[puremercury]

my fisr post. 
A question from a past Chem contest: A U-tube mercury manometer is open on the right
arm and connected to a gas sample at the other arm. The atmospheric pressure is 101
kPa and the difference in levels of mercury is 20 cm.
What is the pressure of the gas in the bulb?

Any idea how you get the answer of 128 kPa. i thought you have to convert 20 cm into kpa which is around 267kpa. not sure how it goes from there.

[Yggdrasil]

Are you sure that 20 cm = 267 kPa?  I think it's significantly lower than that.

Recall that 760 mmHg is approximately equivalent to 101kPa.

So 20 cmHg * (10 mm / 1 cm) = 200 mmHg * (101 kPa / 760 mmHg)= 26.6 kPa

Since this is the difference between atmospheric pressure and the pressure of the gas sample, you just add 27 kPa to atmospheric pressure to get the answer.

[Donaldson Tan]

This thread doesn't sound so chemistry...

[xiankai]

this brings back memories...

http://www.chemicalforums.com/index.php?topic=3476.msg15014#msg15014

its wierd, they dont tell u whether the level is higher or lower.

impossible to tell the pressure of the bulb, imho