Post by: nid404 on September 30, 2009, 07:04:16 am
2) The density of a gas at 27 degrees celcius and 760mm pressure was found to be 3g/l. Find out the temperature at which the density will become 2.4g/l, keeping pressure constant
Please answer
Thanks :)
Post by: nid404 on September 30, 2009, 07:10:04 am
Please answer the first one....astar..or adi and slvri
Post by: astarmathsandphysics on September 30, 2009, 07:32:35 am
Post by: nid404 on September 30, 2009, 08:09:54 am
Post by: astarmathsandphysics on September 30, 2009, 08:48:25 am
2) The density of a gas at 27 degrees celcius and 760mm pressure was found to be 3g/l. Find out the temperature at which the density will become 2.4g/l, keeping pressure constant
1/ the volume is constant since it is the volume of the room.
Much more borderline than before, but still I say it wont melt.I think it will not melt since the temp of the fire is typically up to 1000K so the pressure will be less than 10^6
2)P1/d1=P2/d2
temp will be 2.4/3 *300=240K
Post by: nid404 on September 30, 2009, 08:56:14 am
I've modified the question
Post by: nid404 on September 30, 2009, 02:15:28 pm
Post by: slvri on September 30, 2009, 02:39:29 pm
1) An iron cylinder contains He at a pressure of 250KPa at 300K. the cylinder can withstand a pressure of 1X10^6 Pa. The room in which the cylinder is placed catches fire. Predict whether the cylinder will blow up before it melts or not.....this is physics right..........u guys are already so far ahead? i dont know how to answer this q cuz i aint studied this.........sory :-[
2) The density of a gas at 27 degrees celcius and 760mm pressure was found to be 3g/l. Find out the temperature at which the density will become 2.4g/l, keeping pressure constant
Please answer
Thanks :)
Post by: astarmathsandphysics on September 30, 2009, 02:53:40 pm
Post by: nid404 on September 30, 2009, 03:10:56 pm
but shouldn't the second be 1/T1d1=1/T2d2
considering vapour density :-\
Post by: nid404 on September 30, 2009, 03:13:54 pm
this is physics right..........u guys are already so far ahead? i dont know how to answer this q cuz i aint studied this.........sory :-[
No problem slvri
Post by: astarmathsandphysics on September 30, 2009, 03:16:21 pm
Post by: nid404 on September 30, 2009, 03:49:37 pm
pV= K but d=m/V soV=M/d so p/d=K
In this case the pressure is constant ???
so isn't it
t1d1=t2d2
300KX3=2.4Xt2
t2=375K
I'm confused :-\
Post by: astarmathsandphysics on September 30, 2009, 06:50:15 pm
Post by: nid404 on October 04, 2009, 12:07:58 pm
0.23g of a volatile solute displaced 112ml of air at NTP. Calculate the vapour density and the molecular weight of the substabce
Post by: astarmathsandphysics on October 04, 2009, 12:32:02 pm
0.23g of a volatile solute displaced 112ml of air at NTP. Calculate the vapour density and the molecular weight of the substabce
density =0.23g/112cm^3 =2.3*10^-4 kg /112*10-6 m^3 =2.05 KG/m^3
1 mol of a gas occupies 2240ml at ntp so we have 112/2240=0.5 mols.
0.5 mols weighs 0.23g so 1 mole weighs 0.23/0.05=46g
1 mol contains 6.023*10^23 molecules so 1 molecule weighs 0.046/6.023*10^23 kg
Post by: nid404 on October 04, 2009, 12:43:06 pm
Post by: astarmathsandphysics on October 04, 2009, 12:49:02 pm
Post by: nid404 on October 04, 2009, 12:52:06 pm
Post by: astarmathsandphysics on October 04, 2009, 12:57:56 pm
Post by: astarmathsandphysics on October 04, 2009, 12:59:34 pm
Post by: nid404 on October 04, 2009, 01:01:45 pm
Post by: nid404 on October 06, 2009, 07:27:42 am
The pressure exerted by a 12g of ideal gas at temp t degrees Celsius in a vessel V Litre is 1atm. When the temp is increased by 10 degrees at the same volume, the pressure increases by 10%. Calculate the temp t and voluume V.(molecular weight of gas=120)
ans
t=-173 degrees
V-0.82 L
Post by: nid404 on October 06, 2009, 08:23:16 am
Post by: astarmathsandphysics on October 06, 2009, 08:38:04 am
ans
t=-173 degrees
V-0.82 L
0.1 mol of gas so pV=nRT so V=nRT/p=0.1*8.31*100/100000=8.31*10^-4 m3 or 0.83 ltres
Post by: nid404 on October 06, 2009, 08:45:39 am
one more please
A balloon filled with helium rises to a certain height at which it gets fully inflated to a volume of 100000 litres. If at this altittude the pressure is 0.02 atm and temp is 268K, what weight of helium is required to fully inflate the balloon
when i used PV=nRT i don't get the right answer
Ans-36.36g
Post by: nid404 on October 06, 2009, 03:22:40 pm
Post by: Ghost Of Highbury on October 06, 2009, 03:36:25 pm
Post by: nid404 on October 06, 2009, 03:37:12 pm
Post by: Ghost Of Highbury on October 06, 2009, 03:38:27 pm
Post by: astarmathsandphysics on October 06, 2009, 03:40:15 pm
A balloon filled with helium rises to a certain height at which it gets fully inflated to a volume of 100000 litres. If at this altittude the pressure is 0.02 atm and temp is 268K, what weight of helium is required to fully inflate the balloon
when i used PV=nRT i don't get the right answer
Ans-36.36g
n=pV/RT=(0.02*10^5*100)/(8.31*268)=89.8 mols
i mole of helium weighs 4g so 89.8 mols weighs 4*89.8=359.2g
Post by: Ghost Of Highbury on October 06, 2009, 03:43:21 pm
astar's answer = 359.2 ]
??
misprint?
Post by: astarmathsandphysics on October 06, 2009, 03:44:27 pm
Post by: Ghost Of Highbury on October 06, 2009, 03:48:16 pm
the answer says - 36g
Post by: astarmathsandphysics on October 06, 2009, 03:51:17 pm
Post by: Ghost Of Highbury on October 06, 2009, 03:51:48 pm
Post by: nid404 on October 06, 2009, 07:09:42 pm
Post by: nid404 on October 13, 2009, 07:47:59 am
Actually i don't know the formulae for finding out partial pressure...wet and dry gas and stuff....cuz i joined classes late
1) Oxygen is collected over water at 20 degrees Celsius . The pressure inside is shown by the gas is 740mm of Hg. What is the pressure of O2 alone if V.P of H2O is 18mm at 20 degrees celsius
do u simply do 740mm-18mm?? Please help
Post by: astarmathsandphysics on October 13, 2009, 07:53:08 am
Post by: @d!_†oX!© on October 13, 2009, 07:54:13 am
pV= K but d=m/V soV=M/d so p/d=Kummmm.....i dont really know i need this or not in my exams bt just for my curiosity....cud u plsss expand how u got dese....i understood d first 3.....bt how d last one?????
Thanks in advance....By the way is this A levels???
Post by: nid404 on October 13, 2009, 07:55:43 am
Exactly
THanks a lot astar :) U rock!!
Post by: astarmathsandphysics on October 13, 2009, 08:30:33 am
d=m/V so dV=m so V=m/d so pm/d =K so p/d=K/m =C another constant.
Not the mass m of the gass is fixed so now pressure/density=constant
Post by: nid404 on October 13, 2009, 08:33:40 am
For 10 min each, at 27 degrees celsius,from 2 identical holes,nitrogen and an unknown gas are leaked into a common vessel of 3 litre capacity. The resulting pressure is 4.18 bar and mixture contains 0.4 mole of nitrogen. WHat is the molar mass of the unknown gas?
Post by: @d!_†oX!© on October 13, 2009, 08:49:01 am
pV= Kohhkkk......Thanks astar......By the way is this a levels or igcse?????this wont come in my exam rite????
d=m/V so dV=m so V=m/d so pm/d =K so p/d=K/m =C another constant.
Not the mass m of the gass is fixed so now pressure/density=constant
Post by: nid404 on October 13, 2009, 08:49:53 am
ohhkkk......Thanks astar......By the way is this a levels or igcse?????this wont come in my exam rite????
nope it won't....it's an iit question....don't worry
Post by: astarmathsandphysics on October 13, 2009, 09:06:51 am
pv=nRT
4.18*10^5*0.003=n*8.31*300 so n=0.503 moles so 0.103 moles unknown gas. The kinetic energies are the same(=3/2kT=1/2mv^2) so v=k/sqrt(m) the unknown gas diffuses at 1/4 the rate of nitogen so its mass must be 16 times greater 16*15=240g/mol
Post by: nid404 on October 13, 2009, 09:22:06 am
like why did u take V=0.003?? and the kinetic energy part of it
Post by: astarmathsandphysics on October 13, 2009, 09:57:02 am
The kinetic energy of a gas molecule is 3/2kT so all the molecules have the same energy. The kinetic energy is given by 1/2mv^2 s0o mv^2 for nitrogen =mv^2 for the unknown gas so m is inversly proprtional to v^2. I will make a correction to my earlier post.
Post by: nid404 on October 13, 2009, 04:38:31 pm
Post by: nid404 on October 20, 2009, 07:22:40 am
A stopclock, connecting two bulbs of volumes 5l and 10l containing an ideal gas at 9atm and 6atm respectively is opened. What is the final pressure in the two bulbs??
Post by: nid404 on October 20, 2009, 07:40:49 am
An open flask contains air at 27degrees celsius.Calculate the temperature at which it should be heated so that
a)1/3 of the air measured at 27degrees escapes out
b)1/3 of air measured at final temp escapes out
Post by: astarmathsandphysics on October 20, 2009, 08:10:08 am
partial pressures question
pressure of gas 1 =5/(5+10)*9=3atm
pressure gas 2 =10/(5+10)*6=4atm
partial =7atm
Post by: astarmathsandphysics on October 20, 2009, 08:14:39 am
a)1/3 of the air measured at 27degrees escapes out
b)1/3 of air measured at final temp escapes out
1/3 escapes so volume is 3/2 of original volume so temple is 3/2*(273+27)=450K
I dont understand B. 1/3 of the air is 1/3 of the air does it mean the gas is heated again? If so 3/2*(450)=675K
Post by: nid404 on October 20, 2009, 08:23:29 am
thanks for the other ones tho :)
Post by: nid404 on October 20, 2009, 08:32:26 am
how is 10/15=4
Post by: Light on October 20, 2009, 08:55:28 am
Post by: astarmathsandphysics on October 20, 2009, 08:57:13 am
Post by: nid404 on October 20, 2009, 08:57:45 am
it is 10/15 * 6atm=4.mole fraction * pressure. ::)
thanks. I just started with the concept...so i really don't know
Post by: astarmathsandphysics on October 20, 2009, 09:02:34 am
Post by: nid404 on October 20, 2009, 09:03:02 am
You calculae the pressure that would be exerted by each gas if it occupied the whole volume then add them
thanks sir