1Al2(SO4)3 + 3ZnCl2 → 2AlCl3 + 3ZnSO4
The coefficients represents moles. There is 1 mole of Aluminum Sulfate, 3 moles of Zinc(II) Chloride, 2 moles of Aluminum Chloride, and 3 moles of Zinc(II) Sulfate.
Now add all the coefficients/moles.
9 is the sum of all the coefficients.
It's A. volume
Pressure =

with const depends on the chosen unit of volume
I think so...
Answer;
-Chlorine is more reactive than silicon
Explanation;
-As you move across a period, the nuclear charge will increase; the number of energy levels will stay the same, so there is a stronger and stronger attraction for the electrons.
-The electrons are being held more tightly as you move across a period. It becomes more and more difficult to lose electrons and consequently the reactivity of non metals increases as you go from left to right across the periodic table; Therefore; chlorine is more reactive than silicon.