Which of the following names is impossible ?

Options

A. Potassium tetrfluoridooxidochromate (VI)
B. Barium tetrafluoridochromate (II)
C. Dichlorobis (urea) copper (II)
D. All are impossible

Answer

To determine which of the given names is impossible, we will analyze each option based on the rules of nomenclature for coordination compounds.

### Step-by-Step Solution:

1. **Analyze the first option: Potassium tetrafluoride oxidochromate**
- The name indicates that we have potassium (K), tetrafluoride (F4), and oxidochromate.
- The chromate ion (CrO4) has a charge of -2.
- The overall charge of the coordination complex must balance with the potassium ion, which has a +1 charge.
- Let the oxidation state of chromium be \( x \).
- The equation for the charge balance is:
\[ x + 4(-1) + (-2) = -1 \]
Simplifying gives:
\[ x - 4 - 2 = -1 \implies x - 6 = -1 \implies x = +5 \]
- However, the name suggests that chromium is in the +6 oxidation state, which is inconsistent with our calculation. Thus, this name is impossible.

2. **Analyze the second option: Barium tetrafluoride chromate**
- Barium (Ba) has a +2 charge.
- The tetrafluoride indicates 4 F atoms, each with a -1 charge.
- The chromate ion (CrO4) has a -2 charge.
- Charge balance:
\[ +2 + 4(-1) + (-2) = 0 \]
Simplifying gives:
\[ 2 - 4 - 2 = 0 \]
- This is consistent, so this name is possible.

3. **Analyze the third option: Dichlorobis(urea)copper(II)**
- Urea (NH2CO) is a neutral bidentate ligand.
- Copper is in the +2 oxidation state as indicated.
- The two chloride ions (Cl) provide a -2 charge.
- Charge balance:
\[ +2 + 2(-1) = 0 \]
- This is also consistent, so this name is possible.

4. **Conclusion:**
- The only impossible name based on the analysis is **Potassium tetrafluoride oxidochromate** because the oxidation state of chromium does not match the expected value.

### Final Answer:
The impossible name is **Potassium tetrafluoride oxidochromate**.