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What is the common ion effect?
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Chem 105 After MT
Chem 105
| Question | Answer |
|---|---|
| What is the common ion effect? | Whenever a weak electrolyte and a strong electrolyte containing a common ion are together in solution, the weak electrolyte ionizes less than if it were alone in solution. |
| Eg of common ion effect? | NaCN/HCN |
| What are buffers? | solutions where pH can stay somewhat constant even if small amounts of strong acid or base are added. They feature common ion effect |
| What makes up a buffer? | weak acid or base and its conjugate ion |
| Is Ch3COOH/CH3COO- a buffer? | yes |
| Is NH4+/NH3 a buffer? | yes |
| Is HCO3-/CO3(2-) a buffer? | yes |
| IS HNO3/NO3- a buffer? | no (HNO3 is a strong acid) |
| What are the two reasons that buffers work? | 1. added H+ is converted to HA by weak base A-. 2. added OH- is converted to water by weak acid HA |
| What is titration? | determining a concencentration by reacting it with a solution of known concentration until an equivalence point is reached. |
| Titration of a weak acid and strong base has a pH of; | above 7 |
| Titration of a strong acid with a weak base has a pH of: | below 7 |
| What does a pH curve look like for a polyprotic acid? | pH jump for each H+ removed |
| Between what type of atoms does a solubility equilibrium exist? | between solid and aqueous solutions |
| What are the units of soluability? | g/L and mol/L |
| What is soluability (S)? | the max amount of solid to dissolve per litre of solution |
| soluability ____ as attractions between solute and solvent _____ | increase, increase |
| as pressure______ Sgas _____ but Ssolid is ______ | increases, increases, unchanged |
| as temperature _____ Sgas ______ but usually Ssolid_____ | increases, decreases, increases |
| generally, you can improve salt soluabilit with | increasing temperature |
| additional soluability rules for Ssalt: | common ion effect of Ssalt. as Ssalt decreases if a common ion is present in solution |
| For salts with basic anions, Ssalt ______ as pH ____ from 7 (gets more_____) | increase, decrease, acidic |
| For salts with acidic cations, Ssalt ____ as pH ___ from 7 (gets more ____) | increase, increases, basic |
| What is electrochemistry? | the study of the relationship between chemical reactions and electrical work (electricity) |
| What is oxidation? | loss of electronsq |
| What is reduction? | gain of electrons |
| What is the oxidation state of an atom? | the charge the atom would have if all its bonds were considered ionic, and have any covalent pairs (of electrons) were deemed to belong to the more electronegative atom, sharing that pair. |
| What are redox reactions? | reactions involving a transfer of electrons from one reactant (one being oxidized) to another reactant (one being reduced) |
| the reductant is being___ | oxidized |
| the oxidant is being _____ | reduced |
| What is a voltaic (galvanic) cell? | devices that use spontaneous redox reactions to do electrical work. ex. wire |
| What is an anode? | electrode where oxidation occurs, losing an e- to the wire. labelled (-) |
| What is an cathode? | electrode where reduction occurs, gaining e- from the wire |
| What is voltage? | the "potential of difference"(emf) of a voltaic cell |
| What are the standard conditions of standard cell potentials | 1 atm for gas, 25*C, 1M |
| What type of properties are voltages? | intensive |
| What is a battery? | one (or more) voltaic cells in series, without the connecting wire |
| What is a lead-acid car battery? | 12V(six 2V stacked cells) |
| What is an alkaline battery? | 1.5 V one cell (primary cell-not rechargeable) |
| What is a lithium ion battery? | 3.7 V secondary cell(rechargeable) |
| What is a hydrogen cell battery? | 1.2 V, fuel continuously flows into cell |
| What is thermodynamics? | the study of transformations of energy. |
| What are the two parts of the universe? | system and surroundings |
| How does a spontaneous process occur? | naturally occurs without work being required |
| What is a reverse process? | idealized process that takes a system from state A to state B via infinitely small changes, that could be reversed |
| What determines the spontaneous direction? | The spontaneous direction is the direction of change that leads to more disorderly dispersal of total energy of the universe. |
| What is Entropy (S)? | the degree of disorder of energy dispersion |
| melting ____ the amount of entropy, freezing is the opposite. | increases |
| What is a microstate? | the state of each molecule in the sample |
| What is the microscopic definition of entropy? | a measure of how many microstates are associated with a particular microstatic state |
| Entropy is positive when moving from | solid to liquid/gas and liquid to gas |
| if S>0 moles of gas is>> | >0 |
| entropy ____ with the dissolving of a salt | increases |
| Because of the 3rd law of thermo, everything has a ___ entropy at temps above absolute zero | positive |
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