Chapter 4 molarity

1
Chapter 4
Aqueous solutions
Types of reactions

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Parts of Solutions
 Solution- homogeneous mixture.
 Solute- what gets dissolved.
 Solvent- what does the dissolving.
 Soluble- Can be dissolved.
 Miscible- liquids dissolve in each other.

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Aqueous solutions
 Dissolved in water.
 Water is a good solvent
because the molecules are
polar.
 The oxygen atoms have a
partial negative charge.
 The hydrogen atoms have a
partial positive charge.
 The angle is 105ºC.

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Hydration
 The process of breaking the ions of
salts apart.
 Ions have charges and attract the
opposite charges on the water
molecules.

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Solubility
 How much of a substance will dissolve
in a given amount of water.
 Usually g/100 mL
 Varies greatly, but if they do dissolve
the ions are separated,
 and they can move around.
 Water can also dissolve non-ionic
compounds if they have polar bonds.

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Electrolytes
 Electricity is moving charges.
 The ions that are dissolved can move.
 Solutions of ionic compounds can
conduct electricity.
 Electrolytes.
 Solutions are classified three ways.

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Types of solutions
 Strong electrolytes- completely
dissociate (fall apart into ions).
 Many ions- Conduct well.
 Weak electrolytes- Partially fall apart
into ions.
 Few ions -Conduct electricity slightly.
 Non-electrolytes- Don’t fall apart.
 No ions- Don’t conduct.

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Types of solutions
 Acids- form H+ ions when dissolved.
 Strong acids fall apart completely.
 many ions
 H2SO4 HNO3 HCl HBr HI HClO4
 Weak acids- don’ dissociate completely.
 Bases - form OH- ions when dissolved.
 Strong bases- many ions.
 KOH NaOH

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Measuring Solutions
 Concentration- how much is dissolved.
 Molarity = Moles of solute
Liters of solution
 abbreviated M
 1 M = 1 mol solute / 1 liter solution
 Calculate the molarity of a solution with
34.6 g of NaCl dissolved in 125 mL of
solution.

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Molarity
 How many grams of HCl would be
required to make 50.0 mL of a 2.7 M
solution?
 What would the concentration be if you
used 27g of CaCl2 to make 500. mL of
solution?
 What is the concentration of each ion?

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Molarity
 Calculate the concentration of a solution
made by dissolving 45.6 g of Fe2(SO4)3
to 475 mL.
 What is the concentration of each ion?

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Making solutions
 Describe how to make 100.0 mL of a
1.0 M K2Cr2O4 solution.
 Describe how to make 250. mL of an
2.0 M copper (II) sulfate dihydrate
solution.

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Dilution
 Adding more solvent to a known solution.
 The moles of solute stay the same.
 moles = M x L
 M1 V1 = M2 V2
 moles = moles
 Stock solution is a solution of known
concentration used to make more dilute
solutions

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Dilution
 What volume of a 1.7 M solutions is
needed to make 250 mL of a 0.50 M
solution?
 18.5 mL of 2.3 M HCl is added to 250 mL
of water. What is the concentration of the
solution?
 18.5 mL of 2.3 M HCl is diluted to 250 mL
with water. What is the concentration of
the solution?

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Dilution
 You have a 4.0 M stock solution.
Describe how to make 1.0L of a .75 M
solution.
 25 mL 0.67 M of H2SO4 is added to 35
mL of 0.40 M CaCl2 . What mass
CaSO4 Is formed?

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Types of Reactions
 Precipitation reactions
 When aqueous solutions of ionic
compounds are poured together a solid
forms.
 A solid that forms from mixed solutions
is a precipitate
 If you’re not a part of the solution, your
part of the precipitate

Chapter 4 molarity

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Chapter 4 molarity