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Dilution calculator and problems solver

This online calculator can calculate the molar concentration (molarity) of a solute or volume of a solution before or after the dilution.

These online calculators can help with dilution problems. Generally, in dilution problems you either dilute a solution or mix two solutions with different concentrations. So, the first calculator below can solve dilution problems, and the second calculator below can solve mix problems. Theory and formulas can be found below the calculators.

Dilute a solution problems solver

This calculator can solve the following types of problems:

  1. Find final molarity of a solution
  2. Find final volume of a solution
  3. Find initial molarity of a solution
  4. Find initial volume of a solution

To see examples for each type of problems, change problem type in the calculator below.

PLANETCALC, Dilution calculator and problems solver

Dilution calculator and problems solver

Example problem
 
Molarity of initial solution, mol/L
 
Volume of initial solution, liters
 
Molarity of final solution, mol/L
 
Volume of final solution, liters
 
Digits after the decimal point: 2

Mix solutions problems solver

This calculator can solve the following types of problems:

  1. Find molarity of final solution
  2. Find volume of final solution
  3. Find molarity of one of the starting solutions

To see examples for each type of problems, change problem type in the calculator below.

PLANETCALC, Mixed solutions calculator and problems solver

Mixed solutions calculator and problems solver

Example problem
 

First starting solution

Second starting solution

Final solution

Molarity of final solution, mol/L
 
Volume of final solution
 
Molarity of second starting solution, mol/L
 
Digits after the decimal point: 2

Dilution and molarity

Dilution is the process of decreasing the concentration of a solute in a solution, usually simply by mixing with more solvent like adding more water to a solution. To dilute a solution means to add more solvent without the addition of more solute. The resulting solution is thoroughly mixed so as to ensure that all parts of the solution are identical.

Solution concentration is described with molarity (or molar concentration), which is the number of moles of solute per liter of solution, measured in mol/liter, denoted as M, and calculated as follows

M=\frac{\text{mol solute}}{\text{L of solution}}

which can be rearranged like this

M \cdot \text{L of solution}=\text{mol solute}

The key to problem solving is the understanding that after dilution we still have the same amount of solute in moles. If we denote starting molarity as M_s, starting volume as V_s, final molarity as M_f and final volume as V_f, we can write

M_s \cdot V_s=\text{mol solute}=M_f \cdot V_f,

which gives us the following proportion

M_s \cdot V_s=M_f \cdot V_f,

This equation is used in first calculator. For example, to find final molarity, you simply use

M_f =\frac{M_s \cdot V_s}{V_f}

The same logic can be applied to the mix problems. Of course we assume that the problems are about the mixing of the same solute, and there is no volume contraction upon mixing.

Thus, the equation look like follows:

M_{s_1} \cdot V_{s_1} + M_{s_2} \cdot V_{s_2}=M_f \cdot V_f, and

V_{s_1} + V_{s_2}= V_f

where s_1 and s_2 denotes two different starting solutions.

From these equations it is easy to find final values or unknown concentration of one of the starting solutions.

Sometimes dilution problem gives amounts of solute in grams. In this case, you need to know the chemical formula of the solute and then convert the mass of solute to the amount of moles or find molarity. You can use Molar mass of the substance and Molarity calculator for this.

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