Experiment 6 - Activity Series: Single Replacement Reactions PDF

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When two aqueous solutions of ionic compounds react to form a new ionic substance that is not soluble in water, the presence of a solid (or a precipitate) is observed in the mixture. This type of reaction is called a precipitation reaction. A metathesis reaction is a reaction between compounds tha...

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Experiment 6: Activity Series: Single Replacement Reactions Required reading: Ebbing, 11th Edition Chapter 4. -Molecular and Ionic equations -Displacement reactions -Balancing redox equations Learning Goals:  To observe reactions of metals with acids and salt solutions using activity series of metals.  To be able to write and balance single replacement reactions using activity series of metals.  To be able to write ionic and net ionic equations for the above reactions. Background information and theory: One of the most important characteristics of a metal is its activity (reactivity). The activity of a metal is its ability to react with nonmetals. In such reaction, a metal typically loses electrons to the nonmetal to form cations and the product is an ionic compound. Different metals have different activity. Some metals are very active such as lithium, sodium, potassium, and cesium; some are slowly active such as tin, lead, and iron; and some are not active at all (inactive) such as copper, silver, and mercury. Inactive metals are those which resist oxidation. These are often called the noble metals. An activity series is the ranking of metals according to their reactivity. In an activity series metals are arranged in order of decreasing ability to lose electrons. Generally, the more reactive metals are placed at the left of the list. Li >K >Ba >Ca >Na >Mg >Al >Mn >Zn >Cr >Fe >Co >Ni >Sn >Pb > H >Cu >Ag >Hg >Pt >Au

More active

less active

Any metal before hydrogen will displace hydrogen gas, H2(g), from an acid, and any metal after hydrogen will not displace hydrogen from an acid. For example: Active metals (left to H) ; Inactive metals (right to H) ;

Zn (s) + 2HCl (aq)  ZnCl2 (aq) + H2 (g) Cu (s) + HCl (aq)  no reaction (NR)

In performing this experiment, you will observe and compare the reaction of some common metals with acids and salt solutions and establish an order of reactivity, from most active to least active. Reactivity of metals with HCl Very active metals will react with strong acids such as hydrochloric acid. An example considers magnesium: Molecular equation:

Mg (s) + 2HCl (aq)  MgCl2 (aq) + H2 (g)

Ionic equation: Mg (s) + 2H +(aq) + 2 Cl- (aq)  Mg 2+ (aq) + 2 Cl- (aq) + H2 (g) Net-ionic equation Mg (s) + 2H +(aq)  Mg 2+ (aq) + H2 (g) Note: Very active metals react vigorously and even explosively in acid. Thus Li, K, and Na should not be tested with hydrochloric acid.

Somewhat less reactive metals will slowly react with a strong acid such as hydrochloric acid. An example considers aluminum: Molecular equation: 2Al (s) + 6HCl (aq)  2AlCl3 (aq) + 3H2 (g) Ionic equation: 2Al (s) + 6 H+ (aq) + 6 Cl -(aq)  2 Al 3+(aq) + 3 Cl -(aq) + 3H2 (g) Net-ionic equation: 2Al (s) + 6 H+ (aq)  2 Al 3+(aq) + 3H2 (g) Reactivity of metal with aqueous salt solution The reaction of metals with a solution of salts of another metal is also revealing. The relative activities of the less active metals can be determined by observing reactions in which a more reactive metal (higher activity), such as magnesium, Mg, displaces ions of a less reactive metal, such as iron sulfate, FeSO 4, as a typical metallic salt or aqueous solutions. Molecular equation: Ionic equation: Net-ionic equation:

Mg (s) + FeSO4 (aq)  MgSO4 (aq) + Fe (s) 2+ 22+ 2Mg (s) + Fe (aq) + SO4 (aq)  Mg (aq) + SO4 (aq) + Fe (s) + Fe (s) Mg (s) + Fe2+(aq)  Mg2+(aq)

In this example, magnesium is said to be more active than iron because in the activity series magnesium is to the left of iron. The reverse of the reaction will not occur because Fe is less reactive and cannot displace ions of a more reactive metal, such as magnesium sulfate, MgSO4, as aqueous solution. Fe (s) + MgSO4 (aq)  N.R.

or

Fe (s) + Mg2+ (aq)  N.R.

Because a solution of many metal ions is colorless, often we must examine the reaction of a mixture carefully to establish whether or not a reaction has occurred. Changes in the appearance of the metal, a solution-color change, or the formation of precipitate all indicate that a reaction of this type has occurred. Sometimes, because metallic salt solutions are acidic, hydrogen gas, H2, is produced when the metal is added. In such cases, the formation of hydrogen gas, does not indicate a reaction between the metal and the salt solution. The fact that a metal does or does not react with a solution of another metallic salt can be used to establish the comparative reactivity of several metals. In this experiment, you will examine relative activities of common metals and compare your initial and final observations of the metals and the solutions. Based on these observations, you will determine whether or not a reaction has occurred, and, if so, with what intensity, slowly or rapidly. Using these results, you will arrange the metals in decreasing or increasing order of reactivity.

Procedure: Part I. Predictions With the help of the activity series provided in the background PREDICT whether the reactions you are about to perform will work or not. Write your prediction in your tables. Part II. Reactivity of metals with hydrochloric acid Watch the video: https://www.youtube.com/watch?v=Na_6j9y9ke8 1) In the video it is observed how a small piece of each metal, such as Ca, Mg, Fe, Cu, Zn, Sn is placed into labeled test tubes. 2) HCl is added into each metal sample in the test tubes. 3) Watch for evidence of the reaction by noting evolution of gas bubbles (Hydrogen gas) and any changes in the color or size of the metal. 4) Record your observations on the data table 1. Based on these observations, you will determine whether or not a reaction has occurred, and, if so, with what intensity, slowly or rapidly. 5) Write balanced equations for all occurred reactions on table 1. Part III. Reactivity of metal with aqueous salt solutions Watch the video: https://www.youtube.com/watch?v=gGJmY1KC94I 1) In the video it is observed how a small piece of each metal, such as Ca, Cu, Fe, Mg, Sn,, Zn is added to test tubes. 2) Aqueous solution of Ca(C2H3O2)2, MgSO4, CuSO4, Fe(NO3)3, Zn(NO3)2, and SnCl4 are added to each metal sample in the test tubes. 3) Watch for evidence of the reaction by noting changes in the color or size of the metal. 4) Record your observations on the data table 2. Based on these observations, you will determine whether or not a reaction has occurred, and, if so, with what intensity, slowly or rapidly. 5) Write balanced equations for all occurred reactions on data Table 3. Part IV. Verify your predictions Verify that your results correspond to the predicted results. If that is not the case, observe the reactions that didn’t work as expected or revise your prediction. Keep in mind that some of these reactions are very slow. Part V. Building an activity series 1) On data table 3, write complete and net equations for all those reactions that were supposed to work in parts 2 AND 3. All the spaces on table 3 must be completed. 2) Build an activity series for the 6 metals used.

Name: Daniela Almendarez Activity Series Data Data Table 1: Reactivity of metals with Hydrochloric Acid, HCl Metals Would Observation it Reactions (molecular, ionic, net-ionic) with HCl work? Yes Ca

It made a lot Molecular equation: Ca(s) + 2HCl(aq)  H2(g) + CaCl2(aq) of bubbles Ionic equation: Ca(s) + 2H+(aq) + 2Cl-(aq)  H2(g) + Ca2+(aq) + 2Cl-(aq) rapidly Net-ionic equation: Ca(s) + 2H+(aq) +  H2(g) + CaCl2(aq)

Yes Mg

No

The piece of Molecular equation: Mg(s) + 2HCl(aq)  H2(g) + MgCl2(aq) metal slowly was Ionic equation: Mg(s) + 2H+(aq) + 2Cl-(aq)  H2(g) + Mg2+(aq) + 2Cl(aq) decayed No reaction

Net-ionic equation: Mg(s) + 2H+(aq) +  H2(g) + MgCl2(aq) Molecular equation: Fe(s) + 2HCl(aq)  Fe(s) + 2HCl(aq) Ionic equation: Fe(s) + 2H+(aq) + 2Cl-(aq)  2H(aq) + Fe2+(s) + 2Cl-(aq)

Fe

Net-ionic equation: no reaction No

No reaction Molecular equation: Cu(s) + 2HCl(aq)  Cu(s) + 2HCl(aq) occurred Ionic equation: Cu(s) + 2H+(aq) + 2Cl-(aq)  2H(aq) + Cu2+(s) + 2Cl-

Cu

(aq)

Net-ionic equation: no reaction Yes Zn

The metal Molecular equation: Zn(s) + 2HCl(aq)  H2(g) + ZnCl2(aq) inflated Ionic equation: Zn(s) + 2H+(aq) + 2Cl-(aq)  H2(g) + Ca2+(s) + 2Cl-(aq) slowly Net-ionic equation: Zn(s) + 2H+(aq) +  H2(g) + ZnCl2(aq)

No Sn

No reaction

Molecular equation: Sn(s) + 2HCl(aq)  H2(g) + SnCl2(s) Ionic equation: Sn(s) + 2H+(aq) + 2Cl-(aq)  H2(g) + Sn2+(aq) + 2Cl-(aq)

Net-ionic equation: no reaction

Data Table 2: Observations of Reactivity of metals with metallic salt solutions Indicate your prediction by placing a checkmark on the corner of each box for those reactions that you think will work. Write your observations inside each box. Boxes in gray should remain empty as these reactions are not presented. Metals

Ca2+ as Mg 2+ as Fe3+ as Cu2+ as Zn2+ as Sn 4+ Ca(C2H3O2)2 MgSO4 Fe(NO3)3 CuSO4 Zn(NO3)2 SnCl4 Reaction

as

Reaction

Reaction

Reaction

Reaction

Displaces Fe from the solution and forms Mg(NO3)2

Displaces Cu from the solution and forms Mg(NO3)2

Displaces Zn from the solution and forms Mg(NO3)2

Reaction

Ca

No reaction

Mg

No reaction

No reaction

No reaction

No reaction

No reaction

No reaction

No reaction

No reaction

Displaces Cu from the solution and forms Fe(NO3)2

Fe

Cu

Zn

Sn

No reaction

No reaction

No reaction

Displaces Fe from the solution and forms Zn(NO3)2

Displaces Cu from the solution and forms Zn(NO3)2

Reaction

Reaction

Reaction

No reaction

Reaction

Reaction

Data Table 3: Reactions and activity seriesUse all the spaces provided using the reaction that actually worked on data table 1 and 2.

Complete equation Example: Ca(s) + 2HCl(aq)  H2(g) + CaCl2(aq)

Net ionic equation Ca(s) + 2H+(aq) +  H2(g) + Ca2+(aq)

Most reactive 1. ____Ca_ 2. __Mg___

3. __Zn___

4. _Fe____

Least reactive 5. __Sn___ 6. ___Cu__

Name: Daniela Almendarez Activity Series Postlab questions: Your instructor may ask you to answer these in your lab notebook, or to answer directly on this page and turn it in, or to include these answers in a formal lab report. Follow your instructor’s directions. 1. Balance the following reactions and indicate if they will occur (use activity series). a) Co + HCl  Co + 2HCl 

CoCl2 + H2

b) Hg + HCl 

CoCl2 + H2

c) Zn + Ni(NO3)3  Zn(NO3)2 +

Hg + 2HCl  Ni

HgCl2 + HgCl2 +

d) Li + HCl 

LiCl +

H2 H2 H2

2. What observations would you look for to determine if a metal undergoes reaction?

3. For each of the following reactions, identify; a. oxidized species b. reduced species c. oxidizing agent

I) 2 Fe (s) +

3 Cl2 (g)

II) Mg (s)

2 H2SO4 (aq) 

+



d. reducing agent

2 FeCl3(s)

MgSO4 (aq) +

SO2 (g) +

2 H2O (l)...