Download - Ch 15/16 Water and its Properties
Ch 15/16 Water and its Properties
1mL = 0.001L
• Vocabulary (tested-star these terms)• • solute, solvent, pressure
• temperature, agitation, concentration• saturated, unsaturated, % composition– *** Molarity ***
Surface tension – hydrogen bonds create an inward pull that minimizes surface area. Mr. B:: Creates a solid shell on top of water that can support light weight items (small bugs, pepper flakes). Createsraindrops.
Hydrogen bonds between water molecules.
All atoms like to have 8 electrons in valance shell (2 s and 6 p’s.) They are in 4 pairs of two. 2 pairs grab H. 2 pairs grab other H20 molecules. Discuss Ice in rivers and circle of life.Show water / oil bottles with 2 dyes
Aqueous solution – water w/ dissolved particles (aq)
Solvent – water (dissolver)
Solute – salt (dissolvee)(NEW WORD?)
Surfactants • Stop or break down the hydrogen bonding
• Teacher Notes and You tube Video link:
• http://www.youtube.com/watch?v=hKoB0MHVBvM
• When you pair carbonated soda and Mentos candies, you can create an overflow of fun. Perform your experiments outside, in an open area, and use protective eye gear. The nature of the reaction between the soda and candy is a matter of debate among scientists. The effect may be due to a physical or chemical cause. Most believe that ingredients in the candies cause a break in surface tension in the liquid, allowing new bubbles to more easily form, while carbon dioxide bubbles form well on the pitted surface of the candies
Read more: Mentos and Soda Experiments | eHow.com http://www.ehow.com/list_7487590_mentos-soda-experiments.html#ixzz2Ow8u7tmr
Solvation: a solute dissolves or dissociates into ions(happens with most soluble ionic compounds and acids)Electrolyte: will conduct electricity when dissolved in a liquid.
3 ways to speed up solvation HeatingStirringIncreasing surface area of the solute (powder)
A solution does not have to contain a liquid
Air is a solution 78% nitrogen
14karat gold is a solution58% gold 42% Copper
Solid Hydrate:A crystal with big spaces that water can easily move into.
Demo: Na2SO4•10H2O(s) Show crystal model of
Na2SO4
Add some H2O models to it.
Solid Hydrate
HydratesCuSO4•5H2O(s)
1 (CuSO4) to 5 ( H2O) ratioIn this solid compound there are 5 water molecules for every one CuSO4.
What is the molar mass of the hydrate?Add the molar mass of CuSO4 and 5 water molecules.
Cu S O4• 5H2O(s)
CuSO4•5H2O(s)
CuSO4•5H2O(s)
What is percent H2O?
Percent H2O Hydrate:
CuSO4•5H2O(s)
What is percent H2O?
What is the molar mass of Na2SO4•10H2O(s)
What is the molar mass of Na2SO4•10H2O(s)
What is the percent water in this hydrate? Na2SO4•10H2O(s)
What is the percent water in this hydrate? Na2SO4•10H2O(s)
What is the percent water in this hydrate? Na2SO4•10H2O(s)
What is the percent water in this hydrate? Na2SO4•10H2O(s)
What is the correct sig fig in the answer: 56%
What is the percent sodium in this hydrate? Na2SO4•10H2O(s)
WOD:
% Chem = Mass Chem x 100% Total Mass
What is the percent sodium in this hydrate? Na2SO4•10H2O(s)
What is the correct sig fig in the answer: 14%
How many grams of water are in a 34g sample of Na2SO4•10H2O(s)?
How many grams of water are in a 34g sample of Na2SO4•10H2O(s)?
56% x 34g = 19g H20
Solubility – g of solute per 100g of solvent at a certain temperature
Below: 2 different liquids, same amount of solute (dye). Note black bars.
Does solubility change with temperature?
Does solubility change with temperature?
saturated solution - will dissolve no more solute (at that temperature). Excess
usually makes a pile of crystals on the bottom.
unsaturated solution – will dissolve more solute (at that temperature)
(left 3 beakers on next slide)
As you add more solute, from left to right Dilute More Concentrated Saturated Saturated
Since 3 on right are saturated, keep adding solute, but they don’t get darker. No more dissolves into them.
Dilute vs concentrated
Supersaturated solution – contains more solute then should be dissolved at a
temperatureex…heating then cooling a
solution
Supersatured videoshttp://www.youtube.com/watch?v=XSGvy2FPfCw
http://www.youtube.com/watch?v=HnSg2cl09PI
3 min Long one if you have extra time: http://www.youtube.com/watch?v=1y3bKIOkcmk
New Subject: Gas Solubility: S1 = S2
P1 P2Called Henry’s Law.
Amount of gas dissolved in a liquid.
Solubility of a gas in a liquid is directly related to pressure.
Miscible – liquids dissolve in each other. (liquids that can mix
together)Immiscible – Guess?
Is this lava lamp miscible or immiscible?
16.2 Molarity Pg 526Molarity tells us the number of
moles of solute in exactly 1 liter of a solution.
M = mol ÷ L (of solution)
Do not confuse lower case m (Molality) and Capitol M (Molarity)
Molality: m = moles of Solute Pg 538 kg of solvent
Concentrations(Notice Case of M or m)M = Molarity = Volume basedm = Molality = Mass based
Molarity: M = mol ÷ L (of solution)
molality: m = moles of Solute Pg 538 kg of solvent
Concentrations (Note case of M / m) Molarity: M = Volume based of SOLUTION! (after mix) molality: m = Mass based of SOLVENT! (before mix) Solute + Solvent = Solution
We need two pieces of information to calculate the molarity of a solute
in a solution: The moles of solute present in the
solution. The volume of (final) solution (in
liters) containing the solute.
What is the molarity of a 125mL solution with 12.5g of NaCl
dissolved in it?
What is the molarity of a 125mL solution with 12.5g of NaCl dissolved in it?
Do we have moles and liters?
What is the molarity of a 125mL solution with 12.5g of NaCl dissolved in it?
What is the molarity of a 125mL solution with 12.5g of NaCl dissolved in it?
What is the molarity of a 125mL solution with 12.5g of NaCl dissolved in it?
What is the molarity of a 125mL solution with 12.5g of NaCl dissolved in it?
How many liters of 18.1M HCl are needed to obtain 2.55 mol?
How many liters of 18.1M HCl are needed to obtain 2.55 mol?
Quiz 16.2A 137g sample of BaCl2.5H2O is dried in an oven.
1a) How many grams of water will be driven off?
1b) How many grams of BaCl2 will remain?
2. What would the molarity of a solution be if the above 137g sample of BaCl2.5H2O was instead
dissolved to make a 0.75L solution?
Answers Quiz 16.2A 137g sample of BaCl2.5H2O is dried in an oven. 1a) How many grams of water will be driven off?
1b) How many grams of BaCl2 will remain?
Quiz 16.2A 137g sample of BaCl2.5H2O is dried in an oven. 2. What would the molarity of a solution be if the above 137g sample of BaCl2.5H2O was instead
dissolved to make a 0.75L solution?
Quiz 16.2A 137g sample of BaCl2.5H2O is dried in an oven. 2. What would the molarity of a solution be if the above 137g sample of BaCl2.5H2O was instead
dissolved to make a 0.75L solution?
• 90/297(100%)=30.3% water• 0.303 (137)= 41.5g water• 137-41.5 or (207/297x137) = 95.5g BaCl2
By adding water you can dilute the molarity
M1V1=M2V2
By adding water you can dilute the molarityM1V1=M2V2
When you ADD WATER, moles of solute stays the same.
A 0.500L bottle of vinegar is 0.88 molar. Water is added until the
Molarity is 0.22. What is the new volume?
A 0.500L bottle of vinegar is 0.88 molar. Water is added until the
Molarity is 0.22. What is the new volume?
A 0.500L bottle of vinegar is 0.88 molar. Water is added until the
Molarity is 0.22. What is the new volume?
A 0.500L bottle of vinegar is 0.88 molar. Water is added until the
Molarity is 0.22. What is the new volume?
A stock solution of 18.1M HCl is available in the store room. How
much stock solution should be obtained to create 2.5L of 0.52M
solution?
A stock solution of 18.1M HCl is available in the store room. How much
stock solution should be obtained to create 2.5L of 0.52M solution?
18.1M (X) = (0.52M) 2.5LX = 0.072L
75.5mL of 1.85M CaCl2 is added to 22.4mL of 3.67M AgNO3
(assume 97.9mL is the final volume and AgCl(s)).
What is the molarity of Ca(NO3)2(aq)?
75.5mL of 1.85M CaCl2 is added to 22.4mL of 3.67M AgNO3
(assume 97.9mL final and AgCl(s)). What is the molarity of Ca(NO3)2?
75.5mL of 1.85M CaCl2 is added to 22.4mL of 3.67M AgNO3
(assume 97.9mL final and AgCl(s)). What is the molarity of Ca(NO3)2?
75.5mL of 1.85M CaCl2 is added to 22.4mL of 3.67M AgNO3
(assume 97.9mL final and AgCl(s)). What is the molarity of Ca(NO3)2?
75.5mL of 1.85M CaCl2 is added to 22.4mL of 3.67M AgNO3
(assume 97.9mL final and AgCl(s)). What is the molarity of Ca(NO3)2?
75.5mL of 1.85M CaCl2 is added to 22.4mL of 3.67M AgNO3
(assume 97.9mL final and AgCl(s)). What is the molarity of Ca(NO3)2?
A change in a property of a solvent that depends on the concentration of
dissolved solute(s) particles is called a colligative property.
Colligative properties are vapor pressure lowering, boiling point elevation, freezing point lowering
Number of solute particles in a solution determines colligative
properties.
A Comparison of Some of the Properties of Pure Water and an Aqueous NaCl Solution
property pure water NaCl solution
vapor pressure 23.8 torr 23.1 torr
boiling point 100.0oC 100.8oC
freezing point 0.0oC -3.0oC
Why do you add salt to water when cooking pasta?
When a solute is added to a solvent, the vapor pressure of the solvent (above the resulting solution) is less than the vapor
pressure above the pure solvent. The boiling point of a solution, then, will be greater than the boiling point of the pure solvent because
the solution (which has a lower vapor pressure) will need to be heated to a higher temperature in order for the vapor pressure to become equal to the external pressure
(i.e., the boiling point).
Calculate the percent composition and the molarity of the solution.
20g of NaCl is added to 100mL of water. The volume of this solution
is 114mL.
(remember 1.00mL=1.00g for pure water)
Calculate the percent composition and the molarity of the solution.
20g of NaCl is added to 100mL of water. The volume of this solution is 114mL.
(remember 1.00mL=1.00g for pure water)
The mass of the solute in the solution.
The mass of the solution.
Start Bell work 4 here:. Dilution and Stoich problems
Dilution and Stoichiometric ProblemsBW Day 4, Problem 6
What is the M of a 250ml , 12M HCl solution that is diluted to
4.5L.Clue: M1V1 = M2V2
Subscript 1 and 2 refer to the same solution at 2 different
times.
Dilution and Stoichiometric ProblemsBW Day 4, Problem 8
What is the Molarity of the final solution when 66.6mL of 12.57M HCl is added
to 257 mL of 2.77M Clue. M = n/L
Find n = n1 + n2 n1 = moles of 66.6mL 12.57M HCL
n2 = moles of 257mL 2.77M HCLVolume = V1 + V2 (in Liters)
M = n = n1 + n2 V V1 + V2
m = Molality = moles of Solute Pg 526 kg of solvent
Concentrations(Notice Case of M or m)M = Molarity = Volume basedm = Molality = Mass based
Kb is for boiling. Kf is for freezing.ΔT = K x m
Molarity: M = mol ÷ L (of solution)
molality: m = moles of Solute Pg 538 kg of solvent
Concentrations (Note case of M / m) Molarity: M = Volume based of SOLUTION! (after mix) molality: m = Mass based of SOLVENT! (before mix) Solute + Solvent = Solution
WATER ONLY
Remember mass WATER ONLY
1 mL = 1g = .001 kg
1000 mL = 1000g = 1kg
These conversion are for WATER ONLY