J.R. S. answered 03/11/22
Ph.D. University Professor with 10+ years Tutoring Experience
3CH3Br + NH3 ==> (CH3)3N + 3HBr ... ΔH = 73KJ
6CH3Br + 2NH3 ==> 2(CH3)3N + 6HBr This is 2x the original. Multiply 73 kJ by 2
1/3(CH3)3N + HBr ==> CH3Br + 1/3 NH3 This is the reverse of the original and is 1/3 so divide 73 kJ by 3 and change the sign
(CH3)3N + 3HBr ==> 3CH3Br + NH3 This is the reverse of the original so simply change the sign