How many of the following are saline hydrides?
`CH_(4),NaH, HF, CrH, PdH_(0.7), LiH, CaH_(2),TiH_(1.6)`

Answer

To determine how many of the given compounds are saline hydrides, let's first define what a saline hydride is. Saline hydrides are typically formed by the reaction of hydrogen with alkali metals (Group 1 elements) and alkaline earth metals (Group 2 elements). These hydrides are ionic in nature and usually have the general formula MH, where M is the metal.

Now, let's analyze each compound given in the question:

1. **CH₄ (Methane)**:
- This is a covalent compound formed between carbon and hydrogen. It is not a saline hydride.

2. **NaH (Sodium Hydride)**:
- Sodium is an alkali metal (Group 1). When it reacts with hydrogen, it forms NaH, which is a saline hydride.

3. **HF (Hydrofluoric Acid)**:
- This is a covalent compound formed between hydrogen and fluorine. It is not a saline hydride.

4. **CrH (Chromium Hydride)**:
- Chromium is a transition metal and does not belong to Group 1 or Group 2. Therefore, CrH is not a saline hydride.

5. **PdH₀.₇ (Palladium Hydride)**:
- Palladium is also a transition metal. Although it can form hydrides, it does not qualify as a saline hydride because it is not from Group 1 or Group 2.

6. **LiH (Lithium Hydride)**:
- Lithium is an alkali metal (Group 1). It forms LiH, which is a saline hydride.

7. **CaH₂ (Calcium Hydride)**:
- Calcium is an alkaline earth metal (Group 2). It forms CaH₂, which is also a saline hydride.

8. **TiH₁.₆ (Titanium Hydride)**:
- Titanium is a transition metal and does not belong to Group 1 or Group 2. Therefore, TiH₁.₆ is not a saline hydride.

Now, let's summarize the findings:

- Saline hydrides from the list:
- NaH (Sodium Hydride)
- LiH (Lithium Hydride)
- CaH₂ (Calcium Hydride)

Thus, the total number of saline hydrides in the provided list is **3**.

### Final Answer:
**3**