Reactions in Aqueous Solutions

Question 1

Solubility

Answer 1

• Descriptions of Solubility:
  
  • Mass per volume of solvent
  • Molar solubility
  • Solubility Product, Ksp

Question 2

Molality (m)

Answer 2

• One method of describing concentration
• Describes a number of moles of solute being dissolved and what mass of solvent the solute is dissolved in
• Molality (m) = moles of solute/ kilograms of solvent

Question 3

Molarity (M)

Answer 3

• Most common measure of concentration
• Describes how many moles of a solute are dissolved in each litre of the solution

Question 4

Molar Solubility

Answer 4

• We use moles, which means it is the molarity of a solution when it is saturated.
• A solution is saturated when there is as much solute dissolved as can be dissolved in that solution.

Question 5

Solubility Product

Answer 5

• Follows the same rules as any equilibrium constant.
• Ksp = [products] (coefficients becoming exponents)
• Because solids, and pure liquids do not appear in equilibrium constants, the denominator is not there

Question 6

Common Ion Effet

Answer 6

• Says that the presence of an ion in solution will decrease solubility of compounds containing that ion.
• Just another example of Le Chatelier’s Principle.

Question 7

Faraday’s Constant

Answer 7

• F = 96,500 C/mol

Question 8

Salt

Answer 8

• In chemistry a salt is any substance made of anions and cations
  
  • Cations = positively charged; fewer electrons than protons
  • Anions = Negatively charged; greater electrons than protons

Question 9

Ionizations Energy

Answer 9

• The amount of energy needed to remove an electron from an atom
• The term is coined to describe the energy specifically needed to form cation from a neutral atom.
• All atoms hold onto their electrons through the attraction of the positively charged protons in their nucleus.
• Taking an electron away from an atoms means increasing the electron’s potential energy → we are removing it away from the nucleus, to which it is attracted
  
  • This means we are making potential energy less negative, in other words, its actually increasing!
• The idea behind ionization is that we have to transfer enough energy to an outer electron to give it the boost it needs to leave
  
  • The amount of energy required depends on how strongly an atom holds on to its electrons.

Question 10

Ionization energy and Periodic Table

Answer 10

• The atoms on the right side of the table pull more on electrons and atoms on the left side do.

Question 11

Law of conservation of Energy

Answer 11

• Energy can not be created nor destroyed
• When ions form in chemistry, the force that pulls on electrons is usually the attractive force of another atom.
• Sodium loses its valence electron because some other atom pulls it away, stealing that electron. (thats what gets us back to anions)
  
  • If a neutral atom steals an electron, it becomes negative, so it becomes an anion.

Question 12

Electron Affinity

Answer 12

• The energy change that results from adding an electron to an atom.
• It is caused by the same factors involving ionization energy, thus it follows the same general trend.
  
  • Elements further right on the periodic table tend to have higher affinity’s, that is more exothermic, they tend to release more energy
• Example
  
  • The energy cost to steal an electron from sodium is small, while the energy released from the chlorine gains the electron to make it a chlorine anion is large
  • This leads to a much lower energy state, there’s a net release of energy.
  • Lower energy states means a species is less reactive and more stable.

Question 13

Polyatomic IOns

Answer 13

• Groups of atoms covalently bounded together, but the group of atoms as a whole has a charge.
• The vast majority of polyatomic ions involve an oxygen and are negatively charged. Common example are:
  
  • Carbonic acid (H2CO3)
    
    • Forms when carbon dioxide reacts with water
    • If we break it up we have our positive H+ ions and our negative CO3 (must be an anion)
    • Hydrogens can either be positively or negatively charged but they’re only negatively charged when they’re in compounds with metals, because then hydrogen can steal an electron from those metal son the left side of the periodic table
    • Carbonate only has non-meals, so those two hydrogens must be positively charged or cations
    • If they’re cations then the carbonate must cancel their positive charge, so it must be negative and an anion.
      
      • the way to detemrine how negative carbonate is, is to see that we need two positively charged hydrogen atoms attached to out anion in order to create our neutral molecule H2CO3
      • So we need to negative charges to balamce those hydrogen ions out, which can only come from our carbonate anion
      • Since there’s only one carbonate, that one carbonate must have both negative charged.
      • Carbonic acid is a fairly common weak acid