`NH_(4)SCN` can be used to test ion or more out of `Fe^(3+) ,Co^(2+),Cu^(2+)`

Options

A. `Fe^(3+) `only
B. `Co^(2+),Cu^(2+)`
C. `Fe^(2+),Cu^(2+)`
D. all

Answer

To determine which ions can be tested using ammonium thiocyanate (NH₄SCN), we will analyze the reactions of NH₄SCN with each of the given ions: Fe³⁺, Co²⁺, and Cu²⁺.

### Step-by-Step Solution:

1. **Testing for Fe³⁺ (Iron III ion)**:
- When ammonium thiocyanate reacts with iron (III) chloride (FeCl₃), it forms a blood-red complex known as iron(III) thiocyanate (Fe(SCN)₃).
- The reaction can be represented as:
\[ FeCl_3 + 3 NH_4SCN \rightarrow Fe(SCN)_3 + 3 NH_4Cl \]
- The formation of a blood-red color indicates the presence of Fe³⁺ ions.

2. **Testing for Co²⁺ (Cobalt II ion)**:
- When ammonium thiocyanate reacts with cobalt (II) chloride (CoCl₂), it forms a blue complex known as cobalt(II) thiocyanate (Co(SCN)₄²⁻).
- The reaction can be represented as:
\[ CoCl_2 + 4 NH_4SCN \rightarrow Co(SCN)_4 + 2 NH_4Cl \]
- The formation of a blue color indicates the presence of Co²⁺ ions.

3. **Testing for Cu²⁺ (Copper II ion)**:
- When ammonium thiocyanate reacts with copper (II) chloride (CuCl₂), it forms a black precipitate known as copper(I) thiocyanate (CuSCN).
- The reaction can be represented as:
\[ CuCl_2 + 2 NH_4SCN \rightarrow CuSCN + 2 NH_4Cl \]
- The formation of a black precipitate indicates the presence of Cu²⁺ ions.

### Conclusion:
Ammonium thiocyanate can be used to test for all three ions: Fe³⁺, Co²⁺, and Cu²⁺. Therefore, the answer is that NH₄SCN can be used to test for all of these ions.

### Final Answer:
All of these ions (Fe³⁺, Co²⁺, Cu²⁺) can be tested using NH₄SCN.

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