2.3 mols of Al*26.98 molar mass of Al=62.054g
-20.16 KJ of heat are released by the reaction of 25.0 g of Na2O2.
Explanation:
Given:
mass of Na2O2 = 25 grams
atomic mass of Na2O2 = 78 gram/mole
number of mole = 
= 
=0. 32 moles
The balanced equation for the reaction:
2 Na2O2(s) + 2 H2O(l) → 4 NaOH(aq) + O2(g) ∆Hο = −126 kJ
It can be seen that 126 KJ of energy is released when 2 moles of Na2O2 undergoes reaction.
similarly 0.3 moles of Na2O2 on reaction would give:
= 
x = 
= -20.16 KJ
Thus, - 20.16 KJ of energy will be released.
Answer:
The mass ratio of zinc to sulfide is 85:42.
2.5559 kg of Zn are in 3.82 kg of ZnS.
Explanation:
a) Mass of zinc sulfide = 254 g
Mass of zinc in a zinc sulfide sample = 170 g
Mass of sulfide in zinc sulfide sample = x
254 g = 170 g+ x
x = 84 g
The mass ratio of zinc to sulfide:

b) Mass of zincsulfide sample = 3.83 kg
The mass ratio of zinc to sulfide is 85:42.
Let the mass of zinc and sulfide be 85x and 42x respectively:
85 x+ 42 x=3.82 kg
x =0.03007 kg
Mass of an zinc= 85x=85 × 0.03007 kg= 2.5559 kg