Answer:
a) 
is the mass of 1 mole of bricks.
b) 
moles of bricks have a mass equal to the mass of the Earth.
Explanation:
a) Mass of brick = 4.0 kg
1 mole = 
particles/ atoms/molecules
Mass of 
bricks :
is the mass of 1 mole of bricks.
b)
Mass of the Earth = M = 
Mass of 1 mole of brick = m=
Let the moles of brick with equal mass of the Earth be x.
moles of bricks have a mass equal to the mass of the Earth.
Calcium is in group 2A because it has two valence electrons and an oxidation state of 2+. Hope this is accurate & helpful! Enjoy your evening.
Answer:
we need to know which atom you're talking about and then you need to say what the mass number is then we can tell how many electrons there are.
(I think)
The amount ( in moles of excess reactant that is left is 0.206 moles
Explanation
FeS(s) + 2HCl (aq) → FeCl2 (s) + H2S (g)
- by use of mole ratio of FeS: HCl which is 1:2 this means that 0.223 mole of FeS reacted completely with 0.223 x 2/1 =0.446 moles 0f FeCl2.
- HCl was in excess because 0.446 moles of HCl reacted and initially there was 0.652 moles.
- Therefore the amount that was left
= 0.652- 0.446 =0.206 moles
