A sample of gas (1.9 mol) is in a flask at 21 degree C and 697 mm Hg. [he flask

Question

A sample of gas (1.9 mol) is in a flask at 21 degree C and 697 mm Hg. [he flask is now opened and more gas is added to the flask. The new pressure is 795 mm Hg and the temperature is now 26 degree C. How many moles of gas are in the flask? 1.6 2.1 2.9 3.5 0.28 The density of ammonia gas (NH_3) in a 4.32 L container at 837 torr and 45 degree C is g/L. 3.86 0.717 0.432 0.194 4.22 times 10^-2 For the conversion of gaseous water to liquid water at 25 degree C and 1 atm of water vapor pressure the values of Delta G degree, Delta H degree, and Delta S degree are, respectively, negative, negative and negative. zero, negative and positive. zero, positive and negative. positive, negative and negative. positive, positive and positive. A glass bulb contains a mixture of Cl_2 gas and H_2 O gas. Which statement is correct? The molecules of both gases have the same average kinetic energies and Cl_2 molecules have an average speed 0.5 times that of water molecules. The molecules of both gases have the same average kinetic energies and water molecules have an average speed about 4 times that of Cl_2. The molecules of both gases have the same average kinetic energies and water molecules have an average speed 0.5 times that of Cl_2. The average kinetic energy of the water molecules is greater than that of Cl_2 molecule because the average speed of water molecules is 2 times that of Cl_2. The average kinetic energy of the Cl_2 molecules is greater than that of water molecule because the mass of Cl_2 is 4 times that of water and the average speeds are the same at the same temperature. Which of the following correctly ranks the substances in terms of increasing boiling point Kr

Explanation / Answer

Volume of flask from

From PV= nRT, n= no of moles, R= 0.0821 L.atm/mole.K, T =21+273= 294 and P= 697/760 atm

PV= nRT, V= nRT/P = 1.9*0.0821L.atm/mole.K*(21+273)/(697/760) atm=50 L

Let x= additional moles added,

Total moles = 1.9+x, V=50L, P= 795/760 and T= 26+273= 299 K

From n= PV/RT = (795/760)*50/(0.0821*299) =2.13

But 1.9+x= 2.13, x= 2.13-1.9 =0.23 ( Close answer is 0.28)

2.

From PV= nRT, PV= (mass/molar mass)*0.0821*(45+273)

P= 837/760 atm = 1.10 atm, molar mass of NH3 =17

P* molar mass = density*0.0821*318

Density = 0.716 g/L ( b is correct)

3. since heat needs to be removed, deltaH is heat removed from -ve, entropy change is -ve. Entropy change is less-ve than enthalpy change.

deltaG =deltaH-TdeltaS is also -ve, ( a is correct)

Hence the answer is

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