gas laws..

[astarmathsandphysics]

another question

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

[nid404]

answer is 46.02 and 23.01

[astarmathsandphysics]

46 and 23.

[nid404]

isn't density supposed to be in the form g/cm^3......the mass of 1 mole is 46g...so is the density 46g/cm^3....can u just take it like that??

[astarmathsandphysics]

g/cm3 would be 46/22400

[astarmathsandphysics]

cos at ntp 1 mol of gas occupies 22400ml or 22400cm^3

[nid404]

ok got it...thanks sir

[nid404]

another 1

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

[nid404]

can some1 please answer.....i need to leave for my class in an hour...pleeeeaaaaaaase

[astarmathsandphysics]

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



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

[nid404]

thanks a lot astar


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

[nid404]

no one answrin

[Ghost Of Highbury]

astar is offline.

[nid404]

i know dude...some1 else could try

[Ghost Of Highbury]

he is online.~