Reactions of Ions

Introduction:

Ionic compounds are made up of positively and negatively charged particles. In a water solution, these compounds dissociate, or break up into the ions of which they are made. For example, in water, solid sodium nitrate, NaNO3, breaks up into separate Na+and NO3- ions; sodium carbonate, Na2CO3, breaks up into Na +and CO32-ions; and calcium nitrate, Ca(NO3)2, breaks up into Ca 2+and NO3-ions. When two ionic compounds are present in dissociated form in the same solution, different compounds may form. For a different compound to form, a chemical reaction must occur. A change in the appearance of the solution indicates that a chemical reaction has taken place.

Problem:

How can you determine which ionic compound has formed in a solution containing known ions?

Materials:

graduated cylindertest tube rack4 test tubes

sodium nitrate solutiongrease pencilstoppers for test tube

sodium carbonate solutionwhite vinegarcalcium nitrate solution

4 droppers

Procedure:

Observations:

Solution / Observation of appearance
Sodium carbonate
Calcium nitrate
Sodium nitrate
Vinegar (acetic acid)
Reactants /

Observations

Sodium carbonate + calcium nitrate
Sodium nitrate + acetic acid
Acetic acid + contents of tube with sodium carbonate and calcium nitrate.

Analysis:

  1. a. What was the evidence that a chemical change occurred when the calcium

nitrate and sodium carbonate were mixed?

  1. Based on your answer and your knowledge of ions in solution, what are the possible compositions of the visible products that formed during this reaction?
  1. Based on your observation on what sodium nitrate looks like, what do you think was the actual product of this reaction?
  1. Based on your previous answer, what ions remained in solution?
  1. What do you think was formed when acetic acid was added to the test tube that contained the products of the calcium nitrate and sodium carbonate mixture? How did you come to this conclusion? Hint : Think about what happened when you mixed the acetic acid and the sodium nitrate solution to help you rule out possibilities.
  1. What do you think would happen if you mixed acetic acid and sodium carbonate?

Conclusion:

  1. Write a sentence or an equation to explain what happened when calcium nitrate was added to sodium carbonate.
  1. a. Do reactions involving ionic substances affect all the particles in solution,

or do some ions not react? Explain your answer.

  1. Why are some particles called spectator ions?
  1. Using the information from the lab, make a general statement about what can happen when solutions containing different ions are mixed.