February 26, 2014
Double Replacement Reactions
Abstract: In this lab the purpose was to observe different ionic solutions being mixed with other combinations and observe whiter a precipitate and note that a double replacement reaction was taking place.A double replacement reaction is when two different compounds react with each other. When this happens a cation and an anion break and form new bonds with other counterparts. This was accomplished and the results that were taken were accurate and precise. As expected there were some errors because the precipitate formed in some of the mixtures were hard to see but eventually they were found and noted.
Introduction: In this lab we will be doing double replacement reaction and example of such a reaction would be like the reaction of a antacid tablet that contains calcium carbonate that would them mix with the hydrochloric acid that is found in your stomach. To sum it up a double replacement reaction takes place between two ionic compounds that are dissolved in water where the cation in one compound replaces the cation in the other compound to create two new compounds. This new compound could be a precipitate, a gas, or water.
In this lab we will be mixing many pairs of aqueous solutions and ionic compounds together. From there we will observe what happens when each is mixed and see which form a precipitate. Then from there we will write balanced equations for each of the reactions.
Purpose: Is to find which combinations of ionic solutions form precipitates that indicate a double replacement reaction has taken place by mix different chemicals safely and seeing which ones from precipitates.
Procedure:After a well plate is obtained label the wells accordingly then using a micropipet place 5 drops of silver nitrate into wells A1-4. In wells B1—4 place 5 drops of iron nitrate solution and in wells C1-4 place 5 drops of copper (II) nitrate solution. Then add 5 drops of sodium phosphate solution into wells A B and C 1 then record what you saw. In wells A B and C 2 add 5 drops of sodium sulfate solutions then record those observations. Then in wells A B and C 3 place 5 drops of sodium hydroxide solution and again record observations. In the wells A B C C3 and C 4 place 5 drops sodium chloride solution and record what you see. Finally using a dropper pull the waste out the solutions in the A wells and dispose of them in a container provided by the teacher.
Results:1 / 2 / 3 / 4
Solutions / Na+₃-
PO₄ / Na+
SO₄2- / Na+
OH- / Na+
A / Ag+
NO₃- / Yes, formed a Yellow precipitate / None / Yes, formed a Brown precipitate / Yes, formed a Cloudy-Milky precipitate
B / Feᶟ⁺
NO₃ ‾ / Yes, formed a white precipitate / None / Yes, formed a orange precipitate / None
C / Cu^2+
NO₃ - / Yes, formed a Cloudy / Milky precipitate / None / None / None
A1: Na3PO4(aq) + 3AgNO3(aq) 3NaNO3(aq) +Ag3PO4(s)
A2: No Reaction
A3: AgNO3(aq) + NaOH(aq) AgOH(s) + NaNO3(aq)
A4: AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq)
B1: Fe(NO3)3(aq) + Na3PO4(aq) FePO4(s) + 3NaNO3(aq)
B2: No Reaction
B3: Fe(NO3)3(aq) + 3NaOH(aq) FeOH3(s) + 3NaNO3(aq)
B4: No Reaction
C1: AgNO3(aq) + NaCl(aq) AgCl(s) + NaNO3(aq)
C2: No Reaction
C3: No Reaction
C4: No Reaction
Conclusion: In this lab different ionic solutions were combined the see which combinations formed precipitates. These precipitate showed that a double replacement reaction was taking place. We mixed Sliver Nitrate with Sodium Phosphate, sodium sulfate, sodium hydroxide, and lastly we mixed the silver nitrate with sodium chloride. Then the steps were repeated but instead of using the silver nitrate, iron (III) nitrate was used in one and in the other Copper (II) nitrate was used. The results were as expected. The results that were produced were accurate and somewhat precise. The purpose of this experiment was accomplished. They were accomplished because the participants in this experiment now have a better understanding of double replacement reactions. They also have a better understanding of how to write and balance these types of chemical reactions.
Discussion: Some of the possible sources of error in the group might be that there was a precipitate formed but all the group saw was a color changed and didn’t think that was really a precipitate. This would have been a problem because a lot of the precipitate that were formed was really shown by drastic color changes. For C-3 I got the wrong result due to a contaminated experiment due water or an unknown in the micropipette because it was not cleaned well enough. For the most part the group had accurate and precise results. The main trouble point that caused the most error was the Sodium chloride; reason being is that the precipitate formed was very difficult to tell it just turned a bit cloudy. This could have been because not enough solution was mixed, it might have been contaminated, or it might have just supposed to be that way.
Over all the group’s results came out so that there was a precipitate when there was supposed a double replacement reaction happening and nothing happened when there was no precipitate showing that there wasn’t a double replacement reaction going on.