`X` is the number of hydrogen bonds that surround each `H_(2)O` molecule in `H_(2)O(s), Y` is a similar number `Y` in `HF (s)`. What is `(X+Y)`?

Explanation

To solve the problem, we need to determine the number of hydrogen bonds surrounding each water molecule in solid water (ice) and each hydrogen fluoride (HF) molecule in solid HF, and then find the sum of these two values.

### Step-by-step solution:

1. **Identify the structure of solid water (ice):**
- Solid water (ice) has a crystalline structure where each water molecule is tetrahedrally coordinated to four other water molecules.
- Each water molecule can form four hydrogen bonds due to its two hydrogen atoms and two lone pairs of electrons.

**Calculation:**
- Therefore, the number of hydrogen bonds (X) surrounding each H₂O molecule in ice is **4**.

2. **Identify the structure of solid hydrogen fluoride (HF):**
- Solid HF also forms hydrogen bonds, but the arrangement is different. Each HF molecule can form hydrogen bonds with neighboring HF molecules.
- Each HF molecule can form two hydrogen bonds: one with a neighboring HF molecule and another with a different neighboring HF molecule.

**Calculation:**
- Therefore, the number of hydrogen bonds (Y) surrounding each HF molecule in solid HF is **2**.

3. **Calculate the sum of X and Y:**
- Now, we can find the total number of hydrogen bonds by adding the two values together:
\[ X + Y = 4 + 2 = 6 \]

### Final Answer:
The value of \(X + Y\) is **6**.

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