To analyze the statements given in the question, we will evaluate each statement one by one and determine their validity based on chemical principles.
### Step-by-Step Solution:
**Statement 1: Hydroxides of group-2 are less soluble in water than hydroxides of group-1.**
1. **Understanding Solubility:**
- The solubility of hydroxides in water is influenced by the balance between lattice energy and hydration energy.
- Lattice energy is the energy required to separate the ions in a solid ionic compound, while hydration energy is the energy released when ions are surrounded by water molecules.
2. **Group Comparison:**
- For Group 1 hydroxides (e.g., LiOH, NaOH, KOH), the lattice energy is relatively low compared to their hydration energy. This means they are generally soluble in water.
- For Group 2 hydroxides (e.g., Ca(OH)₂, Mg(OH)₂), the lattice energy is higher than that of Group 1 hydroxides and can be greater than the hydration energy, leading to lower solubility.
3. **Conclusion:**
- Therefore, Statement 1 is **True**: Hydroxides of group-2 are indeed less soluble in water than hydroxides of group-1.
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**Statement 2: CaF₂ is least soluble among other fluorides of group-2.**
1. **Analyzing Calcium Fluoride:**
- Calcium fluoride (CaF₂) has a high lattice energy due to the strong ionic bonds between Ca²⁺ and F⁻ ions.
- When compared to other group-2 fluorides (like MgF₂, SrF₂), CaF₂ is known to be less soluble in water.
2. **Comparison with Other Fluorides:**
- The solubility of fluorides generally decreases as the ionic size increases, and CaF₂ is less soluble than other group-2 fluorides due to its higher lattice energy.
3. **Conclusion:**
- Therefore, Statement 2 is **True**: CaF₂ is indeed the least soluble among the fluorides of group-2.
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**Statement 3: Li gives red colored flame.**
1. **Understanding Flame Colors:**
- The flame color produced by a metal ion when heated is due to the excitation of electrons. When these electrons return to their ground state, they emit light of specific wavelengths.
- Lithium (Li) is known to produce a red flame due to the emission of light at a wavelength corresponding to red color.
2. **Ionization Energy:**
- Lithium has a relatively low ionization energy, allowing its outermost electron to be easily excited to higher energy levels, and upon returning, it emits red light.
3. **Conclusion:**
- Therefore, Statement 3 is **True**: Lithium does give a red colored flame.
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### Final Conclusion:
All three statements are true. Therefore, the answer is **D**: All statements are true.
