To solve the problem step by step, we will follow these calculations:
### Step 1: Determine the mass of oxygen in E₂O₃
We know that 8 g of E₂O₃ contains 5.6 g of element E. Therefore, we can find the mass of oxygen in the compound.
**Calculation:**
\[
\text{Mass of O} = \text{Total mass of E₂O₃} - \text{Mass of E} = 8 \, \text{g} - 5.6 \, \text{g} = 2.4 \, \text{g}
\]
### Step 2: Calculate the number of moles of oxygen
Next, we need to calculate the number of moles of oxygen (O) in 2.4 g. The molar mass of oxygen (O) is approximately 16 g/mol.
**Calculation:**
\[
\text{Moles of O} = \frac{\text{Mass of O}}{\text{Molar mass of O}} = \frac{2.4 \, \text{g}}{16 \, \text{g/mol}} = 0.15 \, \text{moles}
\]
### Step 3: Determine the moles of E in E₂O₃
In the formula E₂O₃, there are 2 moles of E for every 3 moles of O. Therefore, we can find the moles of E using the moles of O calculated in the previous step.
**Calculation:**
\[
\text{Moles of E} = \frac{2}{3} \times \text{Moles of O} = \frac{2}{3} \times 0.15 \, \text{moles} = 0.10 \, \text{moles}
\]
### Step 4: Find the number of moles of E in 16.8 g
Now, we need to determine how many moles of E are present in 16.8 g. We know that 5.6 g of E corresponds to 0.10 moles. We can set up a ratio to find the moles in 16.8 g.
**Calculation:**
\[
\text{Ratio} = \frac{16.8 \, \text{g}}{5.6 \, \text{g}} = 3
\]
Thus, the moles of E in 16.8 g will be:
\[
\text{Moles of E in 16.8 g} = 3 \times 0.10 \, \text{moles} = 0.30 \, \text{moles}
\]
### Final Answer:
The number of moles of E in 16.8 g is **0.30 moles**.
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