Select correct statement (s) :

Options

A. Acidic strength of `HBrgtHCl` but reverse is true for their reducing property
B. Basic strength of `PH_(3)gtAsH_(3)` but reverse is true for their bond angle
C. Dipole moment of `CH_(3)ClgtCH_(3)F ` but reverse is true for their `Hhat(C)H` bond angle
D. `K_(a_(1))` of fumaric acid is higher than maleic acid but reverse is true for their `K_(a_(2))`

Explanation

To solve the question of selecting the correct statement from the given options, we will analyze each option step by step.

### Step 1: Analyze Option A
**Statement:** The acidic strength of HBr is higher than HCl, but the reverse is true for their reducing property.

- **Acidic Strength:** HBr is indeed a stronger acid than HCl because bromine is a larger atom, allowing it to stabilize the negative charge better after losing a proton.
- **Reducing Property:** HBr is a better reducing agent than HCl because bromine is less electronegative than chlorine. Therefore, HBr can donate electrons more readily than HCl.

**Conclusion:** The first part of the statement is correct, but the second part is incorrect. Thus, Option A is **incorrect**.

### Step 2: Analyze Option B
**Statement:** The basic strength of PH3 is higher than ASH3, but the reverse is true for their bond angle.

- **Basic Strength:** PH3 is a weaker base than ASH3 because arsenic is larger and can better accommodate the lone pair of electrons, making it more available for bonding with protons.
- **Bond Angle:** The bond angle in PH3 is approximately 93.6°, while in ASH3 it is about 91.8°. Therefore, PH3 has a larger bond angle.

**Conclusion:** Both parts of the statement are incorrect. Thus, Option B is **incorrect**.

### Step 3: Analyze Option C
**Statement:** The dipole moment of CH3Cl is higher than CH3F, but the reverse is true for their HCH bond angle.

- **Dipole Moment:** CH3Cl has a higher dipole moment than CH3F because chlorine is less electronegative than fluorine, leading to a stronger overall dipole in CH3Cl.
- **HCH Bond Angle:** The bond angle in CH3F is larger than in CH3Cl due to the higher s-character in the C-F bond compared to the C-Cl bond.

**Conclusion:** Both parts of the statement are correct. Thus, Option C is **correct**.

### Step 4: Analyze Option D
**Statement:** Ka1 of fumaric acid is higher than malic acid, but the reverse is true for Ka2.

- **Ka1 Comparison:** Malic acid has a higher Ka1 than fumaric acid because malic acid is more stable after losing a proton.
- **Ka2 Comparison:** The statement claims the reverse for Ka2, which is also incorrect.

**Conclusion:** Both parts of the statement are incorrect. Thus, Option D is **incorrect**.

### Final Conclusion
The only correct statement is found in **Option C**: "The dipole moment of CH3Cl is higher than CH3F, but the reverse is true for their HCH bond angle."

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