The best answer between the two choices would be the first option TRUE because the scientific method is used to do more advance research and investigation on things.
Answer:
6.3 moles
Explanation:
From the balanced equation of reaction:

2 moles of aluminium reacts with 3 moles of chlorine gas to form 2 moles of AlCl3.
Therefore, 1 mole of chlorine will require: 2 x 1/3 = 0.67 mole of aluminium.
Hence, 0.67 mole of aluminium will be needed for 1 mole of chlorine. If 7 moles of aluminium is present, then:
7 - 0.67 = 6.33 moles of aluminium will be left.
To the nearest 0.1, it means 6.3 moles of aluminium will be left.
The half-life of a radioactive compound is the time taken for that said isotope to decay or disintegrate so that only half of the initial atoms remain in that compound. During the decay process, the isotope will give off energy and matter, and the way to depict this is indicated by t 1/2.