Hydrogen. The three most common organic compounds are hydrogen, oxygen, and nitrogen.
Answer:

Explanation:
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In this case, since the mole-mole rations consider the amount of the specific ion in the whole compound, we can evidence that the potassium sulfate has two potassium ions in the molecule; in other words, there is a 1:2 mole ratio of the former to the latter; in such a way, we can perform the following proportional factor:

So we cancel out moles of potassium sulfate to obtain:

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It’s blurry sorry. I’m not sure
Answer:
O parallel
Explanation:
For longitudinal waves, the direction of wave motion is parallel to the direction of their propagation.
Longitudinal waves are transferred by a series of rarefaction and compressions along their path.
One important longitudinal waves are sound waves and seismic p-waves.
Transverse waves a propagated perpendicular to the direction of their displacement.