Which of the following does not exist?

Options

A. `HS_(6)`
B. `HPO_(4)`
C. `FeI_(3)`
D. `HClO_(4)`

Explanation

To determine which of the given compounds does not exist, we will analyze each option based on their oxidation states and chemical feasibility.

### Step-by-Step Solution:

1. **Analyze Hs6**:
- Let the oxidation state of sulfur (S) be \( x \).
- The formula can be set up as follows:
\[ 6x + 1 = 0 \]
- Solving for \( x \):
\[ 6x = -1 \implies x = -\frac{1}{6} \]
- Since sulfur cannot have an oxidation state of \(-\frac{1}{6}\) (as oxidation states are typically whole numbers or simple fractions), Hs6 does not exist.

2. **Analyze HPO4**:
- HPO4 typically exists as HPO4^2- in ionic form, not as a neutral molecule.
- Therefore, the neutral form HPO4 does not exist.

3. **Analyze FeI3**:
- Let the oxidation state of iron (Fe) be \( x \).
- The equation for FeI3 is:
\[ x + 3(-1) = 0 \implies x - 3 = 0 \implies x = +3 \]
- An oxidation state of +3 for iron is possible, thus FeI3 exists.

4. **Analyze HClO4**:
- Let the oxidation state of chlorine (Cl) be \( x \).
- The equation for HClO4 is:
\[ x + 1 - 4(2) = 0 \implies x + 1 - 8 = 0 \implies x = +7 \]
- An oxidation state of +7 for chlorine is possible, thus HClO4 exists.

5. **Conclusion**:
- From the analysis, Hs6 and HPO4 do not exist, while FeI3 and HClO4 do exist.

### Final Answer:
The compounds that do not exist are **Hs6 and HPO4**.