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Aqueous chemistry
91392- Demonstrate understanding of equilibrium principles in aqueous systems
| Question | Answer |
|---|---|
| How do you determine whether a substance is a salt or a weak acid/base? | A salt is made up from a positive and a negative ion which is ionically bonded together whereas weak acids and bases are typically covalent compounds. |
| Why are salt solutions great electrical conductors? | This is because salts fully dissociate into their ions, which results in high concentrations of free moving particles in water which are able to carry a charge. |
| What is the PH of a salt solution? | The PH of a salt solution is around 7 meaning that it is neutral |
| Why are weak acids and weak bases poor electrical conductors? | This is because weak bases and weak acids only partially ionize in solution, resulting in a low concentration of ions in solution. |
| List the strong acids: | Hydrochloric acid HCl Sulfuric acid H2SO4 Nitric acid HNO3 Hydrogen Bromide HBr |
| List the strong bases: | sodium hydroxide NaOH Potassium hydroxide KOH Lithium hydroxide LiOH Calcium hydroxide CaOH2 |
| What does Ka mean ? | Acid dissociation constant |
| What does the size of the Ka mean? | The bigger the Ka the stronger the acid (they dissociate more) |
| What is an equilibrium? | A state in a chemical reaction when the rates of the forward and reverse reactions are equal, and the concentrations of reactants and products remain constant. |
| What is le Chateliers principle? | A principle that states that if a system at equilibrium is disturbed by changes in concentration, pressure, or temperature, the system will adjust to counteract those changes and establish a new equilibrium. |
| What is the common ion effect? | When a salt is added to a solution that already contains one of its ions, it decreases the solubility of the salt through the shift in equilibrium. |
| What is a buffer solution? | A solution that resists changes in pH when small amounts of a strong acid or base is added to it. It contains a weak acid and its corresponding conjugate base or a weak base and its corresponding conjugate acid. |
| What is a titration? | A technique used to determine the concentration of an acid or a base by reacting it with a solution of known concentration (titrant) until the reaction is complete, usually indicated by a color change. |
| What does buffer capacity mean? | The ability of a buffer solution to resist changes in pH when an acid or base is added. It depends on the concentrations of the buffer components. |
| What is the Henderson's equation? | An equation used to calculate the pH of a buffer solution. It relates the concentration of the weak acid (HA), the concentration of its conjugate base (A⁻), and the pH of the solution. pH = pKₐ + log([A⁻]/[HA]) |
| Equivalence point | The point in a titration when the moles of the acid and base are equal. It is indicated by a significant change in pH or an observable color change. |
| How do you determine the PH range that a solution will act as a buffer? | It is +-1 from the pKa |
| How does a buffer solution keep the PH relatively consistent? | The added acid or base is neutralized by the weak acid/base to form water and its conjugate and so the Ph of the solution does not significantly change as the H3O+ ions or the OH- ions are removed from the solution. |
| When does PH equal pKa? | At the half equivalence point |
| When will a buffer solution be more effective in neutralizing a strong base? | When the pKa is bigger than the PH which means that the solution is more acidic so will be more effective neutralizing a base. |
| When will the buffer solution be more effective in neutralizing a strong acid? | When the PH is bigger than the pKa which means that the solution is more basic so will be ore effective neutralizing an acid. |
| When is a buffer solution at optimal buffering capacity? | When the pKa is equal to the PH, at this point the concentrations of the weak acid and its conjugate base (or the weak base and its conjugate acid) are approximately equal, which is the ideal condition for the buffer to resist changes in pH effectively. |
| Ks is bigger than Qs, will a precipitate form? | No precipitate forms |
| Qs is bigger than Ks, will a precipitate form? | yes a precipitate forms |
| Ks is equal to Qs, will a precipitate form? | No, a saturated solution forms |
| What is an amphiprotic substance? | A substance which can either donate or accept protons |
| How is Kb related to ka ? | Kb=Kw/Ka |
| Why does the PH of a buffer solution stay the same when water is added? | Because when water is being added it is just diluting the solution and the ratio of acid to base stays the same and so PH stays the same. But the capacity of the buffer decreases |
| How do you calculate [H3O+]? | =Ka x [acid]/[base] |
| What is the Unit for solubility? | molL-1 |
| What are the three OH- related equations not on the formula sheet? | pOH= -log[OH] [OH-]=10-pOH PH + POH = 14 |
| What is the PH range of an indicator? | pKa +-1 |
| What makes buffers more effective ? | When they are concentrated |
Created by:
estherbruce
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