Classifying reactions lab !

classifying reactions
safety reminder: wear safety glasses and use ammonia in a well-ventilated area. be sure to read science safety (link on page 1 of this lesson or page 872 in textbook)

objectives:
balance chemical equations (u4l1)
identify different types of reactions (u4l2)
describe evidence that a chemical reaction took place (u2l3)

day 1

part 1 reaction between iron and oxygen (record observations for 5 days)
materials:
small glass jar
dish with sides (a pie plate works well)
steel wool
water

procedure:
1. dip a piece of steel wool in vinegar for about 5 minutes to remove any coatings and then rinse it with water.
2. tape the piece of steel wool to the bottom of the jar.
3. fill the dish about halfway with water.
4. put the jar upside down in the dish.
5. observe the water levels in the dish and the jar and observe the steel wool in the jar for 5 days.

record your observations each day in the table below.
observations:

day|water level in dish (cm)|water level in jar (cm)|appearance of steel wool
1 | | |
2 | | |
3 | | |
4 | | |
5 | | |

analysis/conclusions:

1. balance the equation for the reaction between iron and oxygen.
+ →
2. classify the reaction that occurred between the iron and oxygen.

3. what evidence was there that a reaction took place?
part ii: reaction of hydrogen peroxide
materials:
hydrogen peroxide (1/3 cup)
small pieces of raw potato (yeast or beef liver may be substituted)
small bowl

procedure:
pour one third of a cup of hydrogen peroxide into a small bowl.
cut up several small pieces of raw potato and place them in the hydrogen peroxide.
3. record your observations.

observations:
appearance of potato and hydrogen peroxide combination


analysis/conclusion:

1. the potato (as well as yeast and beef liver) contains an enzyme called catalase, which breaks down hydrogen peroxide. balance the equation, if necessary, for the breakdown of hydrogen peroxide.
→ +

2. classify the reaction that occurred.

3. what evidence was there that a reaction was taking place?

day 2

part iii: reaction between zinc and acetic acid
materials:
a penny dated after 1983
metal file or coarse sandpaper
vinegar

procedure:

use a file or sandpaper to completely remove the copper from the edge of a penny. once the copper is removed you can see the silvery zinc that composes the core of the penny.
place the penny into a small jar of vinegar so that the penny sits upright. this will allow the hydrogen gas to readily escape and increase the rate of reaction.
allow the container to stand undisturbed for 30 minutes.
while the mixture is standing, complete steps 1 and 2 of part iv of the lab. be sure to record on the next page your observations for part iii after 30 minutes.

observations:
appearance of penny in vinegar after 30 minutes

analysis/conclusions:
1. balance the equation for the reaction between zinc and acetic acid.
+ → (ch3coo)2 +

2. classify the reaction between zinc and acetic acid.

3. what evidence was there that a reaction was taking place?

part iv: reaction between magnesium sulfate and ammonia
materials:
epsom salts (mgso4),
ammonia (nh4oh)
small jar or cup
measuring cup

procedure:
dissolve 1 teaspoon of epsom salts in a half cup of water.
add 2 teaspoons of ammonia to the epsom salts solution and stir thoroughly. record your observations.
allow the mixture to stand for 30 minutes and record your observations.

observations:

appearance after initial mixing
appearance after 30 minutes 

analysis/conclusions:
1. balance the equation for the reaction between magnesium sulfate and ammonia.
(2 points)
+ → )2so4 + (oh)2

2. classify the reaction between magnesium sulfate and ammonia.

3. what evidence was there to indicate that the epsom salts and ammonia reacted?

Answer 1) Part I (Day 1) Steel wool and vinegar experiment;

The complete balanced reaction between iron and oxygen is

Explanation : The reaction which occurred between iron and oxygen was the oxidation and reduction reaction where iron got oxidized and oxygen got reduced. The steel wool when placed in vinegar removed the upper coating on it; And when it was dipped in water the reaction began.

Answer 2) The reaction was redox (oxidation commonly for iron).

Explanation : Mainly oxidation of iron was observed as the formation of rust was the reaction product that was seen. The iron layer on the steel wool got exposed with water in presence of oxygen which developed a slight greenish or brownish layer on the surface of steel wool indicating formation of rust.

Answer 3) The evidence seen for this reaction was formation of rust on steel wool
.

Explanation : When the soaked steel wool from the vinegar was removed, the protective coating of the steel wool was removed. Which allowed the iron in the steel to form rust. Also, rusting created heat energy which increased the temperature inside the beaker
. These were the evidences that the reaction took place.

Answer 4) Part
II Reaction of Hydrogen Peroxide

1) The complete balanced chemical reaction is

Explanation :
The potato (as well as yeast and beef liver) which contains an enzyme called catalase, was broken down by hydrogen peroxide. The molecules of hydrogen peroxide when broke down produced water and oxygen as the products.

Answer 5) 2) This was an example of decomposition reaction
.

Explanation : It was clear from the reaction that the molecules of hydrogen peroxide are undergoing decomposition; as it got broken down into molecules of water and oxygen. This breaking of hydrogen peroxide is an example for decomposition reaction.

Answer 6) 3) Oxygen bubbles escaped and foam was formed
.

Explanation : A damaged enzyme may not be able to catalyze a chemical reaction. So, catalase the enzyme present in the liver helped to break down harmful hydrogen peroxide into oxygen and water. When this reaction occurred, oxygen gas bubbles were seen to get escaped and created a foam.

Answer 7) Part
III Zinc and acetic acid reaction

The complete balanced reaction is .

Explanation : Zinc reacted with the acetic acid solution and produced zinc acetate as the product. This copper penny when rubbed with sandpaper removes the outer covering of copper and exposes zinc with acetic acid so that the reaction occurs.

Answer 8) 2) This is a single displacement
reaction.

Explanation : Zinc is more reactive and it displaced the active hydrogen from the acetic acid; which is given out in the form of hydrogen gas. The formation of zinc acetate confirms the occurrence of the single displacement reaction.

Answer 9) 3) Appearance of Hydrogen bubbles.

Explanation : The evidence that showed that reaction was taking place is the presence of hydrogen bubbles. When the zinc penny was exposed to acetic acid it reacted with it. Which gave out hydrogen gas as a byproduct in the form of bubbles in the solution. This confirms the evidence that reaction was occurring.

Answer 10) Part IV Magnesium sulfate and ammonium hydroxide reaction.

The complete balanced reaction is .

Explanation : When magnesium sulfate reacts with ammonium hydroxide it forms ammonium sulfate and magnesium hydroxide as the products. The product was obtained in a precipitate form.

Answer 11) 2) This was a double displacement or it can be said as precipitate
reaction.

Explanation : It can be said as a double displacement reaction because the magnesium and ammonium ions were displaced and a new product was formed. The anions and cations exchanged in their molecules and produced new molecules. It can also be called as precipitate reaction as there was a precipitate obtained after the reaction.

Answer 12) 3) Cloudiness in the chemical reaction
.

Explanation : When the Epsom salts which contained magnesium sulfate and ammonia in ammonium hydroxide reacted, there was no changes seen. After sometime, when the reaction was allowed to settled the solution appeared to be cloudy. The precipitate was not formed quickly but it took time for the formation.

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