1. State specifically how you would make a conclusive test for an iron (III) salt.
2. Which test for iron (II) ions is conclusive.
3. Suppose you have a solution containing both an iron (II) salt and an iron (III) salt. How would you proceed to identify both Fe2+ and Fe3+ in this solution?
If you could explain these questions/answers to me I would be very grateful. Thank you!
If you have the same lab as me read the introduction part of the lab... it has the answers for #1 and #2.... still stuck on #3 though
Sure, I'd be happy to help! Here are the step-by-step answers to your questions:
1. To make a conclusive test for an iron (III) salt, you can use the thiocyanate test. Follow these steps:
a. Take a small amount of the iron (III) salt solution in a test tube.
b. Add a few drops of potassium thiocyanate (KSCN) solution to the test tube.
c. Observe the color change in the solution.
d. If the solution turns reddish-brown, it indicates the presence of iron (III) ions.
2. The most conclusive test for iron (II) ions is the potassium hexacyanoferrate (II) test. Here's the step-by-step procedure:
a. Take a small amount of the iron (II) salt solution in a test tube.
b. Add a few drops of potassium hexacyanoferrate (II) solution (also known as potassium ferrocyanide, K4[Fe(CN)6]) to the test tube.
c. Observe any change in color.
d. If a deep blue precipitate (called Turnbull's blue) appears, it confirms the presence of iron (II) ions.
3. If you have a solution containing both an iron (II) salt and an iron (III) salt, you can follow these steps to identify both Fe2+ and Fe3+ ions:
a. Take a small amount of the solution in a test tube.
b. Add a few drops of potassium thiocyanate (KSCN) solution to the test tube.
c. If a reddish-brown color appears, it suggests the presence of iron (III) ions (Fe3+).
d. Now, add a few drops of potassium hexacyanoferrate (II) solution (potassium ferrocyanide) to the test tube.
e. If a deep blue precipitate (Turnbull's blue) forms, it confirms the presence of iron (II) ions (Fe2+).
By conducting these tests, you can conclusively identify the presence of iron (III) ions, iron (II) ions, or both in a given solution.
1. To make a conclusive test for an iron (III) salt, you can follow these steps:
Step 1: Add a few drops of a strong acid, such as hydrochloric acid, to the solution containing the iron (III) salt. This step is done to convert any iron (III) hydroxide or iron (III) oxide present into soluble iron (III) ions.
Step 2: To confirm the presence of iron (III) ions, you can perform a colorimetric test using potassium thiocyanate (KSCN) solution. This test is based on the formation of a blood-red complex between iron (III) ions and thiocyanate ions. Add a few drops of KSCN solution to the solution. If a blood-red color is observed, it confirms the presence of iron (III) ions.
Step 3: To further ensure that the iron (III) ions are present, you can perform a precipitation test. Add a few drops of sodium hydroxide (NaOH) solution to the original solution and observe for the formation of a brown precipitate. The brown precipitate is known as iron (III) hydroxide, confirming the presence of iron (III) ions.
2. The test for iron (II) ions that is considered conclusive is the Prussian blue test. To conduct this test, you can follow these steps:
Step 1: Add a few drops of hydrochloric acid (HCl) to the solution containing the iron (II) ions. This will ensure that any iron (II) hydroxide or iron (II) oxide present is converted into soluble iron (II) ions.
Step 2: Add a few drops of potassium ferricyanide (K3Fe(CN)6) solution to the solution. If iron (II) ions are present, a dark blue precipitate known as Prussian blue will form. The formation of Prussian blue confirms the presence of iron (II) ions.
3. To identify both Fe2+ and Fe3+ in a solution containing both an iron (II) salt and an iron (III) salt, you can use the following steps:
Step 1: Separate the Fe2+ and Fe3+ ions by adjusting the pH of the solution. Iron (II) ions are easily oxidized to iron (III) ions, so you need to oxidize all Fe2+ to Fe3+. To do this, add a few drops of a strong oxidizing agent, such as potassium permanganate (KMnO4), to the solution. The KMnO4 will convert all Fe2+ to Fe3+ ions.
Step 2: Once all the Fe2+ ions have been oxidized, adjust the pH of the solution to around 9-10, using a buffer solution or sodium hydroxide (NaOH). This will precipitate the iron (III) ions as iron (III) hydroxide while keeping the iron (II) ions in solution.
Step 3: Confirm the presence of Fe2+ ions in the solution by performing a test like the Prussian blue test mentioned earlier. If Prussian blue forms, it indicates the presence of Fe2+ ions.
Step 4: Confirm the presence of Fe3+ ions in the precipitate formed in Step 2 by performing a test like the potassium thiocyanate test mentioned earlier. The formation of a blood-red color indicates the presence of Fe3+ ions.
By following these steps, you can identify both Fe2+ and Fe3+ ions in the given solution containing both iron (II) and iron (III) salts.