Which of the following statement(s) is/are not correct?

Options

A. Nickel salts give rosy red precipitate with dimethyl glyoxime in excess of `NH_(4)OH`
B. `Fe(III)` salts give red colour with potassium sulphocyanide
C. In nitroprusside the iron and `NO` exists as `Fe(III)` and `NO`
D. `Mn (II)` salts give white precipitate with `NaOH` which turns brown on adding `Br_(2)` water.

Explanation

To determine which of the statements provided is not correct, we will analyze each option step by step.

### Step 1: Analyze the first statement
**Statement 1:** Nickel salt gives rosy red precipitate with dimethylglyoxime in NH4OH.

- Nickel (Ni) in the +2 oxidation state reacts with dimethylglyoxime (DMG) in the presence of ammonium hydroxide (NH4OH).
- The reaction forms a complex, specifically Ni(DMG)2, which is known to produce a rosy red precipitate.

**Conclusion:** This statement is correct.

### Step 2: Analyze the second statement
**Statement 2:** Fe3+ salt gives red color with potassium thiocyanate.

- When iron (III) ions (Fe3+) react with potassium thiocyanate (KSCN), they form a complex known as iron(III) thiocyanate, represented as [Fe(SCN)]2+.
- This complex is indeed deep red in color.

**Conclusion:** This statement is also correct.

### Step 3: Analyze the third statement
**Statement 3:** In nitroprusside, the iron and NO exist as Fe3+ and NO.

- Nitroprusside is a complex with the formula [Fe(CN)5(NO)]2-.
- In this complex, iron is in the +2 oxidation state (Fe2+) and not in the +3 state (Fe3+). The NO is present as a ligand and does not exist as NO in the +3 state.

**Conclusion:** This statement is incorrect.

### Step 4: Analyze the fourth statement
**Statement 4:** Mn2+ salt gives white precipitate with NaOH which turns brown on adding Br2 water.

- When manganese (II) ions (Mn2+) react with sodium hydroxide (NaOH), they form manganese(II) hydroxide, Mn(OH)2, which is a white precipitate.
- Upon adding bromine water (Br2), Mn(OH)2 is oxidized to manganese(III) oxide hydroxide (MnOOH), which is brown in color.

**Conclusion:** This statement is correct.

### Final Conclusion
The statement that is not correct is **Statement 3**: "In nitroprusside, the iron and NO exist as Fe3+ and NO."

### Summary of Incorrect Statement:
- **Incorrect Statement:** Statement 3 is incorrect because in nitroprusside, iron is in the +2 oxidation state, not +3.