Chemical changes only happen when the object changes form. Color is a physical property because you're not changing the object that you have, compressibility is also a physical property because you still have the same substance before and sfter, malleability again is another physical. Heat of combustion is physical, when you burn things it changes the substance. :)
<span>Answer:
mol Al2O3 x 1 mol Al/ 2 mol Al2O3= .25 mol Al
The balanced equation tells us that it takes 4 moles of Al to produce 2 moles of Al2O3.
0.50 moles Al2O3 x (4 moles Al / 2 moles Al2O3) = 1.0 moles Al
1.0 moles Al x (27.0 g Al / 1 mole Al) = 27.0 g Al</span>
Explanation:
For Mg, (1.2 g Mg/24 g Mg) = 0.05 mol Mg.
For Cl, (3.55 g Cl/35.5 g Cl) = 0.1 mol Cl
So the ratio now is
Mg:Cl = 0.05 : 0.1 = 1:2
I got the 1:2 ratio by dividing both by the smallest number, which is 0.05 mol. Therefore, the empirical for formula of the substance is 
I think its an Ionic bond although i am not sure about
