Question

problems related to concentration of solution

Answer 1

Answer:

How to find concentration of solution?

A solution is a homogeneous mixture of two or more components in which the particle size is smaller than 1 nm. A solution concentration is a measure of the quantity of solute that has been dissolved in a given quantity of solvent or solution. One that contains a relatively high volume of dissolved solute is a concentrated solution. That that contains a relatively minimal volume of dissolved solute is a dilute solution.

Determination of concentration of solution

The concentration of the solution can be determined by the formulas listed below

Using the standard formula

It is the amount of solute present in one liter of solution. It is denoted by C or S.

Here, C or S is the concentration

m is the mass of the solute dissolved

V is the volume of the solution

Mass Percentage

When the concentration is expressed as the percent of one component in the solution by mass it is called mass percentage (w/w). Assume that a solution containing element A as the solute and B as the solvent, then its mass percentage is expressed as:

Mass % of A =

Volume Percentage (V/V):

The concentration can be expressed as a percent of one component in the solution by volume, it is then called as volume percentage and is given as:

volume% of A =

Molarity (M):

Molarity of a given solution is defined as the total number of moles of solute per litre of solution.

The equation for calculating molarity is the ratio of the moles of solute whose molarity is to be calculated and the volume of solvent used to dissolve the given solute.

Here,

M is the molality of the solution that is to be calculated

n is the number of moles of the solute

V is the volume of solution given in terms of litres

Molality (m):

Molality (m) is defined as the number of moles of solute per kilogram of solvent. The formula for molality is given as;

Molality (m) = moles of solute / kilograms of solvent

The molality formula is as given-

Normality

Normality is described as the number of gram or mole equivalents of solute present in one litre of a solution. It is the number of gram equivalents of solute present in one liter of the solution and it is denoted by N.

The relation between normality and molarity.

N x Eq.Wt = Molarity x Molar mass

N = Molarity x Valency

N = Molarity x Number of H+ or OH– ion.

Explanation:

1) 2 ml of water is added to 4 g of a powdered drug. The final volume is 3ml. Find the mass by volume percentage of the solution?

Answer Given, Mass of solute = 4gVolume of solution = 3mlMass by volume percentage = Mass of soluteVolume of solutionMass of soluteVolume of solution\frac{\text{Mass of solute}}{\text{Volume of solution}}x100 = 4g3ml4g3ml\frac{4g}{3ml} = 133%Therefore, the mass by volume percentage is 133 %.

Question 2) Many people use a solution of Na3PO4 to clean walls before putting up wallpaper. The recommended concentration is 1.7 % (m/v). Find the mass of Na3PO4 needed to make 2.0 L of the solution?

Answer 2) Given, Mass/Volume percentage = 1.7 %Volume of Solution = 2000 mlMass by volume percentage = Mass of soluteVolume of solutionMass of soluteVolume of solution\frac{\text{Mass of solute}}{\text{Volume of solution}} × 100 1.7 % = Mass of solute2000mlMass of solute2000ml\frac{\text{Mass of solute}}{2000ml} ×100Mass of solute = 34 gTherefore, the mass required is 34 g.In chemistry, we are often required to calculate the concentration of the solution. The above-mentioned methods of expressing the concentration of a solution are important. The solved examples are helpful for a better understanding of the concept of concentration of a solution.