0.75 g platinic chloride, a monoacid base on ignition gave 0.245 g playinum. The molecular weight of the base is

Options

A. `75.0`
B. `93.5`
C. `100`
D. `80.0`

Explanation

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

### Step 1: Determine the amount of platinum in moles
Given that 0.245 g of platinum is produced, we first need to convert this mass into moles using the molar mass of platinum.

**Molar mass of platinum (Pt)** = 195 g/mol

\[ \text{Moles of Pt} = \frac{\text{mass of Pt}}{\text{molar mass of Pt}} = \frac{0.245 \, \text{g}}{195 \, \text{g/mol}} \approx 0.00126 \, \text{mol} \]

### Step 2: Relate moles of platinum to moles of the base
Since the base is a monoacid base, it will react with one mole of platinum for each mole of the base. Therefore, the moles of the base will also be equal to the moles of platinum produced.

\[ \text{Moles of base} = 0.00126 \, \text{mol} \]

### Step 3: Calculate the mass of the base
We know the mass of the platinic chloride (the compound containing the base) is 0.75 g. The mass of the base can be calculated using the stoichiometry of the reaction. The mass of the base can be calculated by subtracting the mass of platinum from the total mass of platinic chloride.

\[ \text{Mass of base} = \text{mass of platinic chloride} - \text{mass of platinum} = 0.75 \, \text{g} - 0.245 \, \text{g} = 0.505 \, \text{g} \]

### Step 4: Calculate the molar mass of the base
Now we can find the molar mass of the base using the formula:

\[ \text{Molar mass of base} = \frac{\text{mass of base}}{\text{moles of base}} = \frac{0.505 \, \text{g}}{0.00126 \, \text{mol}} \approx 400.79 \, \text{g/mol} \]

### Step 5: Conclusion
The molecular weight of the base is approximately 400.79 g/mol.

### Final Answer
The molecular weight of the base is approximately **400.79 g/mol**.

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