Answer:
Energy is used to break bonds in reactants, and energy is released when new bonds form in products. ... In other chemical reactions, it takes more energy to break bonds in reactants than is released when bonds form in products. These reactions, called endothermic reactions, absorb energy.
Explanation:
Here we have to choose the challenge which is faced by the scientist to make a hydrogen fuel cell by using water.
The challenge that the scientists are facing a. decomposition of water requires a high energy.
For the generation of fuel cells by hydrogen the use of water (H₂O) is a challenging task as the H-O bond in water is so strong and need high activation energy.
As per the mechanism of hydrogen fuel cell generation of H₂ is compulsory. Water remains in its solution as H₂O⇔H⁺ + OH⁻. The breaking of hydroxide ion (OH⁻) to form free hydrogen need a high energy, which cannot meet easily by any energy source.
The sun is always a renewable energy source as the energy of sun is infinitive.
The decomposition of water will only produce oxygen (O₂) and hydrogen (H₂) among which H₂ will be used in the fuel cell and O₂ is not at all harmful.
The excess O₂ is always good for the environment as it is the breathing source in the living system.
Answer:
deposition is the change from gas to solid
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