Answer to Question #177846 in Physical Chemistry for gas up

Question

A gas has a solubility in water of 11.9 g/L at 15°C and 505 kPa of pressure. What is the pressure of the gas, in atm., (at the same temperature) if the solubility of the gas is 20 mg/L?

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734 grams of lithium sulfate are dissolved to make 2500.0 mL of solution. What is the Molarity of this Solution

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Describe the process you would follow to prepare 120 ml of a 2.0 M solution of HCl if you started with a 6.0 M stock solution.

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What is the percent (mass/volume) if 12 g of KCl is added to 50 mL of water to make 93 mL of solution?

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If 75 g. of Potassium Chloride (ionic compound) is dissolved in 250 grams of water, what will be the freezing point of the solution? Kf = 1.86

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The vapor pressure of pure water is 3.17 kPa. What will be the vapor pressure of a solution containing 13 g. of potassium permanganate (KMnO4) and 750 g of water?

Answer 1

1. P₁= 505Kpa= 505000Pa= 4.98atm

m₁= 11.9g/L

T₁=288K

P₂=?

m₂=20mg/L

From ideal gas equation

PV= nRT

PV= m/M x RT

We can see that P is directly proportional to mass concentration, so we can set the equation

P₁/m₁=P₂/m₂

P₂=P₁m₂/m₁=4.98x20/11.9=8.37g/L

2. Molar mass of Li₂SO₄=110g/mol

V=2500ml=2.5L

m=734g

Mole= mass/molar mass=734/110=6.67mol

Molarity= moles/litres= 6.67/2.5=2.67M

3. C₁= 6.0M

V₁= ?

C₂= 2.0M

V₂= 120ml

C₁V₁=C₂V₂

V₁= C₂V₂/C₁= 2.0x120/6.0= 40ml

To prepare this dilute solution, pipette 40ml of the concentrated HCl into a standard flask and make it up to 1Liter.

4. %w/V= 12g/50ml x 100%=24%w/V

5. Mass of KCl= 75g

Moles of KCl= mass/molar mass= 75/74.5=1.007mol

Mass of water= 250g= 0.25Kg

Molality= moles of solute/Kg of solvent

Molality= 1.007/0.25= 4.03M

It follows that

∆T= MK_f

Where ∆T is the boiling point

∆T= 4.03x1.86=7.49°C

6. Vapour pressure of pure water P_i= 3.17Kpa

Mass of water= 750g

Mole of water= 750/18= 41.7mol

Mass of KMnO4= 13g

Molar mass of KMNO4= 158g/mol

Mole of KMnO4= 13/158= 0.082mol

Mole fraction of water, X_i= 41.7/(41.7+0.082) = 0.998

Pressure of solution, P_s= ?

From Raoult's law

P_i=X_iP_s

P_s= P_i/X_i= 3.17/0.998= 3.176KPa