Keeping raw chemistry - does it eat oxygen?

My understanding is that Sodium Sulfite and HQ are responsible for oxygen consuming property of developers and HCA. Then, here's a question I'm hoping someone can answer.

If I were to purchase 5 lbs of Sodium Sulfite (it's cheap) and mix it for use as HCA on as-needed basis, kept in a container that it ships in (for example from Photographers' Formulary), would I still have an issue of powdered form of this component reacting with oxygen and basically "going bad?"

I know many on APUG mix their own chemistry. How do you deal with raw chemistry freshness?

I transfer the sodium sulfite that comes in a plastic pail to mason jars. They're cheap and being glass offer the best protection. Your sulfite should keep for years without oxidizing. Make sure that you label them with the contents.

I have a 5# brown glass jar of Kodak hydroquinone that is decades old. Other than showing a slight violet tinge it is still active as a developing agent.

Keep raw chemicals in glass jars. Brown glass is best for developing agents. No reason to worry.

Speaking of mason jars/glass jars - any particular model that is better than the other?

The jar depends on the chemical. If my experience is that it is free flowing, and I use a lot per liter, I go with standard mason jars, or wide mouth packer type boston amber jars (is I think their trade name).

If it is a developing agent, etc. and I need to measure out small amounts, I pack them into 125mL mason jars, so the whole top of the jar can have material spooned from it.

If it really likes to oxidise, I blanket it with nitrogen (on very low pressure at the regualtor), pack it in a glass container and store it in the freezer.
My glycin has kept nice and white for me this way for more than 2 years, and this is for a chemical that usually oxidizes by the week into brown ucks.

The other thing to watch for is deliquescent materials. Thiocyanates are one I am familair with, as are hydroxides.
These suck water out of the air before you know it. I look up solubility in the CRC bible, and then store them as stock solutions in reverse osmisis filtered water that has been pre bioled and cooled to drive off all dissolved oxgen in it.