Expression of concentration of solutions of solids in liquids

A diluted or concentrated solution; this is a qualitative means of expressing the solution’s concentration. A dilute solution contains a small amount of solute, whereas a concentrated solution contains a big amount of solute. However, these are relative phrases that do not provide us with the solution’s quantitative concentration.

Concentration

It refers to the amount of solute in a litre of solution. It is signified by the letters C.

C=Solute’s weight in grams / volume in litres

1. Parts Per Million (ppm)

Abbreviation of parts per million, ppm is the amount of a chemical in relation to the substance that contains it. Example is that Lead levels in the water were above 3,500 ppm.

ppm(B)= (B’s mass in the solution / Total mass of the solution)×106

2. Mass Percentage (w/w):

It’s called mass percentage (w/w) when the concentration is reported as a percentage of one component in the solution by mass. If we have a solution with component B as the solute and component C as the solvent, the mass percentage is:

B’s mass % = ( B’s mass /  Total mass of the solution) ×100

3. Volume Percentage (V/V):

The concentration is sometimes expressed as a percent of one component in the solution by volume, which is known as volume percentage and written as:

B’s volume % = (Component’s Volume of  B / Total volume of the solution) ×100

4. Percentage of mass by volume (w/V):

The pharmaceutical sector makes extensive use of this unit. It’s the mass of a dissolved solute per 100 millilitres of solution. Example:- 0.9 percent (w/v) KCl solution containing 0.9 g of KCl per 100 mL of solution in medical saline solutions.

5. Molarity (M):

Molarity is one of the most widely used ways for expressing concentrations. It refers to the number of moles of solute dissolved in a litre of solution. If an ethanol solution is designated 0.25 M, it signifies that 0.25 moles of ethanol are dissolved in one litre of the solution. Formula:-

Molarity= mass / (volume × molar mass)

6. Molality (m):

Molality refers to the relationship between the number of moles of solute and the mass of the solvent. It’s measured in moles of dissolved solute per kilogramme of solvent. The following is the molality formula:

Molality(m)= Solute’s mass / Solvent’s mass in kg

7. Normality

Normality of a solution is calculated as the amount of gram or mole equivalent of solute in one litre of solution.

N= (Solute’s weight in grams) / (Equivalent mass × Volume in L)

Normality and molarity have a relationship.

• Molarity x Molar Mass = Normality x Equivalent Wt.
• Molarity x Valency = Normality
• Molarity x  number of H+ or OH– ions = Normality

8. Formality

In 1 L of solution, amount of formula mass of solute present in solution is known as Formality. The letter F stands for it.

F=(Weight of solute in gram) / (Formula wt×Volume in liter)

• It works in the case of ionic solids such as NaCl.

9. Mole Fraction:

When a solution contains both a solvent and a solute, a mole fraction is the ratio of one component’s moles to the total moles in the solution. x is the symbol for it. Assume we have a solution with As as the solute and B as the solvent. Let nA and nB represent the number of moles of A and B, respectively, in the solution. As a result, the mole fractions of A and B are:

xA=nA/nA+nB

xB=nB/nA+nB

The methods for expressing the concentration of solutions discussed above are widely utilised. All of the methods describe the same thing: the concentration of a solution, but each has its own set of benefits and drawbacks. Molarity is temperature dependent, whereas mole fraction and molality are temperature independent. All of these approaches are used to express concentrations, which is a prerequisite.

Solutions of Solids in Liquids

1. A saturated solution is one that has an excess of solute and is still in touch with it.
2. The solubility of a solute is defined as the amount of solute dissolved in 100g of solvent in a saturated solution at a certain temperature.
3. Solubility is inversely related to temperature for exothermic compounds as KOH, CaO, Ca(OH)2, M2CO3, M2SO4, and so on.
4. Solubility is directly proportional to temperature for endothermic compounds like NaCl, KNO3, NaNO3, glucose, and so on.

Gases’ Solubility

The absorption coefficient,k, which is the volume of gas dissolved per unit volume of solvent at 1 atm pressure and a certain temperature, is the most common way of expressing the solubility of gases.

The solubility of a gas in a liquid is determined by several factors.

• Temperature:- Because most gas dissolving is exothermic, temperature solubility is inversely related to temperature.
• Gas nature :- Gases with a stronger van der Waals force of attraction, or gases that are easier to liquefy, are more soluble. SO2 and CO2, for example, are more water soluble than O2, N2, and H2.
• The nature of the solvent :— Gases that may ionise in an aqueous solution are more stable in water than in other solvents.

Conclusion

The concentration of a solution lets us figure out how fast particles in a molecule or compound collide.The concentration of the solution also aids in determining the amount of solute and solvent. A dilute solution contains a small amount of solute, whereas a concentrated solution contains a big amount of solute. However, these are relative phrases that do not provide us with the solution’s quantitative concentration.