00:01
Okay, question number 20.
00:05
The density of a gas, okay, the density of gas is 3 .48 gram liter.
00:14
At the standard temperature pressure, which means the time, the temperature we have 273 kelvin, the pressure we have 1 atmospheric.
00:28
Okay, what is the molecular weight? so we have to find the molecular weight, denoted by.
00:36
M okay using the general gas equation which is pv is equal to n r t where n is equals to mass over molar mass replace n from this value m divided by the capital m r t here the density is equal to mass over volume so p is equal to m divided by capital m v r t here so, density is equal to m over v here, d r t divided by m.
01:31
So we have to find the molar mass m.
01:35
So really rearrange the value, we get the molar mass here, the drt divided by b.
01:45
Okay, simply substitute the value here, which is 3 .48 gram, liter density, multiply the you know r is the universal gas constant which value is 0 .0 8205 litter atmospheric per kelvin and per mole multiply temperature we have to 7 trees stp temperature okay divided by the pressure we have one atmospheric first cancel the units here atm to atm liter to liter it's a gram per liter it's a gram per liter it's a per liter okay later later kelvin to kelvin okay the molar weights come out the molar weight came out 77 .9 roundabout gives 78 it gives 78 gram per more okay the correct answer is d we have 78 gram per more okay question number 21 we have we have to find the number of moles in this question where okay where the value of r is are the universal gas constant value of r is 0 .082 0 .06 liter atmospheric per kelvin and per more okay and the pressure is okay at the pressure we have a pressure is seven seven seven seven seven to seven to seven to seven centimeter m m m g convert into the m m g form simply multiply by 10 which is 760 m m g okay we have a volume so volume we have it's 2 liter so volume we have a 1 liter volume we have 1 liter and temperature we have 18 degrees celsius converted into the kelvin form which is 2 91 kelvin 1.
04:49
Okay, find the number of moles...