Calculate the standard enthalpy change for the reaction

Question

2A+B->2C+D
Use the following data:
Substance
A=-257kj/mol
B=-413kj/mol
C=189kj/mol
D=-475kj/mol
For the reaction given , how much heat is absorbed when 3.00mol of A react?

Answer 1

Is A,B,C,D standard heats of formation?

If so, then by Hess' Law..

Hr=2(C)+D-2(A)-B
That hear of reaction is when 2 moles of A react, so, multiply it by 1.5.

Answer 2

-297KJ/MOL