A stock solution of perchloric acid is 70.5% by mass HClO_4 and 29.5% by mass wa

Question

A stock solution of perchloric acid is 70.5% by mass HClO_4 and 29.5% by mass water. Then density of the solution is 1.67 g/mL at 20 degree C. What is the molarity of the solution?_______12.5 M 11.7 M 10.5M 5.5 M The atmospheric pressure on Pluto is approximately 0.3 Pa. Convert this pressure to atmospheres [1 atm = 101325 Pa]___________3 times 10^4 atm 0.08 atm 3 times 10^-6 atm 0 3 atm A sample of oxygen occupies 44.40 mL at 1.20 atm. What will be the volume of the oxygen if the pressure is reduced to 0 80 atm at a constant temperature?_______________0.022 mL 67 mL 43 mL 29 mL A sample of gas has a volume of 3.80 L at an unknown temperature. When the sample is placed into a cold bath at -5.00 degree C, its volume decreases to 1.12 L. What was the initial temperature of the sample, in degree C?__________-194 degree C 5.00 degree C 636 degree C 909 degree C A cylinder fitted with a piston contains 0 333 moles of gas with a volume of 8.27 L. Determine the total volume of gas in the cylinder after 0.187 moles of gas are added (Assume that the temperature and pressure are held constant)______________16.2 L 4.64 L 12.9 L 3.82 L Calculate the volume of 0.222 moles of gas at a pressure of 1.30 atm and a temperature of 298 K.__________0.0509 L 4.18 L 0.239 L 86.0 L A sample of NO_2 gas has a density of 2.25 g middot L^-1 at 277 K. What is the pressure of the gas, in bar? [R = 0.0831447 L middot bar middot mol^-1 middot K^-1]___________2.22 bar 1.11 bar 1.13 bar 0 901 bar A gas mixture has a total pressure of 774 Torr. The mixture contains 56.0 Torr O_2, 145 Torr N_2, 322 Torr He, and some fluorine gas. What is the mole fraction of the oxygen gas in this mixture?_________________0.187 0.416 0.324 0.0724

Explanation / Answer

9.

Basis : 100 gm of HClO4 solution

Mass of HClO4= 79.5%, mass of HClO4= 79.5 gms

Molecular weight of HClO4= 1+35.5+64=100.5

Moles= mass/Molecular weight

Moles of HClO4= 79.5/100.5=0.79

Mass of water= 29.5 gm, moles of water=29.5/18=1.64moles

Total moles of mixture= Moles of water+ Moles of HClO4

= 0.79+1.64 = 2.43

Volume of the mixture= Mass/Density = 100/1.67 ml =59.88 ml=59.88/1000L=0.05988L

Molarity= moles of solute (HClO4/ L of solution = 0.79/0.05988= 13.21 ( Closest answer is 12.5)

10.

101325 Pa= 1atm

0.3Pa= 0.3/101325 atm=3*10-6 atm ( correct answer is C)

11.

Gas law states that P1V1/T1= P2V2/T2

At constant temperature, T1=T2

1.2*44.4= 0.8*V2

V2= 1.2*44.4/0.8=67ml ( B is correct)

12.

At Constant pressure , V1/T1= V2/T2

and hence T1= V1*T2/V2= 3.8*(-5.6+273.15)/1.12=909 deg.c ( D is correct)

13.

From from PV= nRT

V1/n1= V2/n2 ( When P, T are constant)

8.27/0.333= V2/(0.187+0.333)= V2/0.52

V2= 8.27*0.52/0.333=12.91 L ( C is correct )

14.

From PV= nRT, V= nRT/P= 0.222*0.0821*298/1.3 =4.18 L ( B is correct)

15.

From PV= nRT

PV= (mass/Molecular weight)*RT

P* Molecular weight= (mass/Volume)*RT

P*46= 2.25*0.0831447*277

P= 2.25*0.0831447*277/46

=1.13 bar

16.

Partial pressure of Oxygen= Mole fraction * Total pressure

Mole fraction of oxygen= 56/774=0.0724 ( D is correct)

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