# Chemistry

posted by May

1)A sample of propane gas occupies 625 cm3 at 20.0 °C and 750 torr. What is the final volume in cubic centimeters at -80.0 °C and 750 torr?

2)If oxygen gas is collected over water at 25 °C and 775 torr, what is the partial pressure of the O2? The vapor pressure of water at 25 °C is 23.8 torr.

1. DrBob222

1. (P1V1/T1) = (P2V2/T2)
Remember T must be in kelvin.

2. Ptotal = pO2 + pH2O
Substitute and solve for pO2.

2. May

519 cm3
and 775 torr?

3. DrBob222

I didn't work 1 but 2 can't be right. 775 is Ptotal so how can it be pO2?

4. DrBob222

No, 519 cc isn't correct either. Post your work and I'll find the error.

5. May

1)(750psi)(625cm3)/293k=(v)(750psi)/193k

6. DrBob222

Your set up is right (except for calling torr psi). So your error must be in the math part.

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