What was a key design change for hfc-134a a/c systems versus cfc-12 a/c systems?

Answer : According to Society of Automotive Engineering (SAE) standards the major key design change that was done for CF-12 A/C systems to HFC-134a A/C systems for the mobile A/C system service is that it provided with new service fittings which reduced the venting of refrigerants into the atmosphere and hence the mixing was also reduced with the ozone.

This new, unique and advanced quick modification has helped a lot in terms of maintaining low level of CFC emission in the environment.

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

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