# 6: Single and Double Displacement Reactions (Experiment)

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##### Objectives
• To perform and observe the results of a variety of single and double displacement reactions,
• To become familiar with some of the observable signs of these reactions,
• To identify the products formed in each of these reactions,
• To write balanced chemical equations for each single and double displacement reaction studied.

During a chemical reaction both the form and composition of matter are changed. Old substances are converted to new substances, which have unique physical and chemical properties of their own. Some of the observable signs that a chemical reaction has occurred include the following:

• A metallic deposit appears
• Bubbles appear
• A temperature change occurs
• A color change occurs
• A precipitate (cloudy, tiny particles) appears

Note that there are many other observable signs for chemical reactions, but these are the ones most likely to be encountered in this lab.

### Single Displacement Reactions

All single displacement reactions have the general form:

$A + BC → B + AC$

Here, $$A$$ is an element and $$BC$$ is usually an aqueous ionic compound or an acid (consisting of $$B^+$$ and $$C^-$$ aqueous ions). A displaces $$B$$ in $$BC$$, resulting in the formation of a new element $$B$$ and a new ionic compound or acid, $$AC$$. If the new element $$B$$is a metal, it will appear as a metallic deposit. If it is a gas, it will appear as bubbles.

An Activity Series of elements is often used to determine if $$A$$ will displace $$B$$ in a single displacement reaction. An Activity Series is provided at the end of the Background section. As a rule, if A has a higher activity that $$B$$, a single displacement reaction will occur. However, if $$A$$ has lower activity than $$B$$, a single displacement reaction will not occur.

##### Example 6.1 :

magnesium metal + aqueous aluminum chloride

Since $$\ce{Mg}$$ is more active than $$\ce{Al}$$, a single displacement reaction will occur. The predicted products are aluminum metal and aqueous magnesium chloride

Reaction Equation:

$\ce{3 Mg (s) + 2 AlCl3 (aq) -> 2 Al (s) + 3 MgCl2 (aq)}$

### Double Displacement Reactions

All double displacement reactions have the general form:

$AB + CD → AD + CB$

Reactions that can be classified as double displacements include precipitation reactions, neutralization reactions and gas forming reactions.

### Precipitation Reactions

Here $$AB$$ and $$CD$$ are usually aqueous ionic compounds (or acids) consisting of aqueous ions ($$A^+$$ and $$B^-$$, $$C^+$$ and $$D^-$$). When a double displacement reaction occurs, the cations and anions switch partners, resulting in the formation of two new ionic compounds AD and CB, one of which is in the solid state. This solid product is an insoluble ionic compound called a precipitate. To determine whether a product ionic compound will be soluble or insoluble, consult the Solubility Rules provided at the end of the Background section. Note that if both of the predicted products are soluble, a precipitation reaction will not occur.

##### Example 6.2 :

aqueous lead(II) nitrate + aqueous potassium chloride

The predicted products are lead(II) chloride (insoluble) and potassium nitrate (soluble).

Since one of the predicted products is insoluble, a precipitation reaction is will occur.

Reaction Equation:

$\ce{Pb(NO3)2 (aq) + 2 KCl (aq) -> 2 KNO3 (aq) + PbCl2 (s)}$

### Neutralization Reactions

Here $$AB$$ is an acid (consisting of $$H^+$$ and $$X^-$$ aqueous ions) and $$BC$$ is a base (consisting of $$M^+$$ and $$OH^-$$ ions). When a double displacement reaction occurs, the cations and anions switch partners, resulting in the formation of water and a new ionic compound (or salt), which is usually soluble. Neutralization reactions are exothermic, and are generally accompanied by a noticeable release of heat.

##### Example 6.3 :

sulfuric acid + aqueous lithium hydroxide

The predicted products are water and lithium sulfate.

Reaction Equation:

$\ce{H2SO4 (aq) + 2 LiOH (aq) -> Li2SO4 (aq) + 2 H2O (l)}$

### Gas Forming Reactions

In these reactions one of the products ($$AD$$ or $$CB$$) after the double displacement is in the gaseous state. One such example is hydrogen sulfide ($$\ce{H2S}$$). However, one of the products could also be carbonic acid ($$\ce{H2CO3}$$) or sulfurous acid ($$\ce{H2SO3}$$). Both carbonic acid and sulfurous acid are unstable and will decompose to form carbon dioxide and sulfur dioxide gases, respectively:

Carbonic acid:

$\ce{H2CO3 (aq) -> H2O (l) + CO2 (g)}$

Sulfurous Acid:

$\ce{H2SO3 (aq) -> H2O (l) + SO2 (g)}$

##### Example 6.4 :

nitric acid + aqueous sodium sulfite

The predicted products are sulfurous acid and sodium nitrate. However sulfurous acid decomposes to sulfur dioxide and water:

Reaction Equation:

$\ce{2 HNO3 (aq) + Na2SO3 (aq) -> 2 NaNO3 (aq) + H2SO3 (aq)} \text{(decomposes)}$

Final Equation:

$\ce{2 HNO3 (aq) + Na2SO3 (aq) -> 2 NaNO3 (aq) + H2O (l) + SO2 (g)}$

Writing Equations for Reactions

• Write the correct formulas for each reactant and place a yield arrow (→) after the last reactant.
• Identify the reaction type – single or double displacement, using the guidelines outlined thus far.
• If you determine that a reaction will occur, write the correct formula(s) of the products after the arrow. If you determine that a reaction will not occur, simply write “no reaction” after the arrow.
• Balance the equation (to ensure mass conservation).
• Be sure to include the physical states of all reactants and products in your final equation.

### Solubility Rules and Activity Series

Solubility Rules:

1. Alkali metal compounds, acetates, nitrates, and ammonium compounds are all soluble.
2. Hydroxides of alkali metals and $$\ce{NH4^{+1}}$$, $$\ce{Ca^{+2}}$$, $$\ce{Sr^{+2}}$$, and $$\ce{Ba^{+2}}$$ are soluble. All others are insoluble.
3. All halides (chlorides etc.) are soluble except for those containing $$\ce{Ag^{+1}}$$, $$\ce{Pb^{+2}}$$, and $$\ce{Hg2^{+2}}$$.
4. Most sulfates are soluble, except for $$\ce{BaSO4}$$, $$\ce{SrSO4}$$, $$\ce{Ag2SO4}$$, $$\ce{PbSO4}$$, and $$\ce{CaSO4}$$.
5. Most phosphates, carbonates, chromates and sulfides are insoluble (except those of the alkali metals and ammonium).
6. In addition, all acids are soluble!

Activity Series

 highest activity $$\ce{Li}$$ $$\ce{K}$$ $$\ce{Ca}$$ $$\ce{Na}$$ $$\ce{Mg}$$ $$\ce{Al}$$ $$\ce{Zn}$$ $$\ce{Cr -> Cr^{+3}}$$ $$\ce{Fe -> Fe^{+2}}$$ $$\ce{Cd}$$ $$\ce{Ni -> Ni^{+2}}$$ $$\ce{Sn -> Sn^{+2}}$$ $$\ce{Pb -> Pb^{+2}}$$ $$\ce{H2}$$ $$\ce{Cu -> Cu^{+2}}$$ $$\ce{Ag}$$ $$\ce{Hg -> Hg^{+2}}$$ lowest activity $$\ce{Au -> Au^{+3}}$$

## Procedure

Materials and Equipment

Solids: Copper metal, zinc metal, magnesium metal, solid sodium bicarbonate

Solutions: 6 M sodium hydroxide, 6 M hydrochloric acid, 6 M ammonium hydroxide, 5% acetic acid; all other solutions are 0.1 M and include silver nitrate, barium chloride, sodium sulfate, potassium chloride, lead(II) nitrate, iron(III) chloride, sodium carbonate, cobalt(II) nitrate, sodium phosphate, zinc nitrate, copper(II) sulfate, sodium chloride, potassium nitrate, nickel(II) nitrate.

Equipment: 6 large test tubes, 8 small test tubes, plastic test tube rack (or large beaker)

##### Safety

Be especially cautious when using the 6 M $$\ce{HCl}$$ and 6 M $$\ce{NaOH}$$ as they can burn your skin. Also be aware that skin discoloration will result from contact with $$\ce{AgNO3}$$. If you feel any tingling sensations or see any color changes on your skin, flush with water immediately for a minimum of 15 minutes. Inform your instructor of any chemical contact as soon as possible.

### Instructions for Performing Reactions

For the reactions involving solid reactants (#2, 4, 5, 7, 11, 13), use the large test tubes. For reactions involving solutions only, use small test tubes. Always use clean test tubes that have been rinsed with distilled water. The test tubes do not have to be dry.

Use approximately 3-mL quantities of all solutions. A good estimate is to use two full dropper squirts of each chemical.

For reactions involving metals, use just 1-2 pieces of each metal. Place the metal in the test tube first, and then add the solution. The metal should be completely immersed in the solution used.

Perform the following reactions and record your observations for each on the report form. Note that some reactions take longer than others. Thus, if results are not obtained immediately, give the reaction some time. All waste is to be disposed of in the plastic container in the hood!

1. Aqueous barium chloride + aqueous sodium sulfate
2. Zinc metal + hydrochloric acid
3. Aqueous sodium phosphate + aqueous copper(II) sulfate
4. Copper metal + aqueous silver nitrate
5. Solid sodium bicarbonate + acetic acid
6. Aqueous nickel(II) nitrate + aqueous sodium hydroxide
7. Copper metal + aqueous zinc nitrate
8. Aqueous potassium chloride + aqueous silver nitrate
9. Hydrochloric acid + aqueous sodium hydroxide
10. Aqueous sodium carbonate + aqueous cobalt(II) nitrate
11. Zinc metal + aqueous lead(II) nitrate
12. Aqueous sodium chloride + aqueous potassium nitrate
13. Magnesium metal + acetic acid
14. Aqueous iron(III) chloride + aqueous ammonium hydroxide

When finished, complete your lab report by writing the balanced equations for each reaction studied.

## Pre-laboratory Assignment: Single and Double Displacement Reactions

1. In this lab you will perform a variety of single and double displacement reactions. What are three observable signs that a chemical reaction has occurred?
1. What is the general equation of a single displacement reaction?
1. For each of the following sets of reactants, write the balanced equation for the single displacement reaction that occurs. If you determine that a reaction will not occur, write “NR”, and provide a brief explanation.
• Aluminum metal + aqueous nickel(II) nitrate
• Gold metal + hydrobromic acid
1. What is the general equation of a double displacement reaction?
1. For each of the following sets of reactants, write the balanced equation for the double displacement reaction that occurs. If you determine that a reaction will not occur, write “NR”, and provide a brief explanation.
• Aqueous zinc chloride + aqueous sodium chromate
• Aqueous lithium hydroxide + phosphoric acid
1. The equipment required for this lab is fairly simple - just 8 small test tubes and 6 large test tubes.
• Using the small test tubes you will mix two aqueous solutions together and observe whether or not a reaction occurs. What quantity of each solution will you use? How will you estimate this quantity?
• What do the reactions studied in the large test tubes all have in common?
• In the reactions involving both a solid and a solution as reactants, which do you place in the test tube first?

## Lab Report: Single and Double Displacement Reactions

For each of the reactions performed,

• predict the reaction type (single or double displacement)
• predict the names and states of the products formed
• write the balanced “molecular” equation, including all physical states.

1. Aqueous barium chloride + aqueous sodium sulfate

 Reaction Type: Observations: Product Names & States (if none, why not?): Balanced Equation:

2. Zinc metal + hydrochloric acid

 Reaction Type: Observations: Product Names & States (if none, why not?): Balanced Equation:

3. Aqueous sodium phosphate + aqueous copper(II) sulfate

 Reaction Type: Observations: Product Names & States (if none, why not?): Balanced Equation:

4. Copper metal + aqueous silver nitrate

 Reaction Type: Observations: Product Names & States (if none, why not?): Balanced Equation:

5. Solid sodium bicarbonate + acetic acid

 Reaction Type: Observations: Product Names & States (if none, why not?): Balanced Equation:

6. Aqueous nickel(II) nitrate + aqueous sodium hydroxide

 Reaction Type: Observations: Product Names & States (if none, why not?): Balanced Equation:

7. Copper metal + aqueous zinc nitrate

 Reaction Type: Observations: Product Names & States (if none, why not?): Balanced Equation:

8. Aqueous potassium chloride + aqueous silver nitrate

 Reaction Type: Observations: Product Names & States (if none, why not?): Balanced Equation:

9. Hydrochloric acid + aqueous sodium hydroxide

 Reaction Type: Observations: Product Names & States (if none, why not?): Balanced Equation:

10. Aqueous sodium carbonate + cobalt(II) nitrate

 Reaction Type: Observations: Product Names & States (if none, why not?): Balanced Equation:

11. Zinc metal + aqueous lead(II) nitrate

 Reaction Type: Observations: Product Names & States (if none, why not?): Balanced Equation:

12. Aqueous sodium chloride + aqueous potassium nitrate

 Reaction Type: Observations: Product Names & States (if none, why not?): Balanced Equation:

13. Magnesium metal + acetic acid

 Reaction Type: Observations: Product Names & States (if none, why not?): Balanced Equation:

14. Aqueous iron(III) chloride + aqueous ammonium hydroxide

 Reaction Type: Observations: Product Names & States (if none, why not?): Balanced Equation:

#### Questions

1. Consider Reactions 3 and 14 studied in this lab. Write the balanced molecular equation (identical to what you completed in the previous section), the complete ionic equation and the net ionic equation for these reactions. Include all physical states, and circle the spectator ions in the complete ionic equations.

Reaction 3: Aqueous sodium phosphate + aqueous copper(II) sulfate

• Balanced Molecular Equation (from page 1):
• Complete Ionic Equation:
• Net Ionic Equation:

Reaction 14: Aqueous iron(III) chloride + aqueous ammonium hydroxide

• Balanced Molecular Equation (from page 3):
• Complete Ionic Equation:
• Net Ionic Equation:
1. Predict the products for the following single and double displacement reactions, and write balanced molecular equations (including physical states) for each of them. If you predict that no reaction will occur, write “NR”, followed by a brief explanation.
• Aluminum metal + aqueous silver acetate
• Aqueous zinc nitrate + aqueous lithium chloride
• Hydrobromic acid + solid magnesium sulfite
• Aqueous rubidium hydroxide + perchloric acid
• Tin metal + phosphoric acid
• Aqueous lithium chromate + aqueous gold(III) iodide

6: Single and Double Displacement Reactions (Experiment) is shared under a CC BY-NC license and was authored, remixed, and/or curated by Santa Monica College.