Hydrogen and oxygen combine in the ratio of `1 : 8` by mass to form water. What mass of oxygen gas would be required to react completely with 3 g of hydrogen gas?

Explanation

To solve the problem, we need to determine how much oxygen gas is required to react completely with 3 grams of hydrogen gas, given that hydrogen and oxygen combine in the ratio of 1:8 by mass to form water.

### Step-by-step Solution:

1. **Understand the Mass Ratio**:
The problem states that hydrogen (H) and oxygen (O) combine in the ratio of 1:8 by mass. This means that for every 1 gram of hydrogen, 8 grams of oxygen are needed.

2. **Determine the Mass of Hydrogen**:
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