#### What quantity (in mL) of a 45% acid solution of a monoprotic strong acid must be mixed with a 20% solution of the same acid to produce 800 mL of a 29.875% acid solution? Option: 1 320 Option: 2 325 Option: 3 316 Option: 4 330

Reactions in Solutions -

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

Mole Fraction:
It is the ratio of moles of one component to the total number of moles present In the solution. It is expressed by X for example, for a binary solution with two components A and B.

Here nA and nB represent moles of solvent and solute respectively. Mole fraction does not depend upon temperature as both solute and solvent are expressed by weight.

Molarity:
It is the number of moles or gram moles of solute dissolved per litre of the solution. Molarity is denoted by 'M'.

• When molarity of a solution is one, it is called a molar solution and when it is 0.1, solution is called decimolar solution.
•  Molarity depends upon temperature and its unit is mol/litre.
M1V1 = M2V2
• On dilution water added = V2 - V1
• When the solution of two different substances react together then

Here M, V, n are molarity, volume and number of molecules taking part in a reaction respectively.
• When a mixture of different solutions having different concentrations are taken the molarity of the mixture is calculated as follows:
• When density and % by weight of a substance in a solution are given, molarity is find as follows:

Here d = density

Molality
It is the number of moles or gram moles of solute dissolved per kilogram of the solvent. It is denoted by 'm'.

• If molality is one solution, it is called molal solution.
• One molal solution is less than one molar solution.
• Molality is preferred over molarity during experiments as molality is temperature independent while molarity is temperature-dependent.

Normality
It is the number of gram equivalents of solute present in one litre of the solution and it is denoted by 'N'.

• When normality of a solution is one, the solution is called normal solution and when it is 0.1, the solution is called deci-normal solution.

Normality Equation:

• Volume Of water added = V2 - V1
Here V2 = volume after dilution
V1 = volume before dilution
• When density and % by weight of a substance in a solution are given, normality is find as follows:

Here d = density of solution
• When a mixture of different solutions having different concentrations are taken the normality of the mixture is calculated as follows:

• In case of acid-base neutralization the normality of the resulting solution

• To find weight of substance

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

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As we have learnt,

Therefore, Option (3) is correct