What is the pressure exerted by hydrogen gas collected in water at 21.0°C, given that the vapor pressure of water at this temperature is 20.0 torr and the total pressure is 750. torr?
A 770 torr
B 730 torr
C 750 torr

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

i'm pretty sure its b i might be wrong though!

explanation:

0.07 g/cm³

1.37 g/cm³