water dissolving salt. solubility & saturation fill in handout as we go…
TRANSCRIPT
- Slide 1
- Water Dissolving Salt
- Slide 2
- Solubility & Saturation FILL IN HANDOUT AS WE GO
- Slide 3
- Solubility Solubility: maximum amount of solute that can be dissolved in a given quantity of solvent at a specific temperature. Even for very soluble substances, theres a limit to how much can be dissolved in a given amount of solvent.
- Slide 4
- Saturation Saturated solution: solution at the limit Solution has as much solute as it can dissolve at that T (temperature) If more solute is added it wont dissolve and will only precipitate out In a state of dynamic equilibrium: rate of dissolving = rate of crystallizing
- Slide 5
- Saturation Unsaturated solution: solution under the limit Solution hasnt reached the limit of how much solute it can dissolve at that T If more solute is added it will dissolve Supersaturated solution: solution above the limit Solution contains higher than saturation concentration of solute Any slight disturbance/seeding causes crystallization/precipitation of excess solute
- Slide 6
- Supersaturation needle structure Supersaturation seeding
- Slide 7
- Ex: At 20 C, solubility of NaCl (s) in water is 36g/100mL.
- Slide 8
- Saturation Concentration ([ ]): quantitative measure (a number) of how much solute is contained in an amount of solvent. Ex:
- Slide 9
- Saturation Concentrated solution: qualitative term; large amount of solute dissolved. Dilute solution: qualitative term; small amount of solute dissolved.
- Slide 10
- Q: At 20 C, KCl (s) solubility is 34g/100g of water. In the laboratory, a student mixes 45g KCl (s) with 100g of water at 20 C. A.How much KCl (s) will dissolve? ___________ B.Is the solution saturated? ___________ C.What is the mass in grams of solid KCl that wont dissolve? __________________________
- Slide 11
- Q: At 50 C, the solubility of NaNO 3(s) is 114g/100g of water. How many grams of NaNO 3(s) are needed to make a saturated solution of 50g of water at 50 C?
- Slide 12
- Practice! Practice: p. 223 # 4-10, p. 226 #1-7, 9, 10 Read: p. 220-226
- Slide 13
- Flame Tests
- Slide 14
- Concentration NOT THE TYPE YOU NEED FOR A TEST
- Slide 15
- Concentration Concentration: quantitative measure of solute in solvent. How much solute is dissolved in solvent. Can be represented by different units, there are different ways of stating concentration. Most commonly used: molar concentration or molarity = _________ = C C =
- Slide 16
- Ex 1: What is the molar concentration of 4.00L solution with 1.54mol NaOH in it?
- Slide 17
- Ex 2: What is the molarity of 0.23mol of sodium sulphate dissolved in 500mL of water?
- Slide 18
- Ex 3: 4.00g of NaOH is dissolved in 250mL of solution. Whats the molarity of NaOH (aq) ?
- Slide 19
- Ex 4: How many mL of 0.400M NaOH solution will contain 1.00g of NaOH?
- Slide 20
- Ex 5: How many moles are in 2.00L of 4.00mol/L solution of NaCl?
- Slide 21
- Ex 6: What is the mass of NaCl in the previous example?
- Slide 22
- Ex 7: Whats the volume when 0.500 moles of NaOH make a 3.00mol/L solution?
- Slide 23
- Ex 8: Calculate the mass of Na2CO3 required to make 3.5L of a 1.2mol/L solution.
- Slide 24
- Ex 9: What volume of 0.500M solution can be made from 12.00g of NaCl?
- Slide 25
- Ex 10: Whats the concentration of a solution with 53.2g of CaCl2 in 5000mL of water?
- Slide 26
- Other Concentration Calculations (% mass, % volume, ppm) Percent by mass: Percent by volume:
- Slide 27
- Ex: Whats the % by mass of NaCl if 9.0g of NaCl is added to 91.0g of water?
- Slide 28
- Ex: Whats the % by volume of ethanol if 15.0mL of ethanol is added to 85.0g of water?
- Slide 29
- Parts per Million (ppm) Parts per million (ppm): same units top and bottom multiplied by a million (10 6 ) Useful for very low concentrations
- Slide 30
- Ex: What is the ppm (m/v) of NaCl if 5.9mg of NaCl is dissolved in 500mL of water?
- Slide 31
- Concentration of Ions in Solution 1. Write a balanced dissociation equation or ionization equation: Ex: Al 2 (SO 4 ) 3(aq) 2. Use the mole ratio and the Factor-Label Method to find the concentration of the ions: Ex: 1.00M Al 2 (SO 4 ) 3(aq). Find [Al 3+ ] and [SO 4 2- ].
- Slide 32
- Slide 33
- Ex: A barium hydroxide solution is 2.00mol/L. Find [Ba 2+ ] and [OH - ].
- Slide 34
- Practice! Practice: p. 316 #1-4, 6, p. 214 #2-12, 15 Read: p. 314-215, p. 203-213
- Slide 35
- Strengths/Weaknesses of Acids/Bases
- Slide 36
- Bronsted-Lowry A/B Ionization/Dissociatio n Equations FILL IN THE HANDOUT AS WE GO
- Slide 37
- How to write equations for ACIDS: General Equation: HA donates H + (proton) to H 2 O (acts as a base):
- Slide 38
- How to write equations for ACIDS: Therefore, a conjugate acid-base pair consists of two substances related to each other by donating/accepting a proton (H+). Ex:
- Slide 39
- How to write equations for ACIDS: The hydronium ion (H 3 O + ) forms from attraction between H + and polar H 2 O. Both H 3 O + and H + are used to measure the strength of an acid (they are used interchangeably).
- Slide 40
- Practice: Identify the conjugate acid- base pairs in the following equations: 1. 2.
- Slide 41
- Practice: Identify the conjugate acid- base pairs in the following equations: 3. 4.
- Slide 42
- Practice: Identify the conjugate acid- base pairs in the following equations: 5. 6.
- Slide 43
- Polyprotic Acids! The last 3 equations are examples of polyprotic acids! Polyprotic acids can lose more than one proton (H + ): Ex: So they can react with H 2 O more than once to produce many H 3 O + ! # times an acid can react = # Hs at the front; each time it reacts, it gets weaker
- Slide 44
- Favouring Stronger Products In all of the above equations, the products are stronger acids and bases than the reactants. Remember: strong acids completely ionize. Weaker acids dont and we can represent this with a forward and reverse arrow. Ex:
- Slide 45
- How to write equations for BASES: 1. If it has an OH - (hydroxide): simply write the dissociation equation General Equation: (these are strong bases!) Ex: NaOH (aq)
- Slide 46
- How to write equations for BASES: 2. If it has no OH- (hydroxide): split the cmpd into its ions and use the anion (-ve one). React the anion with H 2 O to produce OH - Determine the other product (its the anion gaining a H + ). Remember: acids lose H +, bases gain H + General Equation: (these are weak bases!)
- Slide 47
- Ex: Na 2 CO 3
- Slide 48
- Ex: Na 3 PO 4
- Slide 49
- Ex: NH 3
- Slide 50
- Polyprotic Bases Polyprotic bases: can accept more than one proton (H + ) so it can react with H 2 O many times to produce many OH - (hydroxide ions): Ex: # times it can react = # charge
- Slide 51
- Strong vs. Weak Acids/Bases: The stronger the acid, the more H 3 O + it produces, the higher its [H3O+], and the more forward the ionization moves (>99% ionization): General Equation: (There are 7 strong acids and theyre listed on the data sheet)
- Slide 52
- Strong vs. Weak Acids/Bases: The stronger the base, the more OH - it produces, the higher its [OH - ], and the more forward the dissociation moves (>99% dissociation): General Equation: (Strong bases: have OH- and a Group 1 metal/Alkali metal)
- Slide 53
- Strong vs. Weak Acids/Bases: Weak acids and bases only partially ionize and dissociate (