How many electrons per mole of Pt are transferred when aqua regia oxidized platinum?

Options

A. 3
B. 4
C. 5
D. 6

Explanation

To determine how many electrons per mole of platinum (Pt) are transferred when aqua regia oxidizes platinum, we can follow these steps:

### Step 1: Understand Aqua Regia
Aqua regia is a mixture of hydrochloric acid (HCl) and nitric acid (HNO₃). It is known for its ability to dissolve noble metals like platinum.

### Step 2: Write the Balanced Chemical Equation
The reaction between platinum and aqua regia can be represented as:
\[ \text{Pt} + \text{HNO}_3 + \text{HCl} \rightarrow \text{H}_2\text{PtCl}_6 + \text{NO} + \text{H}_2 \]

### Step 3: Balance the Chemical Equation
To balance the equation, we need to ensure that the number of atoms of each element is the same on both sides. The balanced equation is:
\[ 3 \text{Pt} + 18 \text{HCl} + 6 \text{HNO}_3 \rightarrow 6 \text{H}_2\text{PtCl}_6 + 6 \text{NO} + 6 \text{H}_2 \]

### Step 4: Determine the Total Moles of Electrons Transferred
From the balanced equation, we can see that for every 3 moles of platinum, a total of 12 moles of electrons are transferred. This is derived from the oxidation state changes in the reaction.

### Step 5: Calculate Electrons Transferred per Mole of Platinum
To find the number of electrons transferred per mole of platinum, we divide the total moles of electrons transferred by the number of moles of platinum:
\[ \text{Electrons per mole of Pt} = \frac{\text{Total moles of electrons}}{\text{Moles of Pt}} = \frac{12}{3} = 4 \]

### Final Answer
Thus, the number of electrons transferred per mole of platinum when oxidized by aqua regia is **4 electrons**.

---