Answer:
Transitional metals are good conductors of both heat and electricity.
But since there aren't any. It could be Calcium.
8.4 moles equals 469.14g Fe
Answer:
Reaction type: Single displacement
Reactant: Magnesium
Product: Dihydrogen - H2
Answer : The value of rate constant is, 
Explanation :
First we have to calculate the rate constant, we use the formula :
Expression for rate law for first order kinetics is given by:

where,
k = rate constant = ?
t = time passed by the sample = 20 min
a = let initial amount of the reactant = 100 g
a - x = amount left after decay process = 100 - 85 = 15 g
Now put all the given values in above equation, we get


Therefore, the value of rate constant is, 
Answer:
One mole is defined as the amount of substance containing as many elementary entities (atoms, molecules, ions, electrons, radicals, etc.) as there are atoms in 12 grams of carbon-12 (6.023 x 1023). The mass of one mole of a substance equals its relative molecular mass expressed in grams. Also spelled as mol.