Can someone please do these chemistry questions with me, I only have these two left?

The volume of a sample of oxygen is 250.8 ml when the pressure is 0.491 atm and the temperature is 30.5 ºC. At what temperature is the volume 1480.6 L and the pressure 0.240 atm?

Select one:

a. 603

b. 876

c. 88.0

d. -168

The pressure of a sample of gas increases from 401.6 mm Hg to 723.3 mm Hg. If the volume is constant and the temperature of the gas was -7.2 ºC, what is the new gas temperature?

Select one:

a. 479

b. -13.0

c. 148

d. -4.00

2 Answers

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  • 5 months ago
    Best answer

    Two questions left ....

    Wouldn't it be a shame to say you couldn't do all of the questions?

    Simply use the combined gas law and "plug and chug", making sure the pressure units are the same, the volume units are the same and temperature is in Kelvin. Based on your answer choices, I would suppose that the volume should be 1480.6 mL

    P1V1 / T1 = P2V2 / T2 .......... combined gas law

    T2 = P2V2T1 / (P1V1) ........... solve for T2

    T2 = 0.240 atm x 1480.6mL x 303.65K / 0.491 atm / 250.8 mL

    T2 = 876 K ............ to three significant digits

    The second question is done the same way, except you can cancel out the constant volume.

    P1V1 / T1 = P2V2 / T2 .......... combined gas law

    T2 = P2T1 / P1 ...................... solve for T2

    T2 = 723.3 torr x 265.95 K / 401.6 torr

    T2 = do the math ......... There is no need to convert to Celsius, because it would appear that the answer choices are in Kelvin, although both of these questions should have had the units along with the numbers. Of course, if these are supposed to be in Kelvin, having a negative temperature is silly because the lowest possible Kelvin temperature is absolute zero. If the temperature was to be in Celsius, then 206C should have been in the list.

  • 5 months ago

    (30.5 + 273.15)K x (1480.6 L / 0.2508 L) x (0.491 atm / 0.240 atm) = 3667362 K

    That's an absurd temperature (and nowhere near any of the proposed answers) so there is something not right about the given numbers or units or both. In particular, "250.8 ml" and "1480.6 L" are especially suspicious.

    [Besides, all the proposed answers are wrong because they have no units.]

    ------------------------

    (-7.2 + 273.15) K x (723.3 mmHg / 401.6 mmHg) = 478.99 K = 479 K

    So answer a. [Although all of the proposed answers are wrong because they have no units.]

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