Calculating molarity and molality with examples

Molarity

First, molarity or molar concentration is defined as the concentration of a solution in moles per dm3 or 1L. that is still referring to the same amount of volume of a substance. Taking sodium hydroxide as a example. The molar mass of NaOH is 40g. Therefore, a molar solution of sodium hydroxide contains 1 mole or 40g of the hydroxide in 1 dm3 of the solution.

Molar mass of any substance is the mass of one mole of that substance expressed in grams.

Mass concentration is said to be the product of molarity and molar mass. It also mean the concentration of a solution in g/dm3. Hence, mass concentration also helps in calculating molarity.

Solute is any substance that dissolve in a solvent to make a solution.

Solvent is a substance that dissolves a solute to make a solution.

let discuss on calculating molarity and molality today. visit our site for more.

Molality

It’s also similar to molarity. But the difference is listed as follows:

• Unit for molality is lowercase (m). Therfore, on the other hand, unit for molarity is written as uppercase (M).
• molarity is the ratio of moles to volume of solution in litre or dm3. Hence, molality is the ratio of moles to mass of solvent in kilogram.

Formulas for calculating molarity based questions

Let quickly look at all formulas you can use while calculating molarity based questions. although calculating molarity and molality is quite easy right? Note, M stands for molarity.

• M = no mole of solute / volume of solution
• Molarity = mass concentration / molar mass
• M = mass / molar mass x 1000 / volume of solution in ml or cm3
• CA xVA / CB x VB =NA/NB
• C1 X V1 = C2 x C2

Formulas for calculating molality based questions

Let quickly look at this few formulas we can use while calculating molality based questions. Note, m stands for molality.

• m = mole of solute / mass of solvent in kilogram
• m = mass of solute / molar mass of solute x 1/kg of solvent

Examples involving molarity

Let take a look a this few examples for better understanding on what molarity is all about.

• 1. 15g of NaBr is dissolved in 400ml of solution. what is the molarity?.

• 2. A dilute H2SO4, B contains 1.5g of NaOH per 250cm3 of solution. 25cm3 of B requires 15.5cm3 of A for complete neutralization. Calculate molarity. Tips – (1)write and balance the equation first (2) calculate mass concentration. (3)Then go on with the M.

Examples involving Molality

1. 10g of NaOH is dissolve in 500g of water. What is the molality of the solution. Tips – (1) identify solute and solution. (2) convert 500g to kg. (3) calculate the number of mole of solute.

in conclusion, i would say, "there is just a slight difference between molality and molarity." as explained in the post. leave a comment below for more.