Chemical Changes And Equations Lab 4l3v5w

Lee 1 Harrison Lee 1/14/13 Period 11 Malisa Ray Chemical Changes and Equations

Objectives:   

Perform four types of chemical reactions: Identify some of the products of the reactions; and, Write and balance equations for the reactions observed.

Data: Reactants Synthesis: 1. Magnesium+ oxygen+ heat 2. Magnesium+ nitrogen Decomposition: Copper(II) carbonate and limewater Single Replacement: Zinc+ Hydrochloric acid

Double Replacement: Potassium chromate+ lead nitrate

Observations Intense bright white light, white smoke

Products 1.Magnesium oxide 2. Magnesium nitride

The copper(II) carbonate turned dark, lime water became cloudy Intense bubbling, zinc disappeared, precipitate formed, heat released. When flame held against inverted test tube, there was a “pop” sound. Turned yellow, yellow precipitate began to form

Carbon dioxide and Copper(II) oxide

Conclusion: 1. Write a chemical equation for each of the reactions. A. SynthesisB. DecompositionC. Single ReplacementD. Double Replacement-

Zinc chloride and hydrogen

Potassium nitrate and lead chromate

Lee 2 2. Which of the reactions in this experiment was exothermic and which was endothermic? In the experiment, experiments C and D were exothermic, because the reactions emitted heat. Experiments A and B were endothermic, because heat was required in order for the reaction to start. 3. How can you tell if a chemical reaction has occurred? What are some distinctive changes that can be observed? How do these changes differ from physical changes? I can tell if a chemical reaction has occurred by seeing if there were bubbles (gas produced), a change in color, a precipitate formed, change in weight, or a change in temperature. These differ from physical changes because the observed changes are chemical, in which the atoms rearrange themselves in different ways, compared to a physical change in which nothing happens to the structure of molecules. 4. In Part A, Step 4, were you able to detect the presence of ammonia gas? If so, what does this result suggest? I was able to smell the ammonia gas. The result of this suggests that the magnesium nitride reacted with the water in a double replacement reaction to form gaseous ammonia and magnesium oxide.

Further Investigations: 1. In Part C, the test for hydrogen was the sound resulting when some of the gas exploded.

Do any other gases have this characteristic? If so, name one. There are other gases with the same characteristic as hydrogen, one example being methane. 2. What is meant by a reversible reaction? How do chemists indicate a reversible reaction when writing a chemical equation? A reversible reaction is a circumstance in which the products of a reaction can be able to turn back into the original reactants of a reaction. Chemists indicate a reversible chemical reaction with a symbol in place of the yield sign. 3. Prepare a table of reaction types, using Table 8-2 as a guide. List the four types of reactions, the general form for each, and select from the list below three word reactions that fit each classification. Rewrite the word equations as balanced chemical equations. Type of Reaction

General Form

Example

Synthesis

A+B→ AB

1.

Lee 3

2.

Decomposition

AB→A+B

3. 1. 2. 3.

Single Displacement

A+BC→AC+B

1. 2. 3.

Double Displacement

AB+CD→AC+BD

1. 2. 3.