If Phosphonic acid, Tetrathionic acid and Pyrophosphoric acid
have number of acidic hydrogen per molecule respectively as
x,y and z, then find value of x+y-z

Explanation

To solve the problem, we need to determine the number of acidic hydrogens (x, y, z) in phosphonic acid, tetrathionic acid, and pyrophosphoric acid, respectively, and then calculate the expression \(x + y - z\).

### Step-by-Step Solution:

1. **Identify the Structure of Phosphonic Acid:**
- Phosphonic acid has the formula \(H_3PO_3\).
- The structure includes one phosphorus atom bonded to three hydrogens and two hydroxyl (OH) groups.
- The acidic hydrogens are those attached to the hydroxyl groups.
- Therefore, the number of acidic hydrogens (x) in phosphonic acid is **2** (from the two OH groups).

**Hint:** Count the number of OH groups in the structure to find the acidic hydrogens.

2. **Identify the Structure of Tetrathionic Acid:**
- Tetrathionic acid has the formula \(H_2S_4O_6\).
- The structure consists of four sulfur atoms and two hydroxyl (OH) groups.
- Similar to phosphonic acid, the acidic hydrogens are those attached to the hydroxyl groups.
- Therefore, the number of acidic hydrogens (y) in tetrathionic acid is **2** (from the two OH groups).

**Hint:** Look for the number of OH groups in the tetrathionic acid structure to determine the acidic hydrogens.

3. **Identify the Structure of Pyrophosphoric Acid:**
- Pyrophosphoric acid has the formula \(H_4P_2O_7\).
- The structure includes two phosphorus atoms and four hydroxyl (OH) groups.
- The acidic hydrogens are those attached to the hydroxyl groups.
- Therefore, the number of acidic hydrogens (z) in pyrophosphoric acid is **4** (from the four OH groups).

**Hint:** Count the number of OH groups in the pyrophosphoric acid structure to find the acidic hydrogens.

4. **Calculate the Expression \(x + y - z\):**
- We have determined:
- \(x = 2\) (from phosphonic acid)
- \(y = 2\) (from tetrathionic acid)
- \(z = 4\) (from pyrophosphoric acid)
- Now, substitute these values into the expression:
\[ x + y - z = 2 + 2 - 4 = 0 \]

**Final Answer:** The value of \(x + y - z\) is **0**.

### Summary of Values:
- \(x = 2\)
- \(y = 2\)
- \(z = 4\)
- \(x + y - z = 0\)