Most of the NADH that delivers electrons to the electron transport chain comes from the citric acid cycle and or the kreb's cycle.
Hey, for #1, it's 1, 1, 1 because it's already balanced!
For #2, it's 1, 2, 1, 1 since the product side has 2 Cl's but left side only had 1.
The Lewis structure the student drew is incorrect. The total number of electrons in bonds and lone pairs is equal to the total number of valence electrons available, then a valid Lewis structure is produced.
The correct structure is the following:
The structure that was drawn by the student was incorrect because the total number of electrons around Oxygen were incorrect, there were 6 instead of 8, which was against the octet rule. The correct structure should have 8 electrons around each atom.