Question

Pre-Laboratory Question: Investigating Chemical Reactions

Balance each of the following equations, and classify each of the reactions by type.

Reaction Equation

Type of Reaction

1.

KClO3

→

KCl

+

O2

2.

Na

+

O2

→

Na2O2

3.

KI

+

Pb(NO3)2

→

KNO3

+

PbI2

4.

Cu

+

AgNO3

→

Cu(NO3)2

+

Ag

5.

C3H8

+

O2

→

CO2

+

H2O

+

Heat

6.

Zn

+

HCl

→

ZnCl2

+

H2

Laboratory Questions

Activity 1: Synthesis Reaction

Describe all of the signs that indicated a chemical reaction occurred.

Describe the temperature change that occurred during this reaction. Is heat required or produced during the reaction?

Describe any other changes that were observed in the steel wool. What reaction might create such a change?

Write a balanced equation for the reaction of the steel wool with oxygen. Be sure to include heat energy in the reaction.

Activity 2: Decomposition Reaction

What gases could be produced from decomposing hydrogen peroxide?

Which gas was produced?

Write a balanced equation for the decomposition of hydrogen peroxide.

Activity 3: Single-Replacement Reaction

What gases could be produced from hydrochloric acid (HCl)?

Which gas was produced?

Write a balanced equation for the reaction of magnesium with hydrochloric acid.

Why did you need to tilt the splint at a 45-degree angle?

a. Write a balanced equation for the reaction initiated by the burning splint.

b. Classify the reaction initiated by the burning splint.

Activity 4: Double-Replacement Reaction

Describe the reaction of sodium bicarbonate and vinegar.

Refer to the section in the Background titled, “Standard Tests Gaseous Products.” Use a flaming splint and a glowing splint to identify the gas above the liquid in the cup. Write the name and formula of the gas in the space provided.

Write a balanced chemical equation for this double-replacement reaction.

One of the two products of this reaction is carbonic acid (H₂CO₃), which immediately forms water and the gas you identified after exposure to the flaming and glowing splints. Write a balanced equation showing the decomposition of carbonic acid.

Activity 5: Combustion Reaction

Explain why water appears on the inside of the glass test tube.

Write a balanced equation for the combustion reaction.

Activity 6: Precipitation Reaction

Write a balanced equation for the precipitation reaction.

Which product in the above reaction is the precipitate?

Discussion Questions

Predict the product(s) of the following equations. Balance the equations, and classify each of the reactions by type.

Equation

Type of Reaction

1.

Pb(NO3)2 + Na2CO3 →

2.

C4H10

+

O2

→

3.

Zn + CuSO4

→

4.

CaCO3

Heat

→

5.

Na

+

H2O

→

6.

Ca

+

O2

→

7.

MgSO4

+

LiOH

→

8.

Al

+

NiSO4

→

9.

SO2 + H2O →

10.

HgO

Heat

→

Answer 1

Answers for Balanced equations and classification of each of the reactions by its type.

2 KClO₃ (s) --------> 2 KCl (s) + 3O₂ (g)…………………………………….Decomposition Reaction

2 Na (s) + O₂ (g) --------> Na₂O₂ (s)…………………………………………Synthesis Reaction

2 KI (aq) + Pb(NO₃)₂ (aq) --------> 2 KNO₃ (aq) + PbI₂ (s)…………….. ...Double-Replacement Reaction

Cu(s) + 2 AgNO₃ (aq) --------> Cu(NO₃)₂ (aq) + 2 Ag (s)………………. ...Precipitation Reaction

C₃H₈ (g) + 5 O₂ (g) --------> 3 CO₂ (g)+ 4 H₂O (g) + Heat……………… ..Combustion Reaction

Zn (s) + 2 HCl (aq) --------> ZnCl₂ (aq) + H₂ (g) ………………………….. Single-Replacement Reaction

Xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Answers for Laboratory Questions:

Activity 1: Synthesis Reaction:

Reaction of steel wool with oxygen.

A large amount of heat is supplied by burning pure oxygen and then steel wool burns and changes to iron oxide. Following is the balanced equation of the reaction.

4 Fe (s) + 3 O₂ (g) ==> 2 Fe₂O₃ (s)

Activity 2: Decomposition Reaction:

Oxygen is produced in the decomposition reaction of H₂O₂. Below is the balanced equation of the decomposition of H₂O₂:

2H₂O₂ (l) =======> 2H₂O (l) + O₂ (g)

Activity 3: Single-Replacement Reaction:

Balanced equation for the reaction of magnesium with hydrochloric acid

Mg (s) + 2 HCl (aq) --> MgCl₂ (aq) + H₂ (g)

As can be seen from the above equation hydrogen is produced upon reaction of magnesium      

metal with hydrochloric acid.

Holding splint at 45^o is important as it allows better supply of oxygen for the burning splint.

The reaction initiated by the burning splint can be classified as combustion reaction.

Activity 4: Double-Replacement Reaction

  Na₂CO₃ (aq) + 2 CH₃COOH (l) ------> 2 CH₃COO^-Na⁺ (aq) + H₂CO₃ (g)

H₂CO₃ (g) ---------> H₂O (l) + CO₂ (g)

The final gas generated upon reaction of sodium carbonate with vinegar (acetic acid) is carbon

dioxide and extinguishes the burning wooden splint.

Activity 5: Combustion Reaction

Example for a combustion reaction:

C₃H₈ (g) + 5 O₂ (g) --------> 3 CO₂ (g)+ 4 H₂O (g) + Heat

A combustion reaction uses oxygen to burn the fuel and emits carbon dioxide gas and water

vapour. This is the reason for appearance of water on the inside of the glass test tube.

Activity 6: Precipitation Reaction

The following reaction is an example for precipitation reaction from the above reactions.

2 KI (aq) + Pb(NO₃)₂ (aq) --------> 2 KNO₃ (aq) + PbI₂ (precipitate)

Answers for Discussion Questions:

1.       Pb(NO₃)₂ (aq) + Na₂CO₃ (aq) -----→ PbCO₃(s) + 2 NaNO₃ (aq) ………......Precipitation Reaction

2.       2 C₄H₁₀ (g) + 13 O₂ (g) ---------------> 8 CO₂ (g)+ 10 H₂O (l)+ Heat…..........Combustion Reaction

3.       Zn(s) + CuSO4 (aq) --------------> ZnSO4 (aq) + Cu (s) ………………….....Redox Reaction

4.       CaCO₃ (s)+ Heat ------------> CaO (s) + CO₂ (g)...………………………….....Decomposition Reaction

5.       2 Na (s) + 2 H₂O (l) ----------------> 2 NaOH (aq) + H₂ (g).………………........Combustion Reaction

6.       2Ca (s)+ O₂ (g)----------------------> 2CaO (s)……………………………….......Combustion Reaction

7.       MgSO₄ (aq) + 2 LiOH(aq)---> Mg(OH)₂ (s) + Li₂SO₄ (aq) ……...…................Double-Replacement Reaction

8.       2 Al (s)+ 3 NiSO₄ (aq) ------------------> Al₂(SO4)₃ (aq) + 3 Ni(s)……...............Redox Reaction

9.       SO₂ (g)+ H₂O (l)-------------------> H₂SO₃ (aq) …………………………………...Synthesis Reaction

10.   2HgO (s) + Heat --------------> 2Hg(l) + O₂ (g)………………………………….....Decomposition Reaction