Experiment 6 – Types of Reactions Name __________________
Lab Section __________________
Experiment 6 - Types of Reactions
Introduction
There are six basic reactions in chemistry: combination, decompositions, single replacement, double replacement, neutralization, and combustion. This lab will demonstrate all of these reactions, except combustion.
In general, each of these reactions can be thought of as follows:
Combination: A + X → AX
Where, on the reactant side, A and X are two elements, or an element and a compound; and on the product side a new compound is formed (physical states can vary).
Decomposition: AX → A + X
Where, on the reactant side, AX is a compound; and on the product side, A and X are elements or new compounds (physical states can vary).
Single Replacement: A s+ BXaq → Bs or g+ AX(aq)
Where, on the reactant side, A is an element (usually a solid) and BX is an solution; and on the product side B is the other element (usually a solid, but can also be a gas, depending on that element’s natural physical state) and AX is a new solution.
Double Replacement: AX aq+ BZaq → AXaq+ BZ (s)
Where, on the reactant side, AX and BZ are aqueous solutions; and on the product side, a precipitate (solid) and a new aqueous solution are formed.
Neutralization: HA aq+ BOH aq → ABaq+ HOH (l)
Where, on the reactant side, HA is an acid and BOH is a base; and on the product side, AB is an aqueous salt solution and liquid water is formed. This water is often written as HOH instead of the familiar H2O, as it aids in balancing the reaction. This is merely a convention.
Combustion: CxHyOz + O2g → CO2g + H2O (g)
Where, on the reactant side, CxHyOz is a hydrocarbon (a compound containing carbon and hydrogen and sometimes oxygen in a stoichiometric ratio) and oxygen; and on the product side, CO2 and water are formed (stoichiometry will vary).
It is important that the physical states of these reactants and products be identified in the chemical equation. Using the symbols (s), (l), (g), and (aq), the physical states can be denoted as solid, liquid, gas, and aqueous, respectively. These physical states are usually determined by observation, though later on predictions can be made using certain guidelines (as in the cases of single, double, and neutralization reactions).
It is useful to note that products of a combination reaction can usually be determined by the reactants involved, especially if the reactants are a metal and a nonmetal (two nonmetals is much more difficult). In this case, it is important to remember to balance the charges of the respective ions that would form the final product. For instance,
Al s + O2g → Al2O3 (s)
Knowing that aluminum is Al3+ and oxygen is O2-, the least common multiple, 6, is identified. This means that 2 Al3+ will combine with 3 O2- to form Al2O3. This creates a charge neutral compound. The overall reaction can then be balanced by ensuring that the total number of each of the atoms on the reactant side and the product side are equal. (note, the above reaction is, of course, not balanced, but could easily be done)
For the decomposition reactions, there are really only a handful of reactions in which the products can be predicted. Two of these reactions are the decomposition of the metal hydrogen carbonate and the metal carbonates. These are usually done using heat. In general these reactions follow these rules:
MHCO3 s → MCO3s + H2O g+ CO2 (g)
Where M is the metal and the exact composition of the metal hydrogen carbonate and metal carbonate is determined by the charge of the metal.
MCO3 s → MO s+ CO2 (g)
Where M is the metal and the exact composition of the oxide formed is determined by the metal charge.
In the case of single replacement reactions, it is the activity series of metals that will determine if the reaction will occur, and what the products will be. A simple mnemonic will aid in useful in using the activity series. This mnemonic is, “the metal before replaces the ion after”. By using the following activity series, along with this mnemonic, the products are easily determined. The activity series is as follows
Activity Series of Metals
Li > K > Sr > Ca > Na > Mg >
Al > Zn > Cr > Fe > Cd > Co > Ni > Sn > Pb >
(H) > Cu > Hg > Ag > Pt > Au
This activity series is in order of most reactive to least reactive, with lithium being the most and gold being the least reactive. Hydrogen, written as (H), marks the transition between those metals that do react with acids (those before it), and those that do not (those after it). To use the mnemonic, think of dropping a chunk of that metal into a solution containing the other metal ion. For instance, dropping a copper wire into a solution of silver nitrate reveals that since the copper metal is “before” the silver ion, it will replace the silver in solution and the silver will deposit out in its normal state (solid in this case). If, however, a chunk of silver were put into a copper nitrate solution, no reaction would take place since the silver is not “before” the copper in the activity series.
One last distinction about the order of the activity series you may notice is that the top row comes all from Groups 1 and 2 on the periodic table, the middle row is comprised of the transition metals, and the bottom row are the “noble metals”, those that do not react with acids.
For the double replacement reactions, there is a method for determining which of the products is the precipitate. These guidelines are referred to as solubility rules. Follow the guidelines below, in order, to determine which of the products will be soluble, and which will be the precipitate.
Rules for Determining Solubility
1) All Li+, Na+, K+, NH4+ are Soluble
2) All NO3-, C2H3O2-, and ClO4- are Soluble
3) All Ag+, Hg2+, Pb2+, and Pb4+ are Insoluble
4) All Cl-, Br-, and I- are Soluble
5) All OH-, S2-, O2-, and CO32- are Insoluble
6) All SO42- are Soluble (except Ca2+ and Ba2+)
7) If not found here, assume Insoluble
Experiment 6 – Types of Reactions Name __________________
Lab Section __________________
Finally, it should be noted that by merely looking at the written equation, the evidence of the chemical reaction can usually be seen. There are four evidences of a chemical change. That is to say, if you see one, or more, of these, it indicates that a reaction has taken place. These four evidences are: permanent color change, gas released (g), precipitate (s), and heat/light being produced or absorbed. Look for these evidences throughout this lab.
Experiment 6 – Types of Reactions Name __________________
Lab Section __________________
Experiment 6 – Types of Reactions Name __________________
Lab Section __________________
Procedure
Experiment 6 – Types of Reactions Name __________________
Lab Section __________________
Combination Reaction: Instructor Demonstration
Magnesium burning in air
Sulfur burning in air
Decomposition Reaction:
CuSO4: Place a pea sized portion of copper (II) sulfate, CuSO4∙5H2O, into a large test tube. Using a test tube holder, gently heat the test tube over a Bunsen burner. Note any changes you see in the powder and the test tube. See Figure 6.1.
NaHCO3: Place enough sodium hydrogen carbonate (baking soda), NaHCO3, to lightly cover the bottom of an Erlenmeyer flask. Place the flask on a ring stand with wire gauze to support the flask on an iron ring.
With no flame under the flask, hold a burning splint directly on top of the mouth of the Erlenmeyer flask. Note how long the splint will burn. See Figure 6.2.
Heat the flask with the Bunsen burner and wait until moisture is observed at the mouth of the flask. Hold a burning splint above the mouth of the flask and observe how long the splint will burn.
Experiment 6 – Types of Reactions Name __________________
Lab Section __________________
Figure 6.1: Heating of CuSO4
Figure 6.2: Baking Soda Decomposition
Experiment 6 – Types of Reactions Name __________________
Lab Section __________________
Single Replacement: Leave all test tubes in the rack while doing these experiments
Put 20-30 drops of hydrochloric acid, HCl, into a small test tube. Add a piece of magnesium metal to the acid and note any changes that occur.
Put ~2 mL of water into a small test tube. Add a piece of calcium metal to the water and note any changes that occur.
Place 20-30 drops of silver nitrate, AgNO3, into a small test tube. Place a piece of copper wire into the test tube. Set the test tube aside to allow time for the reaction to take place. Note any changes that occur.
Double Replacement:
Put 10 drops of potassium carbonate, K2CO3, into three separate test tubes. To the first test tube, add 10 drops of silver nitrate, AgNO3. To the second test tube, add 10 drops of copper (II) nitrate, Cu(NO3)2. To the third test tube, add 10 drops of aluminum nitrate, Al(NO3)3. Note any changes that occur.
Put 10 drops of sodium phosphate, Na3PO4, into three separate test tubes. To the first test tube, add 10 drops of silver nitrate, AgNO3. To the second test tube, add 10 drops of copper (II) nitrate, Cu(NO3)2. To the third test tube, add 10 drops of aluminum nitrate, Al(NO3)3. Note any changes that occur.
Neutralization:
Put 10 drops of nitric acid, HNO3, sulfuric acid, H2SO4, and phosphoric acid, H3PO4, into three separate test tubes. Add two drops of phenolphthalein to each of the test tubes. This will act as the indicator for this reaction. Add sodium hydroxide, NaOH, to each of the test tubes. Note how many drops it takes until a permanent color change is observed. You may have to gently shake the test tube to mix the solutions. Do NOT put your finger over the lip of the test tube and shake the solution. Your instructor will show you the proper way to mix solutions in test tubes.
Prelaboratory Questions
What do the symbols (s), (l), (g), and (aq) mean?
What are the four evidences of a chemical reaction?
Indicate which of the following reactions would occur? (use the activity series listed on page XXXXX)
Fe s + HCl(aq) →
K s +H2O (l) →
Au s + KNO3 (aq) →
Indicate which of the following is soluble in water? (use the solubility rules listed on page XXXXXX)
NaCl Fe(NO3)2 Fe2O3 CaO (NH4)3PO4
Experiment 6 – Types of Reactions Name __________________
Lab Section __________________
Data Table
Combination
Mgs + O2 (g) D
Ss + O2 (g) D
Decomposition
CuSO4·5H2O s D
NaHCO3s →
NaHCO3(s) D
Single Replacement
Mg s + HCl(aq) →
Ca s +H2O (l) →
Cu s + AgNO3 (aq) →
Double Replacement
K2CO3aq + AgNO3 aq →
K2CO3aq + Cu(NO3 )2aq →
K2CO3aq + Al(NO3)3aq →
Na3PO4aq + AgNO3 aq →
Na3PO4 aq + Cu(NO3 )2 aq →
Na3PO4 aq + Al(NO3)3 aq →
Neutralization
HNO3 aq + NaOH aq →
H2SO4 aq + NaOH aq →
H3PO4 aq + NaOH aq →
Observation
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Experiment 6 – Types of Reactions Name __________________
Lab Section __________________
Postlaboratory Questions
Complete and balance the following reactions
Combination
magnesium + oxygen → magnesium oxide (s)
____Mgs + ____ O2 (g) D
sulfur + oxygen → sulfur dioxide (g)
____Ss + ____ O2 (g) D
Decomposition
copper sulfate pentahydrate → copper sulfate (s) + water (g)
____CuSO4·_5_H2O s D
sodium hydrogen carbonate → sodium carbonate (s) + carbon dioxide (g) + water (g)
____NaHCO3s →
Single Replacement
magnesium + hydrochloric acid → magnesium chloride (aq) + hydrogen (g)
____Mg s + ____HCl(aq) →
calcium + water → calcium hydroxide (s) + hydrogen (g)
____Ca s +____H2O (l) →
copper + silver nitrate → copper (II) nitrate (aq) + silver (s)
____Cu s + ____AgNO3 aq →
Double Replacement
silver nitrate (aq) + potassium carbonate (aq) → silver carbonate (s) + potassium nitrate (aq)
____ AgNO3 aq +____ K2CO3aq →
copper (II) nitrate (aq) + potassium carbonate (aq) → copper (II) carbonate (s) + potassium nitrate (aq)
____Cu(NO3 )2aq +____ K2CO3aq →
aluminum nitrate (aq) + potassium carbonate (aq) → aluminum carbonate (s) + potassium nitrate (aq)
____Al(NO3)3aq +____ K2CO3aq →
silver nitrate (aq) + sodium phosphate (aq) → silver phosphate (s) + sodium nitrate (aq)
____ AgNO3 aq +____ Na3PO4aq →
copper (II) nitrate (aq) + sodium phosphate (aq) → copper (II) phosphate (s) + sodium nitrate (aq)
____ Cu(NO3 )2 aq +____ Na3PO4 aq →
aluminum nitrate (aq) + sodium phosphate (aq) → aluminum phosphate (s) + sodium nitrate (aq)
____Al(NO3)3 aq +____ Na3PO4 aq →
Neutralization
nitric acid (aq) + sodium hydroxide (aq) → sodium nitrate (aq) + water (l)
____HNO3 aq + ____NaOH aq →
sulfuric acid (aq) + sodium hydroxide (aq) → sodium sulfate (aq) + water (l)
____H2SO4 aq + ____NaOH aq →
phosphoric acid (aq) + sodium hydroxide (aq) → sodium phosphate (aq) + water (l)
____H3PO4 aq +____ NaOH aq →
More reactions – Identify the type of reaction, predict the products, and balance.
____ Pb(NO3 )2aq +____KCl aq →
Type of reaction _______________
____Ca s+ ____S g →
Type of reaction _______________
____FeCl3 aq+ ____Mg s →
Type of reaction _______________
____Ca(HCO3)2 s D
Type of reaction _______________
____H3PO4aq+ ____Mg(OH)2 s →
Type of reaction _______________
Determine whether the following are soluble or insoluble: (circle the correct answers)
Experiment 6 – Types of Reactions Name __________________
Lab Section __________________
Experiment 6 – Types of Reactions Name __________________
Lab Section __________________
Pbl2
K3PO4
BaCr2O7
Mg(OH)2
CaCO3
Fe2S3
Experiment 6 – Types of Reactions Name __________________
Lab Section __________________
Experiment 6 – Types of Reactions Name __________________
Lab Section __________________
Na2SO4
TiO2
NH4OH
CoCl2
HC2H3O2
CaSO4
Experiment 6 – Types of Reactions Name __________________
Lab Section __________________
Which of the following metal/solution pairings would react? (circle the correct answers)
Experiment 6 – Types of Reactions Name __________________
Lab Section __________________
Mg with AgNO3
Fe with CaCl2
Pb with ZnCl2
Sn with HCl
Hg with K2SO4
Zn with AlCl3
Ca with PbNO3
Fe with H2O
Ni with BaCl2
K with LiC2H3O2
Au with H2SO4
Cr with MgF2