (aq) + (g) (test tube 5). Lastly, for metathesis reaction is (aq) + (aq) → (s) + 2 (aq) for precipitation reaction, NaOH(aq) + (aq) → 2 (l) + (aq) for acid-base neutralization and (aq) + (aq) → (aq) + O(l) + C (g) for formation of gas. REFERENCES Exploring Chemistry Laboratory Experiments for General Chemistry, Sharipah Ruzaini Syed Aris, Kamariah Muda, Nesamalar Kantasamy,2010,University Publication Cetre (UPENA). Chemistry 11th edition,Raymond Chang, Kenneth A. Goldsby,2014,Mc Graw Hill Education Oxford Dictionary of Chemistry sixth edition ,John Daintith,2008,Oxford University Press www.gcsescience.com
QUESTIONS 1. Experiment A : 2Mg(s) + (g) → 2MgO(s) Experiment B : 2K (s) 3 (g) + 2KCl(aq) Experiment C : Test tube 1 : Fe(s) + (aq) → (aq) + Cu(s) Test tube 2 : Cu(s) + (aq) → Fe(s) + (aq) Test tube 3 : Cu(s) + 2AgN (aq) + 2Ag(s) Test tube 4 : Cu(s) + 2HCl(aq) → (aq) + (g) Test tube 5 : Zn(s) + HCl(aq) → (aq) + (g) Experiment D : 1. (aq) + (aq) → (s) + 2 (aq) 2. NaOH(aq) + (aq) → 2 (l) + (aq) 3. (aq) + (aq) → (aq) + O(l) + C (g) 2. Test with blue litmus paper and test with calcium hydroxide, Ca 3. Generally, a chemical reaction has occurred if different compounds are produced. To physically know that a chemical change has occurred there are few variables to consider: if the substance changes colour, gives off heat, gives off light or produces bubbles. If a substance is exposed to another substance and a reaction takes place, then that is a chemical reaction.
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