CHM110H5 Lecture Notes - Lecture 1: Molality, Molar Concentration

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1 Oct 2015

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Molarity and molality are both different measurements of the concentration of the solution. They both are ratios that are either moles to volume of solution or moles to mass of solution. Molarity is the moles of solute per volume of the solution1. The volume measured is the volume of the solution in total, not just the volume of the solvent2. This volume of the solution can either contain more than or less than one litre of solvent due to the process of dissociation which causes the volume of the solution to increase or decrease4. Since molarity depends on the volume of the solution, it is slightly affected by temperature1. Molality is the ratio of moles to the mass of the solvent1. Chemical reactions are measured in proportions of not, not volume. This is because volume has the ability to vary under different temperature and pressure3.

Related Questions

1. Letâs separate the different data pieces of the HNO3 solution into solute, solvent and solution. Using the density of nitric acid solution (1.09 g/mL) and the molarity you calculated above (0.1532M) and the volume used (14.92ml), calculate the following in the table below.

Volume of original nitric acid solution: _______________

Grams & Moles of Nitric Acid? ___________________

Grams of Water? ________________

Total Solution? __________________

In another titration, a student uses 1.023 M HCl solution to standardize a sodium hydroxide solution. Assuming 1.00 L of HCl solution and its density of 1.02 g/mL, calculate the mass percent and molality of the HCl solution.

mass percent:_________________

molality: ___________________

3. Draw the expanded structure of ethanoic acid (acetic acid) in the provided box.

4. What is the solute in the vinegar solution?

Experiment 10 Colligative Properties Introduction A pinch of wa make boiling water hotter. A handful will clear the snow from your steps. Every day we the physical properties of materials around us, but often don't know why we use these particular s or what chemistry is involved. Modifying the temperature of phase changes, by adding a second chemical to the pure solvent are examples of manipulating the Colligative Properties of a solution. this lab, we will study how varying the concentration and type of a salt affects the point of a solution. Colligative properties are properties of a solution containing 2 or more components. Typically, the primary is the solvent and the other called the such as color or hardness, properties depend on the number of particles of astute in the not the identity of the In many cases, the rokute will determine the number of solute particles (degree of ionization, solubility, etc,) in the solvent, but a colligative property does not depend upon the nature of the particles. Two colligative properties commonly encountered are boiling point elevation and freezing point depression (the temperature of of a is lower than of pure solvent). We will be studying boiling point elevation in this Most of the previous work that you have done with solutions has involved units of molarity, M, or moles of solute per liter of solution. Boiling point elevation calculations (as well as those for freezing point depression) or moles of solute per kilogram of solvent. boili change of temperature. When the temperature of a solution changes, the volume of the solution also changes. Since molarity depends on a change in wil the solution's molarity. Molality depends on the mass of the solvent. and thus is independent of temperature. n't Hoff Factor salt into and the of moles inorganic salts in an aque the based on the addition of the number dissociates, the total number of particles in the solution will be of cations and anions produced from the dissociation. Thus; Nacion Na Choaa (2moles of particles) Cacbrs Ca +2ch (3moles of particles) The quantity of particles produced per mole of solute is called the van'tHoff factor and is given the symbol, i, If 1 mole of sodium chloride were completely dissociated, iwould be 2. This theory works very well for dilute solutions and non-electrolytes (i 1, no dissociation at all since nonelectrolytes not ionize), For does not always apply to more concentrated solutions. Thus, when there are a large number of particles in a solution, they have a tendency to recombine as the salt and you don't get 100% dissociation. example, at a NaCl concentration of 0.1M, iwill be 1.81 (90% dissociation) rather than 2 (100%). Boiling Point Elevation solute causes the solution to boil at a higher When a solution is heated, the presence of a non-volatile point of the pure liquid and the temperature than the pure The difference between the boiling boiling point of the solution is: 169

Chemists often use molarity, M, in moles/liter, to measure the concentration of solutions. Molarity is a common unit of concentration because the volume of a liquid is very easy to measure. However, the drawback of using molarity is that volume is a temperature-dependent quality. As temperature changes, density changes, which affects volume. Volume markings for most laboratory glassware are calibrated for room temperature, about 20°C. Fortunately, there are several other ways of expressing concentration that do not involve volume and are therefore temperature independent.

A mass of 0.630 g of NaCl is dissolved in 525 g of water.

1. Calculate the morality of the solution.

2. Calculate the mole fraction of salt in the solution.

3. Calculate the concentration of the salt solution in percent by mass.

4. Calculate the concentration of the salt solution in parts per million.

Include units for each.

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CHM110H5 Lecture Notes - Lecture 1: Molality, Molar Concentration

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