CR_Single Displacement Reactions Lesson

Single Displacement Reactions 

image of couple dancing + one person dancingPredicting the products of single displacement reactions is much easier than predicting the products of synthesis or decomposition reactions. Just remember to replace a metal with a metal or a non-metal with a non-metal. And, as always, write the formulas of the products according to their charges.  

The only tricky part is predicting whether a reaction will actually occur or not! To do this, you will refer to something called an activity series (sometimes called an electrochemical series). An activity series arranges metals according to their ease of oxidation. Oxidation is a term you have not yet learned. We will discuss it later in the unit. For now, let's think of this more simply as chemical activity, as the name of the chart implies.

On this particular chart, the more active substances are listed at the bottom, but this is not always the case. Make sure to look at the orientation of the table before you use it.

Recall the general reaction. Metal A can replace metal B if it is a more active metal.

Metal Activity Series (Hydrogen is included for reference) Element Gold Mercury Silver Copper Hydrogen Lead Tin Cobalt Nickel Iron Chromium Zinc Manganese Aluminum Magnesium Sodium Calcium Strontium Barium Potassium Lithium Oxidation Product 3+ Au 2+ Hg + Ag 2+ Cu + H 2+ Pb 2+ Sn 2+ Co 2+ Ni 2+ Fe 3+ Cr 2+ Zn 2+ Mn 3+ Al 2+ Mg + Na 2+ Ca 2+ Sr 2+ Ba K Li Increasing Ease of Oxidation from top down -Increasing Metal Activity from top down

You may refer to an activity series in order to determine if these reactions occur or not. But, on the AP Exam, you will not have this document. There is another document that will be provided that will provide you the same information.   It is called a reduction potential table. You will learn about this in the electrochemistry unit. If you do not have access to either of these tables, you may be provided with some laboratory evidence that will allow you to develop your own table. Try this one on your own, and then watch the video to see if your thought process was correct!

Nonmetals participate in single displacement reactions as well. The only difference is that the nonmetal will be displaced instead of the metal. You would refer to a nonmetal activity series to determine if a reaction occurs or not.

Reactions with Water

Often, single displacement reactions occur between a metal and water. When you see these, the easiest way to predict and write the products is to first think of water as HOH instead of H2O. That way you can view the H+ as the cation and the OH- as the anion in order to make replacements in reactions. You will still need to refer to the activity series to determine if a reaction takes place or not.

Example #1 Let's look at the reaction of zinc with copper II sulfate solution. Zn(s) + CuSO4 (aq) → In order for a reaction to actually take place, zinc must be more active than copper. Look at the activity series to see that zinc is lower on this chart that copper, indicating that it is more active. So, a reaction does occur. Now all you have to do is switch the metals (rewriting the formulas). Zn(s) + CuSO4 (aq) → Cu(s) + ZnSO4 (aq) Example #2 Let's look at the reaction of tin and aqueous sodium chloride. Sn(s) + NaCl(aq) → In order for a reaction to actually take place, tin must be more active than sodium. Tin is higher on this chart that sodium, indicating that it is less active. So, a reaction does NOT occur. Write NR to indicate no reaction. Sn(s) + NaCl(aq)→→ NR

Whenever H2 gas is produced, it can easily be tested for by what is often called the hydrogen bark (or pop). If a flame is exposed to H2 gas, through a splint test, the hydrogen will burn and also make a barking type sound. You should keep a list of such characteristics of common chemicals that may help you identify them in situations or problems where their identity is unknown.

Remember to work on the module practice problems as you complete each section of content.

[CC BY-NC-SA 4.0 Links to an external site.] UNLESS OTHERWISE NOTED | IMAGES: LICENSED AND USED ACCORDING TO TERMS OF SUBSCRIPTION - INTENDED ONLY FOR USE WITHIN LESSON.