The equation for Molarity must be rearranged to solve for the moles of solute (Na Cl).
The moles of solute can then be converted into grams.
Typically in a laboratory setting such as ones in an academic setting, it isn’t uncommon to work with volumes of solvent less than a litre for health and safety reasons and to curtail costs.
In such cases, known amounts of chemical substance are dissolved in volumes lower than one litre and the concentration is generally expressed in molarity (M or mol/L). We will now go through some examples to try and help you understand how to calculate the molarity and how to do calculations to do with molarity.
To get around this problem chemists commonly make up their solutions in volumetric flasks.
Solving Molarity Problems
These are flasks that have a long neck with an etched line indicating the volume.The solute is defined as the substance being dissolved, while the solvent is the substance where the solute is dissolved (usually water).The solution is the combination of the solute and the solvent.An aqueous solution consists of at least two components, the solvent (water) and the solute (the stuff dissolved in the water).Usually one wants to keep track of the amount of the solute dissolved in the solution. One could do by keeping track of the concentration by determining the mass of each component, but it is usually easier to measure liquids by volume instead of mass.Recall the relationship between mass, moles and molecular weight. However, we are given the mass rather than the number of moles.We were given the volume of solvent and the mass and molecular weight of cis-(−)-carveol. For this reason, we will need to convert mass to moles using one of the formulas shown in the previous article. All the formulas that we need to solve this problem requires the mass and the volume in grams (g) in litres (l), respectively. Converting mass to moles: Use Formula 1: Answer to Problem 3: Using 2200 mg of substance dissolved in 20 ml of solvent, the trainee prepared a solution of cis-(−)-carveol with a concentration of 0.725 mol/L for polarimetry studies.Following on the previous article in this series, we will now turn our attention on one of the most common ways of expressing the concentration – using molarity.Molarity, sometimes referred to as molar concentration, is defined as the concentration of a substance in solution, expressed as the number moles of solute per litre of solution.To do this measure called molarity is commonly used.Molarity (M) is defined as the number of moles of solute (n) divided by the volume (V) of the solution in liters.