What mass of hydrogen and oxygen will be produced on complete electrolysis of 18 g of water?

Options

A. 2 g hydrogen and 32 g oxygen
B. 2 g hydrogen and 16 g oxygen
C. 4 g hydrogen and 32 g oxygen
D. 4 g hydrogen and 14 g oxygen

Explanation

To determine the mass of hydrogen and oxygen produced from the complete electrolysis of 18 grams of water, we can follow these steps:

### Step 1: Write the Electrolysis Reaction
The electrolysis of water (H₂O) can be represented by the following chemical equation:
\[ 2 H_2O \rightarrow 2 H_2 + O_2 \]
This indicates that 2 moles of water produce 2 moles of hydrogen gas and 1 mole of oxygen gas.

### Step 2: Calculate Molar Masses
Next, we need to calculate the molar masses of water, hydrogen, and oxygen:
- The molar mass of water (H₂O) = 2(1) + 16 = 18 g/mol
- The molar mass of hydrogen (H₂) = 2(1) = 2 g/mol
- The molar mass of oxygen (O₂) = 2(16) = 32 g/mol

### Step 3: Determine Moles of Water
Now, we can find out how many moles of water are present in 18 grams:
\[ \text{Moles of } H_2O = \frac{\text{mass}}{\text{molar mass}} = \frac{18 \text{ g}}{18 \text{ g/mol}} = 1 \text{ mole} \]

### Step 4: Use Stoichiometry to Find Moles of Hydrogen and Oxygen
From the balanced equation, we know:
- 2 moles of water produce 2 moles of hydrogen and 1 mole of oxygen.
Thus, 1 mole of water will produce:
- 1 mole of hydrogen (H₂)
- 0.5 moles of oxygen (O₂)

### Step 5: Convert Moles to Mass
Now, we convert the moles of hydrogen and oxygen back to grams:
- For hydrogen:
\[ \text{Mass of } H_2 = \text{moles} \times \text{molar mass} = 1 \text{ mole} \times 2 \text{ g/mol} = 2 \text{ g} \]
- For oxygen:
\[ \text{Mass of } O_2 = \text{moles} \times \text{molar mass} = 0.5 \text{ moles} \times 32 \text{ g/mol} = 16 \text{ g} \]

### Step 6: Conclusion
Thus, from the electrolysis of 18 grams of water, we will produce:
- **2 grams of hydrogen (H₂)**
- **16 grams of oxygen (O₂)**

### Final Answer
The correct answer is 2 grams of hydrogen and 16 grams of oxygen.

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