[eakhd]

Hello! I have this question:
A mixture of He and O2 gases is used by deep-sea divers. The pressure of the oxygen gas in the tank must be the same as what the diver would ordinarily breathe. If the total pressure of the tank is 8.0 atm, what percent of the mixture should be O2.

Are we supposed to know what pressure the diver ordinarily breathes? I know I would just calculate what that is over 8.0 atm. But I’m not sure where we’re supposed to know, sorry if this is supposed to be common information. I’m genuinely confused, is there a way to find that through the problem?

[Hunter2]

The pressure in the tank and what will be breathed is different. The Tank has higher pressure to get more gas stored. The breathing pressure is approx. 1 atm.
Oxygen, nitrogen helium mixtures are called Triox or Trimex.
Refer to this.

[Borek]

Are we supposed to know what pressure the diver ordinarily breathes?

Yes. Think standard pressure and composition of air. This definitely counts as a common knowledge.

Plus what Hunter wrote - pressure in the tank is not what you are breathing while diving, air is delivered at the pressure consistent with the pressure at the depth the diver is at. 8 atm would mean around 70 meters.