Q4

q 7 :
after reaction we have 2 moles of NH3 and 1 mole of H2
total moles of the gas = 3 moles
Volume  left for gas after adding 5L of water = 10 L
use
P = nRT/V
T is 300K

could u please do q 9 and 10 also maam
Q 9     2 litres of moist hydrogen were collected over water at 26°C at a total pressure of one atmosphere.On analysis, it was found that the quantity of H2 collected was 0.0788 mole. What is the mole fraction of H2 in moist gas
(1)0.989 (2) 0.897 (3) 0.953 (4) 0.967

Q 10
When CO2 under high pressure is released from a fire extinguisher, particles of solid CO2 are formed, despite the low sublimation temperature (- 77°G) of CO2 at 1.0 atm. It is
(1) the gas does work pushing back the atmosphere using KE of molecules and thus lowering the temperature
(2) volume of the gas is decreased rapidly hence, temperature is lowered
3) both (1) and (2)
4) None of the above

Q 9 Ans
Q 9     2 litres of moist hydrogen were collected over water at 26°C at a total pressure of one atmosphere.On analysis, it was found that the quantity of H2 collected was 0.0788 mole. What is the mole fraction of H2 in moist gas
(1)0.989 (2) 0.897 (3) 0.953 (4) 0.967

First use ideal gas equation to calculate total number of moles of H2 and H2O in moist gas.
PV=n(total)RT
n(total) = n(H2) + n(H2O)
now moles of H2 are given
mole fraction = moles of H2/ n(total)

Q 10
When CO2 under high pressure is released from a fire extinguisher, particles of solid CO2 are formed, despite the low sublimation temperature (- 77°G) of CO2 at 1.0 atm. It is
(1) the gas does work pushing back the atmosphere using KE of molecules and thus lowering the temperature
(2) volume of the gas is decreased rapidly hence, temperature is lowered
3) both (1) and (2)
4) None of the above


In this gas as gas comes out from high pressure to low pressure its going to use its energy in expansion i.e means work is done by gas and hence its temperature goes down.Now 1 and 2 are valid answer as in 1 they are explaining it in terms of KE /work done and in 2 in terms of volume expansion.