0.284 liter is the answer
Given mass of Scandium = 50.0 g
Increase in temperature of the metal when heated = 
Heat absorbed by Scandium = 
The equation showing the relationship between heat, mass, specific heat and temperature change:

Where Q is heat = 
m is mass = 50.0 g
ΔT = 
On plugging in the values and solving for C(specific heat) we get,
=50.0g(C)(
)
C = 0.491
Specific heat of the metal = 0.491
To answer the questions,
(1) Activation energy is the amount of energy that is needed for the reaction to proceed, converting the reactant to products. The answer is letter B.
(2) The rate of chemical reaction normally increases as the reactant concentration is increased. The answer is letter C.