my mixture is like this: species (names arp c2cl4 cl c2cl3 c2cl2 cl2 c2 n2) and now i only add in one reaction, which is "1c2cl4 -->1c2cl3 +1cl", i checked carefully the molecular weight of every species, but i still get the warning of "mass imbalance reaction stoichoimetry". Could anyone tell me what is wrong? Thanks.

I not sure if you did it right!! There are couple of possibilities: 1. make that you've selected the RIGHT reactants and products. they shd balance up. tripple check that you've actually selected that in the fluent. 2.check/watch the console if when you click the ok/change the number of messages increase. if say u've observed 3, check when you click ok/change the warning message increase to 4. if it increased then you'd something wrong with your rxn. if it doesn't then, you're alright!! meaning everything is fine. 3.if all fails, then you want to check the molar mass of user defined substance in the mixture!!

All the above work for me. good luck!!

I tired toreproduce your error but i had no luck. I added cl and c2cl3 from the fluent database, created c2cl4 by using c2cl3 as a template and assigned it a molecular weight of 165.8343. There was no mass imbalance in the reaction (win xp). The molecular weight for c2cl3 stored in the thermo.scm is 130.38129 so you might try to c2cl4 a weight of 165.83429 but on my machine fluent always rounds to 4 digits.

RoM