8. The following system contains 20.0 psi each of gases A and B in the end bulbs with an evacuated bulb in the centre. Both stopcocks are opened at once. What is the new overall pressure in the system? I literally have no idea how to even start this, I know that the answer is 13.3 psi, but I don't have any clue why or how to get there.

13.3

Explanation:

Before opening the stopcocks you have 40psi in total.

After that, those 40psi will be divided into 3bulbs, so 40/3=13.3psi for the system.

you need to take a look at the periodic system in order to sort these elements into pairs that would most likely exhibit similar chemical properties. first, you need to find elements that are found in the same group (groups are vertical in the periodic system), and then to see whether they have the same valence number. if they meet these criteria, they will have similar properties.

the first pair: ne (neon) and kr (krypton), are noble gases found in group 8

the second pair: li (lithium) and k (potassium), found in group 1

the third pair: s (sulfur) and te (tellurium), found in group 6