The correct answer is C.
Burning is a chemical change. It's a chemical process that includes oxygen.
All the other options are a change of state: form solid to liquid, or from liquid to gas (as in the last one).
I think the family of Group 2 metals are most likely to form a 2+ion.
You are given
300 grams of FeCr2O7. You are required to get the mass of O2 in grams. The first
thing to do is to find a reaction between FeCr2O7 and O2. The balanced chemical
reaction is 2Fe + 6Cr + 21/2O2 -> Fe2(Cr2O7)3. The molar mass of Fe2(Cr2O7)3
is 759.65 grams per mole and 32 grams per mole for O2.
<span>
300g Fe2(Cr2O7)3
(1 mol Fe2(Cr2O7)3/759.65 g Fe2(Cr2O7)3)(21/2 mol O2/1 mole Fe2(Cr2O7)3)(32 g
O2/1 mole O2) = <u>132.7 g O2</u></span>
Ca=40g
P=31g
Ca3=120g
P2=62g
Ca3P2=182g
Ca3/Ca3p2=120/182=0.6593=approximately 65.93%
