I'm not sure but i would say C.storing the heat energy.
Answer: 19.4 g/cm3
Explanation: density is the relationship between mass over volume.
So density of gold is 15.7g/0.81cm3 = 19.4 g/cm3
<u>Answer:</u> The temperature of the system will be 1622 K
<u>Explanation:</u>
The equation relating the pre-exponential factor and activation energy follows:

where,
D = diffusion coefficient = 
= pre-exponential constant = 
= activation energy of iron in cobalt = 273,300 J/mol
R = Gas constant = 8.314 J/mol.K
T = temperature = ?
Putting values in above equation, we get:

Hence, the temperature of the system will be 1622 K
Answer: can be considered to be both an acid and a base
Explanation:
7 valence electrons in an atom