According to the following balanced reaction, how many moles of NO are formed from 12.66 moles of NO2 if there is plenty of water present? 3 NO2(g) + H2O(l) → 2 HNO3(aq) + NO(g)

The given equation is
3 NO2(g) + H2O(l) → 2 HNO3(aq) + NO(g)
It is clear from the above equation that For every 3 moles of NO2 used, 1 mole of NO is produced.
Therefore, by using concept of mole ratio,
12.66 mol NO2 x (1 mol of NO / 3 mols of NO2)= required moles of NO
12.66 x 1/ 3 = 4.22 moles of NO
Therefore, 4.22 moles of NO produced in the given reaction.

3 NO2(g) + H2O(l) → 2 HNO3(aq) + NO(g)

From the balanced reaction, we can see the ratio mol balance to coefficient.
Mol NO : mol NO2 = 1:3
Mol NO=(1 x mol NO2) / 3 M
Mol NO = (1 x 12.66) / = 4.22

The given balanced chemical reaction is:
3 NO2 (g) + H2O (l) -> 2 HNO3 (aq) + NO (g)
In this reaction, nitrogen dioxide (NO2) reacts with water (H2O) to form nitric acid (HNO3) and nitric oxide (NO).
Using stoichiometry, 3 moles of nitrogen dioxide reacts with 1 mole of water to form 2 moles of nitric acid and 1 mole of nitric oxide.
In other words, if plenty of water is present, 3 moles of nitrogen dioxide will form 1 mole of nitric oxide. It also means that each mole of nitrogen dioxide will form 1/3 moles of nitric oxide.
In this case, 12.66 moles of nitrogen dioxide is present.
Hence, the number of moles of nitric oxide formed are:
12.66 moles x 1/3 = 4.22 moles.
Thus, using this balanced chemical reaction, we can say that if 12.66 moles of NO2 react with plenty of water, 4.22 moles of NO are formed.
Hope this helps.