CHEMICAL ARTICLES

CHEMICAL PROPERTIES OF SOLUTIONS

INCREASE DOWN POINT

Boiling occurs because heat increases motion or kinetic energy, from molecules that cause fluid to exist at the point where the liquid evaporates, regardless of being on the top surface or in the deepest part of the liquid

When a solution has a high vapor pressure at a certain temperature, then the molecules within the solution are easy to escape from the surface of the solution. Or it can be said that at the same temperature a solution has a low vapor pressure, then the molecule molecules in the solution can not easily escape from the solution. So a solution with a higher vapor pressure at a certain temperature will have a boiling point

The lower one. The liquid will boil when the vapor pressure becomes equal to the outside air pressure. Liquid boiling point at air pressure 760 mmHg is called the standard boiling point or normal boiling point. So what is meant by the boiling point is the temperature at which the saturated vapor pressure of the liquid is equal to the outside air pressure (pressure on the liquid surface).

The difference in the boiling point of a solution with a solvent boiling point is called an increase in the boiling point (ΔTb)

ΔTb = boiling point of solution - solvent boiling point)

According to Raoult's law, the magnitude of the boiling point increase of the solution is proportional to the product of the solution molality (m) with the increase in molal boiling point (Kb). Therefore, the boiling point increase can be formulated as follows.

ΔTb = Kb ⋅ m

Information:

B ΔT = increase in molal boiling point

Kb = the increase in molal boiling point

M = molality of solution

Example

Sodium hydroxide 1.6 grams dissolved in 500 grams of water. Calculate the boiling point of the solution! (Kb water = 0,52 ° Cm-1, Ar Na = 23, Ar O = 16, Ar H = 1)

Resolution:

Given: m = 1.6 grams p = 500 grams Kb = 0,52 ° Cm-1

Asked: Tb ...?

Answer: ΔTb = m⋅ Kb

= M x 1,000 Kb NaOH

Mr p

×

= 0.04 × 2 × 0,52 ° C

= 0.0416 ° C

Td = 100 ° C + b ΔT

= 100 ° C + 0.0416 ° C

= 100.0416 ° C

Thus, the boiling point of the NaOH solution is 100.0416 ° C.

BREAKFAST STATES (ΛTf)

The freezing point drop in the concept is similar to the boiling point increase. The solution has a lower freezing point

Compared with pure solvent.

The difference between the freezing point of the solvent and the freezing point of the solution is called the decrease of the freezing point of the solution (ΔTf = freezing point).

 ΔTf = Freezing point of solvent - freezing point of solution

According to Raoult's law the decrease of freezing point of the solution is formulated as follows.

ΔTf = m ⋅ Kf

Information:

F ΔT = decrease in freezing point, m = solution molality, Kf = the molecular frost rate decrease

OSMOSIS PRESSURE

Sometimes a patient in the hospital should be given intravenous fluids. Actually what is the infusion fluid? The solution inserted into the patient's body through a blood vessel must have the same pressure as the pressure of the blood cells. If the infusion fluid pressure is higher then the infusion fluid will come out of the blood cells. The working principle of this infusion is essentially osmotic pressure. The pressure here is the pressure that must be applied to a solution to prevent the entry of solute molecules through a semipermeable membrane from pure solvent to solution.

Actually what is osmosis? The pure liquid or dilute solution will move through the membrane or obstacle to

To reach a more concentrated solution. This is called osmosis. These membranes or obstructions are called membranes

Semipermiabel.

Osmotic pressure is included in the colligative properties because the magnitude depends only on the amount of solute particles.

J.H. Vant Hoff found a relationship between the osmotic pressure of dilute solutions with the ideal gas equation, which is

Written as follows:

     Π V = nRT

Description: π = osmotic pressure, V = volume of solution (L), n = number of moles of solute, R = gas constant (0.082 L atm mol-1K-1) T = absolute temperature (K)

Equations can also be written as follows.

Π = n RT

Remember that n / V is the solubility of solution (M), so the equation can be changed to π = MRT

Example A patient needs a glucose infusion solution. When the volume of the fluid is 0.3 molar at 37 ° C,

Determine the osmotic pressure! (R = 0.082 L atm mol-1K-1)

Resolution:

Given: M = 0.3 mol L-1

T = 37 ° C + 273 = 310 K

R = 0.082 L atm mol-1K-1

Asked: π ...?

Answer: π = 0.3 mol L-1 × 0.082 L atm mol-1K-1 × 310 K

= 7,626 L

CHEMICAL PROPERTIES OF ELECTROLYING SOLUTIONS

Did you know that the solution consists of an electrolyte solution and a nonelectrolyte solution. Electrolyte solution is a solution that can conduct electrical current. The colligative nature of the nonelectrolyte solution we have learned in the future, what about the colligative nature of the electrolyte solution? The electrolyte solution has a greater colligative property than nonelectrolyte, that the decrease of freezing point of NaCl is greater than that of glucose. The price comparison of the colligative properties of an electrolyte solution with a nonelectrolyte solution is called Van't Hoff factor and is denoted by i.

So for electrolyte solution apply the formula:

1. ΔP = XA × P × i

2. ΔTb = K × m × i

3. f ΔTf = K × m × i

4. π = M × R × T × i

I = van factor, t hoff = 1 + (n - 1) α

N = number of ions, α = degrees of ionization

Problems example;

At 37 ° C into water dissolved 1.71 grams Ba (OH) 2 So the volume of 100 mL (Mr. Ba (OH) 2 = 171). Count big

Osmotic pressure! (R = 0.082 L atm mol-1K-1)

Resolution:

Known: m = 1.71 grams

V = 100 mL = 0.1 L

Mr. Ba (OH) 2 = 171

R = 0.082 L atm mol-1K-1

T = 37 ° C = 310 K

Asked: π ...?

Answer: Ba (OH) 2 is an electrolyte.

Ba (OH) 2 → Ba2 + + 2 OH¯, n = 3

Mol Ba (OH) 2 = gram / Mr

= 1.71 grams

171

= 0.01 mol

M = n / V = ​​0.01 mol / 0.1 L = 0.1 mol ⋅ L-1

Π = M × R × T × i

= 0.1 mol L-1 × 0.082 L atm mol-1K-1

× 310 K × (1 + (3 - 1) 1) = 7,626 atm