0.3 g of platinichloride of an organic diacidic base left 0.09 g of platinum on ignition. The molecular weight of the organic base is

Options

A. 120
B. 240
C. 180
D. 60

Explanation

To find the molecular weight of the organic diacidic base from the given information, we can follow these steps:

### Step 1: Determine the amount of platinichloride and platinum
We are given that 0.3 g of platinichloride (BH₂PtCl₆) yields 0.09 g of platinum upon ignition.

### Step 2: Calculate the molar mass of platinichloride
We know that the molar mass of platinum (Pt) is 195 g/mol. We can set up a proportion to find the molar mass of the platinichloride.

\[ \text{If } 0.09 \text{ g of Pt corresponds to } 0.3 \text{ g of platinichloride, then:} \]

\[ \frac{0.09 \text{ g Pt}}{195 \text{ g/mol}} = \frac{0.3 \text{ g platinichloride}}{M} \]

Where \( M \) is the molar mass of the platinichloride.

### Step 3: Solve for the molar mass of platinichloride
Cross-multiplying gives us:

\[ 0.09 \times M = 0.3 \times 195 \]

Calculating the right side:

\[ 0.3 \times 195 = 58.5 \]

Now we can solve for \( M \):

\[ M = \frac{58.5}{0.09} = 650 \text{ g/mol} \]

### Step 4: Calculate the molar mass of the organic base
The formula for the platinichloride is BH₂PtCl₆. We need to find the molar mass of the organic base (B).

The molar mass of PtCl₆ can be calculated as follows:

- Molar mass of Cl = 35.45 g/mol
- Molar mass of Cl₆ = 6 × 35.45 = 212.7 g/mol

Now, we can find the molar mass of PtCl₆:

\[ \text{Molar mass of PtCl₆} = 195 \text{ (Pt)} + 212.7 \text{ (Cl₆)} = 407.7 \text{ g/mol} \]

### Step 5: Calculate the molar mass of the organic base
Now we can find the molar mass of the organic base (B):

\[ \text{Molar mass of BH₂PtCl₆} = 650 \text{ g/mol} \]

Thus,

\[ \text{Molar mass of B} = 650 - 407.7 = 242.3 \text{ g/mol} \]

### Final Answer
The molecular weight of the organic diacidic base is approximately **242.3 g/mol**.

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