Answer:- b. +3
Explanations:- Charge of a metal ion is equal to the number of valence electrons it has as it loses these electrons to have its nearest noble gas like electron configuration.
Al has 3 valence electrons and being a metal it loses all of these and so the charge of Al ion is +3. It could be shown as:

So, the right choice is b. 3+.
Answer:
Sound energy is what we get from an MP3 player
It uses Electrical energy
Explanation:
_2k + _F2—> _2KF
put a 2 before the K and before the KF and you’re all good. it needed to be balanced with the F2
Answer:
The limiting reactant is propene,
.
Explanation:

Moles of nitrogen propene = 2 mol
Moles of oxygen = 10 mol
According to reaction, 2 moles of propene reacts with 9 moles of oxygen gas, then 2 moles of propene will react with:

According to the question, we have 10 moles of oxygen gas, which is more than 9 moles of oxygen gas. This indicates that propene is present in a limiting amount hence, it is a limiting reactant.
The limiting reactant is propene, hence the correct answer is the
.