The key difference between a 1.0 molar solution and a 1 molal solution is that a 1.0 molar solution has one mole of solute dissolved in the solution whereas a 1 molal solution has one mole of solutes dissolved in one kilogram of solution.
Long ago, Avogadro hypothesized that there is a specific number that represents the number of atoms or molecules in one mole of a substance. Thus, one mole of each element contains an equal number of atoms, irrespective of the atomic weight of that element. As a result, the concepts of molarity and molality were also developed to describe concentrations of a solute in a solution. While molarity is the measure of a number of moles of the solute in a litre of solution, molality is the number of moles in 1kg of the solution. Hence, it is easy to find out the difference between a 1.0 molar solution and a 1 molal solution.
CONTENTS
1. Overview and Key Difference
2. What is a 1.0 Molar Solution
3. What is a 1 Molal Solution
4. Side by Side Comparison – a 1.0 Molar Solution vs a 1 Molal Solution in Tabular Form
5. Summary
What is a 1.0 Molar Solution?
A 1.0 molar solution is a solution that contains one mole of a solute dissolved in a litre of solution. Furthermore, this is a term of concentration, and we call it the “molarity” of the solution.
Figure 01: Different Solutions have different Molarities and Molalities
The symbol for this term is “M”. the unit of measurement is mol/L. For example, an aqueous 1.0 molar solution of NaCl (sodium chloride) means a solution of sodium chloride containing one mole of NaCl dissolved in a litre of water.
What is a 1 Molal Solution?
A 1 molal solution is a solution that contains one mole of a solute dissolved in a kilogram of a solution. Hence, the unit of measurement is mol/kg.
Figure 02: A 1 Molal Solution of Aqueous Sodium Chloride Solution contains one mole of NaCl in one kilogram of Water.
Moreover, this is also a term of concentration that we name as the “molality” of the solution. We can denote by “m”. For example, a 1 molal solution of sodium chloride means an aqueous solution of NaCl containing one mole NaCl dissolved in a kilogram of water.
What is the Difference Between a 1.0 Molar Solution and a 1 Molal Solution?
A 1.0 molar solution is a solution that contains one mole of a solute dissolved in a litre of solution whereas A 1 molal solution is a solution that contains one mole of a solute dissolved in a kilogram of a solution. Therefore, this is the key difference between a 1.0 molar and a 1 molal solution. Furthermore, the unit of measurement of 1.0 molar solution is mol/L while that of 1 molal solution is mol/kg. However, if water is the solvent, there is not much of a difference between a 1.0 molar solution and a 1 molal solution. It is because, at room temperature, the density of water is taken to be 1 kg/L. Therefore, this results in molarity and molality of solutions to be equal.
Summary – a 1.0 Molar Solution vs a 1 Molal Solution
Molarity and molality are very important terms in chemistry that we use to measure the concentration of a solution. The key difference between a 1.0 molar solution and a 1 molal solution is that a 1.0 molar solution has one mole of solute dissolved in the solution. Whereas, a 1 molal solution has one mole of solutes dissolved in one kilogram of solution.
Reference:
1. “Molar Concentration.” Wikipedia, Wikimedia Foundation, 17 Oct. 2018. Available here
2. Mott, Vallerie. “Introduction to Chemistry.” Lumen. Available here
Image Courtesy:
1.”chemistry-liquid-glass-research-laboratory-medicine” (CC0) via pixnio
2.”SaltInWaterSolutionLiquid”By Chris 73 / Wikimedia Commons, (CC BY-SA 3.0) via Commons Wikimedia