Chief ore of `Zn` is `ZnS`. The ore is concentrated by froth flotation process and then heated in air to convert `ZnS` to `ZnO`. ltntgt `2 ZnS + 3O_(2) rarr 2 ZnO + 2 SO_(2)`…(i)
`ZnO`, thus formed is treated with dilute `H_(2) SO_(4)`.
`ZnO + H_(2) SO_(4) rarr ZnSO_(4) + H_(2) O` ....(ii)
On electrolysis of `ZnSO_(4(aq)), Zn` metal is produced.
`2 ZnSO_(4) + H_(2) O rarr 2 Zn + 2H_(2) SO_(4) + O_(2)`....(iii)
What mass of `Zn` will be obtained from an ore containing `225 kg` of `ZnS` ? `(Zn = 65, S = 32, O = 16, H = 1)`.

Options

A. 102 kg
B. 151 kg
C. 112 kg
D. 134 kg

Explanation

To find the mass of zinc (Zn) that can be obtained from 225 kg of zinc sulfide (ZnS), we will follow these steps:

### Step 1: Write the reaction equations
The reactions involved in the extraction of zinc from zinc sulfide are as follows:

1. Conversion of ZnS to ZnO:
\[ 2 \text{ZnS} + 3 \text{O}_2 \rightarrow 2 \text{ZnO} + 2 \text{SO}_2 \]

2. Reaction of ZnO with dilute sulfuric acid (H₂SO₄):
\[ \text{ZnO} + \text{H}_2\text{SO}_4 \rightarrow \text{ZnSO}_4 + \text{H}_2\text{O} \]

3. Electrolysis of ZnSO₄ to produce zinc:
\[ 2 \text{ZnSO}_4 + \text{H}_2\text{O} \rightarrow 2 \text{Zn} + 2 \text{H}_2\text{SO}_4 + \text{O}_2 \]

### Step 2: Calculate the molar masses
- Molar mass of Zn = 65 g/mol
- Molar mass of S = 32 g/mol
- Molar mass of O = 16 g/mol

The molar mass of ZnS:
\[ \text{Molar mass of ZnS} = 65 + 32 = 97 \text{ g/mol} \]

### Step 3: Determine the number of moles of ZnS in 225 kg
Convert 225 kg to grams:
\[ 225 \text{ kg} = 225 \times 10^3 \text{ g} = 225000 \text{ g} \]

Now, calculate the number of moles of ZnS:
\[ \text{Moles of ZnS} = \frac{\text{mass of ZnS}}{\text{molar mass of ZnS}} = \frac{225000 \text{ g}}{97 \text{ g/mol}} \approx 2329.9 \text{ mol} \]

### Step 4: Use stoichiometry to find moles of Zn produced
From the reactions, we see that 2 moles of ZnS produce 2 moles of Zn. Therefore, the moles of Zn produced will be equal to the moles of ZnS:
\[ \text{Moles of Zn} = 2329.9 \text{ mol} \]

### Step 5: Calculate the mass of Zn produced
Now, calculate the mass of Zn produced using its molar mass:
\[ \text{Mass of Zn} = \text{moles of Zn} \times \text{molar mass of Zn} = 2329.9 \text{ mol} \times 65 \text{ g/mol} \approx 151000 \text{ g} \]

Convert grams to kilograms:
\[ \text{Mass of Zn} \approx 151 \text{ kg} \]

### Final Answer
The mass of zinc obtained from 225 kg of ZnS is approximately **151 kg**.

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