To solve this problem, we need to use the given mass ratio between hydrogen and oxygen when they combine to form water, which is 1:8 by mass. This means that for every 1 part by mass of hydrogen, 8 parts by mass of oxygen are needed.
Let's break down the steps:
1. Understand the given ratio: The ratio of hydrogen to oxygen by mass is 1:8. This implies:
[tex]\[
\text{mass of oxygen} = 8 \times \text{mass of hydrogen}
\][/tex]
2. Given mass of hydrogen: You are given that the mass of hydrogen is 3 grams.
3. Calculate the required mass of oxygen: Using the ratio from step 1, calculate the mass of oxygen needed:
[tex]\[
\text{mass of oxygen} = 8 \times 3 \, \text{grams}
\][/tex]
4. Perform the multiplication:
[tex]\[
8 \times 3 = 24 \, \text{grams}
\][/tex]
Therefore, the mass of oxygen gas required to react completely with 3 grams of hydrogen gas is 24 grams.