G Chem Question plz help

[luv8724]

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how much heat is released when 120g of Ca(s) reacts completely with excess O2(g)?

2Ca(s) + O2(g) --> 2CaO(s) H= -1271KJ

Ans = 1907KJ

Can someone explain this to me

 

[herkulease]

this is essentially a stoichiometry problem.

covert 120g of Ca to mols.

then 3 Mols of Ca (-1271KJ/2 Mols of Ca)

Mols of Ca cancel out.

multiple and then divide and your left with -1906.5KJ or -1907KJ

 

[iamgosu]

hercules is the man!