5 L OF H2 GAS WAS COLLECTED OVER WATER AT 25 CELCIUS AND 750 MM PRESSURE CALCULATE THE VOLUME OF DRY H2 AT STP AQUEOUS TENSION AT 25 CELCIUS IS 23 MM

Answer 1

Note the correct spelling of celsius.
Please don't use all caps. It makes it harder to read.

Use (P1V1/T1) = (P2V2/T2)
You know V1 and T1, P1 = 750 mm-23 mm = ?
P2 and T2 are at STP. I assume you know those. Solve for V2.