`Ph-overset(O)overset(||)(C)-OH overset(overset(14)(NaHCO_(3)))rarr(A)` gas , `Ph-OH overset(Na)rarr(B)` gas
Sum of molecular mass of gas `(A+B = ?)`

Answer

To solve the problem, we need to analyze the two reactions given and identify the gases produced (A and B) and their respective molecular masses.

### Step 1: Identify the first reaction
The first reaction involves a carboxylic acid (Ph-COOH) reacting with sodium bicarbonate (NaHCO3).

**Reaction:**
\[ \text{Ph-COOH} + \text{NaHCO}_3 \rightarrow \text{Ph-COO}^- \text{Na}^+ + \text{H}_2\text{CO}_3 \]

Here, carbonic acid (H2CO3) decomposes into water (H2O) and carbon dioxide (CO2), which is a gas.

**Gas A:**
The gas produced here is CO2, which is derived from the decomposition of carbonic acid.

### Step 2: Calculate the molecular mass of gas A
Since the carbon in NaHCO3 is the carbon isotope C-14, the molecular mass of CO2 (gas A) can be calculated as follows:
- Carbon (C-14): 14 g/mol
- Oxygen (O): 16 g/mol (2 oxygen atoms contribute 32 g/mol)

**Molecular Mass of A:**
\[ 14 + 32 = 46 \text{ g/mol} \]

### Step 3: Identify the second reaction
The second reaction involves phenol (Ph-OH) reacting with sodium (Na).

**Reaction:**
\[ \text{Ph-OH} + \text{Na} \rightarrow \text{Ph-O}^- \text{Na}^+ + \text{H}_2 \]

Here, hydrogen gas (H2) is produced as a result of the reaction.

**Gas B:**
The gas produced in this reaction is H2.

### Step 4: Calculate the molecular mass of gas B
The molecular mass of H2 can be calculated as follows:
- Hydrogen (H): 1 g/mol (2 hydrogen atoms contribute 2 g/mol)

**Molecular Mass of B:**
\[ 2 \text{ g/mol} \]

### Step 5: Calculate the total molecular mass of gases A and B
Now, we can find the sum of the molecular masses of gases A and B:
\[ \text{Total Molecular Mass} = \text{Molecular Mass of A} + \text{Molecular Mass of B} \]
\[ = 46 + 2 = 48 \text{ g/mol} \]

### Final Answer
The sum of the molecular mass of gas A and gas B is **48 g/mol**.

---