Incorrect statement is :

Options

A. `NaHCO_(3) and KHCO_(3)` have same crystal structure
B. On heating `LiNO_(3)` decomposes into `Li_(2)O an NO_(2)`
C. Among alkali metals, Li metal impart red colour flame
D. `Li_(2)SO_(4)` does not form alum

Explanation

To determine the incorrect statement among the given options, we will analyze each statement one by one.

### Step 1: Analyze the statement about NaHCO3 and KHCO3
- **Statement**: NaHCO3 and KHCO3 have the same crystal structure.
- **Analysis**: Sodium hydrogen carbonate (NaHCO3) forms a long chain structure, while potassium hydrogen carbonate (KHCO3) forms a dimer structure. Therefore, they do not have the same crystal structure.
- **Conclusion**: This statement is incorrect.

### Step 2: Analyze the statement about LiNO3 decomposition
- **Statement**: On heating, LiNO3 decomposes into Li2O and NO2.
- **Analysis**: The decomposition of lithium nitrate (LiNO3) on heating does indeed yield lithium oxide (Li2O), nitrogen dioxide (NO2), and oxygen (O2) as products. Thus, this statement is correct.
- **Conclusion**: This statement is correct.

### Step 3: Analyze the statement about alkali metals imparting red color flame
- **Statement**: Among alkali metals, lithium imparts a red color flame.
- **Analysis**: Lithium does impart a red color flame due to the excitation of its electrons. The electronic configuration of lithium allows for this color emission when heated. Therefore, this statement is correct.
- **Conclusion**: This statement is correct.

### Step 4: Analyze the statement about Li2SO4 and alum formation
- **Statement**: Li2SO4 does not form alum.
- **Analysis**: Lithium sulfate (Li2SO4) does not form alum because lithium has a very small ionic size, which prevents it from fitting into the structure of alum (double salts). Therefore, this statement is correct.
- **Conclusion**: This statement is correct.

### Final Conclusion
The only incorrect statement is that NaHCO3 and KHCO3 have the same crystal structure.

### Summary:
- **Incorrect Statement**: NaHCO3 and KHCO3 have the same crystal structure.

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