Biochemical Calculations Biochemistry Department Faculty of Science University

Biochemical Calculations Biochemistry Department, Faculty of Science University of Tabuk

Molarity (M) �Another way of expressing concentration is called molarity. �Molarity is the number of moles of solute dissolved in one liter of solution. �The units, therefore are moles per liter, specifically it's moles of solute per liter of solution.

Molarity (M) �Molarity = moles of solute liter of solution �Molarity is abbreviated as M or M. M = wt X 1000 MW X Vml

Normality (N) �Used to compare solutions on the basis of concentration of specific ions or the amount of charge that the ions have. �No. of equivalent weight per liter of solution. �Eq. wt = molecular weight (MW) Valance

Normality (N) �Normality �N = is abbreviated to (N). wt X 1000 Eq. wt X Vml

Problems To Solve: � 1 - How many grams of glucose are needed to make 100 ml of a 0. 6 mol/l solution? (MW glucose = 180). � 2 - How can you prepare 0. 1 M Na. OH solution? � 3 - Describe the preparation of 5 L of 0. 1 M Na 2 CO 3 (MW = 105. 99) from the primary standard solid.

Percent Concentration (%) 1 -Volume percent: �It is usually used when the solution is made by mixing two liquids. �The use of % is a common way of expressing the concentration of a solution.

Percent Concentration (%) �The % can be calculated using volumes as well as weights, or even both together. �Volume percent (v/v) = volume of solute X 100 volume of solution

Example: �Rubbing alcohol is generally 70% by volume isopropyl alcohol. �This means that 100 ml of solution contains 70 ml of isopropyl alcohol. �That also means that a liter (or 1000 ml) of this solution has 700 ml of isopropyl alcohol plus enough water to bring it up a total volume of 1 liter, or 1000 ml.

Percent Concentration (%) 2 - Weight percent: �is expressing the concentration of a solution in weight percent (or mass percent). �Weight percent (w/w) = weight of solute X 100 weight of solution

Question What is the weight percent of glucose in a solution made by dissolving 4. 6 g of glucose in 145. 2 g of water?

Analysis To get weight percent we need the weight of the solute and the total weight of the solution. �Determine total weight of solution: 4. 6 g+ 145. 2 g = 149. 8 g

solution �Calculate percent: �Weight % glucose = x 100 solution = 3. 1% glucose. 4. 6 g glucose 149. 8 g

Percent Concentration (%) 3 - Weight- volume percent: �Another variation on % concentration is weight/volume percent or mass/volume percent. �This variation measures the amount of solute in grams but measures the amount of solution in milliliters.

Percent Concentration (%) �An example would be a 5 %( w/v) Na. Cl solution. �It contains 5 g of Na. Cl for every 100 m. L of solution. �Weight-Volume percent (w/v) = weight of solute X 100 volume of solution