aqueous reactions + stoichiometry

electrolytes

compounds that dissolve in water to produce a solution that conducts electricity

strong electrolytes ____ become ions when dissolved in water

completely

example of strong electrolytes

• ionic compounds

• strong acids

weak electrolytes ____ become ions when dissolved in water

only partially (a very small amt)

examples of weak electrolytes

weak acids (anything with H- that’s not a strong acid)

strong acids

HCl, HNO3, H2SO4, HBr, HI, HClO3, HClO4

non-electrolytes

most covalent compounds dissolve but don’t produce ions

diatomic elements

H, O, Cl, Br, I, F, N

gas-forming reactions

1) acid + carbonate compounds

HC₂H₃O_{2 (aq)} + NaHCO_{3 (aq)} → H₂O _(l) + CO_{2 (g)} + NaC₂H₃O_{2 (aq)}

2) acid + sulfite compounds

H___ + ____SO₃ → H₂O _(l) + SO_{2 (g)} + ____

monoprotic

acid that can donate 1 H⁺ that reacts with NaOH in a 1:1 molar ratio

oxidation

loss of electrons (charge INCREASES)

reduction

gain of electrons (charge decreases

displacement reactions are always/sometimes/never redox

never

single displacement reactions are always/sometimes/never redox

always

oxidation numbers/states

we assign “charges'“ to atoms in a covalent compound to help us determine whether a particular element is being oxidized or reduced

• assign electrons in a bond to the atom with the higher En

rules for assigning oxidation numbers

1. sum of ox. # in all atoms must be equal to net charge of substance. if substance contains polyatomic ion, all ox. # in polyatomic ion add to charge of ion

2. in compounds, alkali metals are +1. alkaline earth metals are +2

3. in compounds, fluorine is -1 (highest En)

4. in compounds, hydrogen is +1 (NM with lowest En)

5. in compounds, oxygen is -2 (2nd highest En)

bridge method

1. assign oxidation numbers

2. identify which atoms are oxidized and which are reduced

3. draw a line (bridge) connecting reduced element to same element in products. do the same for oxidized element

4. figure out how many atoms of each element you would need so that the number of electrons lost = number of electrons gained. add coefficients to equation

5. balance any remaining elements by inspection (if reaction is in skeletal or net ionic form, do not balance H and O yet)

6. if its net ionic or skeletal form, add H+ or OH- to the side (depending on if it was acidic or basic) in order to balance the charge. then add H2O to one side to balance H or O atoms

half-reaction method

1. divide rxn into half reactions, one showing oxidation and the other showing reduction

2. Balance each half-reaction separately

   1. balance elements other than H or O

   2. balance O by adding H2O to other side

   3. balance H by adding H+ to one side

   4. balance charge by adding electrons

3. scale up coeffs in each reaction so electrons lost = electrons gained

4. recombine half reactions and reduce (cross out electrons, reduce H2O and H+ if necessary)

5. if reaction is basic, identify number of H+ in your answer so far, and add that same number of OH- to each side (bc its already balanced). Combine H+ and OH- that are the same side of the arrow to form H2O. Simplify if necessary.