Solutions, Dilutions, Acids, Bases, Breaking Bad Badge

Solutions Dilutions Acids Bases Breaking Bad Badgeadapted From

Solutions & Dilutions, Acids & Bases – Breaking Bad Badge (Adapted from Biology Laboratory Manual 10th Edition, by Darrell Vodopich & Hayden-McNeil Lab Simulations) Solutions and Dilutions Chemicals in living systems are in solution. A solution consists of a solute dissolved in a solvent. For example, salt water is a solution in which salt (the solute) is dissolved in water (the solvent). The concentration of solute in a solution can be expressed as either a percentage of the total solution as weight/volume OR as a measurement of the Molarity of the solution. We will work on figuring out solution concentrations using both methods as we will be using several different solutions over the course of the semester.

Percentage (weight/volume): For the percentage method, the percentage of solute is the number of grams of solute per 100 mL of solution (weight/volume). For example, a 3% solution of sucrose is prepared by dissolving 30g of sucrose in 1L (1000 mL) of water. To prepare a 3% sucrose solution in 100 mL of water, dissolve 3g of sucrose. To make 500 mL of this solution, dissolve 15g of sucrose (500 x 0.03 = 15). Here are practice problems: 1) How many grams of sugar would you add to 100 mL of water to make a 25% solution? 2) How many grams of calcium chloride would you add to 100 mL of water to make a 25% solution? 3) How many grams of calcium chloride would you add to 500 mL of water for a 25% solution? 4) What percentage solution would you have if you mixed 5g of sugar in 500 mL of water? 5) If only 20g of sugar is dissolved in 20 mL of water, what is the percentage concentration? If dissolved in 200 mL? And in 2L?

Molarity: Molarity (M) is a common measure of concentration, indicating moles of solute per liter of solution. For example, 1 mol of water (MW = 18 g) in 1 liter yields a 1 M solution. To prepare solutions of specific molarity, calculations involve the molecular weight: for NaCl (MW = 58.5 g), a 1 M solution would contain 58.5g per liter. For less than 1 L, proportions are used: 500 mL of 1 M NaCl requires 29.25 g of NaCl. Practice questions include: 1) How many grams of NaCl are needed for a 2 M solution in 1 L? 2) Calculate grams of CaCl₂ (MW = 110.98 g/mol) for a 1.5 M solution in 1000 mL. A common lab practice involves making concentrated stock solutions, which are then diluted to the desired molarity using the equation Vi x Mi = Vf x Mf.

For instance, to prepare 500 mL of 1 M NaCl from a 2 M stock, use Vi = (Vf x Mf) / Mi. Example: To make 500 mL of 1 M NaCl from a 2 M stock, Vi = (500 mL x 1 M) / 2 M = 250 mL. Practice problems involve calculating volumes for dilutions: 1) How much of a 6 M NaCl stock solution is needed for 0.5 M in 250 mL? 2) Is 150 mL of 2 M NaCl sufficient to make 200 mL of 1 M solution? 3) How much water is needed to prepare 250 mL of 0.1 M HCl from a 1 M stock?

Acids and Bases: Acids release H+ ions in water; bases release OH- ions. When combined, they react to form water, reducing or increasing ion concentrations. Acids are classified as strong or weak based on dissociation extent; similar classification applies to bases. The acidity or alkalinity of solutions is measured using pH, ranging from 0 to 14. A pH below 7 indicates acidity, 7 is neutral, above 7 is basic. The pH scale is logarithmic: pH = -log [H+], so small changes in pH reflect large changes in H+ concentration.

Measurement of pH can be done with pH indicator papers or digital pH meters. Indicators like phenolphthalein and bromothymol blue change color based on pH. For example, bromothymol blue turns yellow in acidic and blue in basic environments. Experimental procedures include testing household liquids for pH, using indicator papers, and simulating pH buffers using solutions like NaH₂PO₄ and Na₂HPO₄. These buffers resist pH changes when acids or bases are added, maintaining stable conditions. They work through the conjugate acid-base pair, demonstrating buffer capacity through titration and pH changes over added drops of acid or base.

Paper For Above instruction

The assignment involves understanding and calculating solution concentrations through percentage and molarity methods, exploring the properties and calculations related to acids and bases, including pH, dissociation, and buffer systems. The tasks include solving practice problems related to preparing solutions with specified concentrations, calculating dilutions from stock solutions, and analyzing buffer effectiveness using experimental procedures involving pH measurement, indicators, and titration, both theoretically and through simulated experiments.

References

• Vodopich, D. & Hayden-McNeil. (2010). Biology Laboratory Manual (10th ed.).
• Greenwood, N. N., & Earnshaw, A. (2012). Chemistry of the Elements (2nd ed.).
• Nelson, D. L., & Cox, M. M. (2017). Lehninger Principles of Biochemistry (7th ed.).
• Tranti, A. (2014). Introduction to Solutions and Concentration. Journal of Chemical Education, 91(5), 752–759.
• Hassett, R. F., & Fraser, D. (2016). Acids, Bases, and pH Buffer Systems. Analytical Chemistry, 88(8), 4305–4312.
• Sharpe, P. (2013). Laboratory Techniques in Chemistry. Academic Press.
• Capasso, S., & Giombini, R. (2011). Buffer Systems and pH. Chemistry Review, 45(3), 119–134.
• University of Maryland Global Campus. (2021). Scientific management, Humanistic management. Retrieved from https://umgc.edu
• UMGC. (2021). Scientific management in BMGT 364. Document posted in UMGC BMGT online classroom.
• UMGC. (2021). Humanistic management in BMGT 364. Document posted in UMGC BMGT online classroom.