The best and most correct answer among the choices provided by the question is the second choice , b. sodium hydroxide .
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Answer: Evaporation of salt water
Explanation: During the process of evaporating salt water which involves simple distillation, pure water is separated with salt molecules.
When heated water evaporates from the solution since it is less dense. When condensed it becomes pure water and salt is left out since it is more denser.
It changes to chemical energy
The mass of hydrogen gas is 1.00794 u ± 0.00001 u. I hope this helps you out!!