<span>Total mass = 2.75g
Mass % of Mg = 1.0g x 100/2.75g = 36.36 %
Mass % of O = 1.75g x 100/2.75g = 63.64 %
Mol of Mg = 36.36/24 = 1.515
Mol of O = 63.64/16 = 3.977
Ratio of Mol of Mg and O in the substance = (1.515 : 3.977) x 2 = 3 : 8
The empirical formula of substance is Mg3O8</span>
We will use Arrehenius equation
lnK = lnA -( Ea / RT)
R = gas constant = 8.314 J / mol K
T = temperature = 25 C = 298 K
A = frequency factor
ln A = ln (1.5×10 ^11) = 25.73
Ea = activation energy = 56.9 kj/mol = 56900 J / mol
lnK = 25.73 - (56900 / 8.314 X 298) = 2.76
Taking antilog
K = 15.8
The answer is the 3rd choice
