Answer:
I believe your answer will be 3--
As the fuel burns, chemical reactions occur within the fuel, breaking up molecules, forming new molecules, and releasing energy. The energy is released as heat, and allows parts of the engine to move. The chemical energy is transformed into thermal energy.
Explanation:
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Answer:
The balanced half-reaction for the reduction of dichromate ion to chromium ion in acidic aqueous solution:

Explanation:
The reaction :

Balancing of reaction in an acidic medium:
Step 1: Balance the atoms in the reaction:

Step 2: Balance oxygen atom by adding water on the side where no oxygen or less oxygen atom is present;

Step 3: Balance the hydrogen atom by adding hydrogen ions on the side where water is absent:

Step 4: Now balance charge by adding electrons on the side where more positive charge is present

The balanced half-reaction for the reduction of dichromate ion to chromium ion in acidic aqueous solution:

Scandium forms one ion, Sc3+, with an electron configuration of 1s2 2s2 2p6 3s2 3p6