Acids, Bases, and Solutions

Solution A solution is a homogeneous mixture. It is made by dissolving a solute in a solvent. Solvent dissolves solute. Water dissolves salt. Water is the solvent, salt is the solute.

Concentration A measurement of the amount of solute that is dissolved in a given solvent. Solvent dissolves solute. Ways of expressing concentration Molarity (M) = moles solute / liters solution Molality (m) = moles solute / kg solvent

Example What is the molarity of a solution when 3 moles of NaOH are dissolved in 6 liters of solution? Molarity = moles solute / liter sol’n = 3 moles NaOH / 6 L sol’n = 0.5 M NaOH What is the molarity of a solution when 20 grams of NaOH are dissolved in 5 liters of solution? 20 grams NaOH = 0.5 moles = 0.5 moles / 5 L sol’n = 0.1 M NaOH

Now you try What is the molarity of a solution created by adding 48 grams of lithium hydroxide to enough water to make 3 liters of solution? Answer: 0.67 M LiOH What is the molarity of a solution created by adding 18 grams of hydrochloric acid to enough water to make 2 liters of solution? Answer: 0.25 M HCl

More How many grams of potassium hydroxide are required to make 8 liters of a 0.3 M potassium hydroxide solution? 134.4 grams KOH How many milliliters of a 1.2 M sulfuric acid solution can be made with 9.8 grams of sulfuric acid? 83.3 mL

More How many grams of calcium hydroxide is in 95 milliliters of a 0.5 M calcium hydroxide solution? 3.515 How many liters of solution is needed to make a 0.1 M hydrobromic acid solution with 88 grams of hydrobromic acid? 10.9

More What is the molality of a solution created by adding 58 grams of magnesium hydroxide to 4 liters of water? Answer: 0.25 m Mg(OH)2 What is the molality of a solution created by adding 49 grams of sulfuric acid to 3 liters of water? Answer: 0.167 m H2SO4

Calculating Ion Concentration Write the dissociation equation. Determine the concentration of the solution. Use dimensional analysis and stoichiometry to determine ion concentration. Example: What is the hydrogen ion concentration if 2 moles of sulfuric acid are dissolved in 6 liters of solution? H2SO4 → 2H+ + SO42- 2 moles H2SO4 2 moles H+ = 0.67 M [H+] 6 L sol’n 1 moles H2SO4

Now you try What is the hydrogen ion concentration of a 3 liter solution with 24.5 grams of phosphoric acid? 0.25 M [H+] What is the hydroxide ion concentration of a 5 liter solution with 7.4 grams of calcium hydroxide? 0.04 M [OH-]

You try What is the hydrogen ion concentration of a 0.2 molar phosphoric acid solution? Answer: 0.6 M [H+] What is the hydroxide ion concentration of a solution made by adding 34 grams of calcium hydroxide to enough water to make 2 liters of solution? 0.5 M [OH-]

Acids and Bases Acids produce hydrogen ions when dissolved in water. HCl → H+ + Cl- Have a pH less than 7. Bases produce hydroxide ions when dissolved in water. Ca(OH)2 → Ca2+ + 2OH- Have a pH greater than 7 Pure water is neutral with a pH of 7

pH scale Scale used to show hydrogen ion concentration [H+] in a solution. pH scale ranges from 0-14. pH < 7 acidic pH > 7 basic pH = 7 neutral pH = -log [H+]

You Try Calculate the pH of the following hydrogen ion concentrations. 0.01 M [H+] 0.006 M [H+] 0.4 M [H+] 0.00008 M [H+]

More Calculate the pH of a 250 mL solution with 7.3 grams of hydrochloric acid. pH = 0.10 Calculate the pH of a 475 mL solution with 19.6 grams of sulfuric acid solution. pH = 0.075 Calculate the pH of a 1.6 Liter solution with 49 grams of phosphoric acid. pH = 0.028

pOH scale Scale used to show hydroxide ion concentration [OH-] in a solution. pOH scale ranges from 0-14. pOH > 7 acidic pOH < 7 basic pOH = 7 neutral pOH = -log [OH-] pH + pOH = 14 [OH-] = 10-pOH [H+] x [OH-] = 1 x 10-14

Practice What is the pOH of a 5 Liter solution with 148 grams calcium hydroxide solution? pOH = 0.10 basic What is the pOH of a 375 mL solution with .0316 grams of aluminum hydroxide? Is this solution acidic or basic? pOH = 2.50 basic What is the pH of a 50 mL solution with 0.00114 grams of magnesium hydroxide? Is this solution acidic or basic? pH = 10.9 basic