It's hydroxide ions because acids contain hydrogen ions
Answer: 8.25 moles of oxygen are produced.
Explanation: The reaction follows:

By Stoichiometry,
As, 4 moles of Aluminium is produced by 2 moles of aluminium oxide
11 moles of aluminium will be produced by = 
Now, 2 moles of aluminium oxide produces 3 moles of oxygen, so
5.5 moles of Aluminium oxide will produce = 
Hence, 8.25 moles of oxygen will be produced.
Hello!
To find the mass in grams of 100 atoms of carbon, we need to use Avogadro's number, which is 6.02 x 10^23 grams, and divide that by the total number of atoms.
Next, we would need to find how much one mole of carbon weighs. In this case, it is exactly 12 grams.
1. Divide by Avogadro's number
100 / (6.02 x 10^23) ≈ 1.66 x 10^-22
2. Multiply by one mole of carbon
(1.66 x 10^-22) x 12 ≈ 2.0 x 10^-21
Therefore, the mass of 100 atoms of carbon is equal to about 2.0 x 10^-21 grams.