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53 Cards in this Set
- Front
- Back
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Rate of reaction |
Change of concentration of a substance per unit of time. |
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How can you measure rate from a concentration time graph? |
Draw a tangent and calculate the gradient at that specific point. |
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Initial rate of reaction |
Change in concentration of a reactant per unit of time when t=0 |
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How can the reaction rate of an acid Base reaction be monitored? |
Measuring pH with a pH meter or titration |
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How can the reaction rate of a gas producing reaction be monitored? |
Measuring change in volume, pressure or loss in mass of reactants. |
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How can the reaction rate of a reaction which has visual changes be monitored? |
Formation of a precipitate or a colour change. |
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What is the overall order of a reaction? |
The sum of individual orders |
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K |
Rate constant |
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Half life |
Time taken for the cencentration of a reactant to reduce by half |
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What happens to half life's in zero, first and second order reactions? |
Zero- decreases with time First- remains constant Second -increases with time |
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How do you work out initial rate from a clock reaction? |
Initial rate is proportional to 1/time |
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As K increases, that rate of reaction... |
Increases |
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As temperature increases, k... |
Increases. Usually it doubles every 10 degrees. |
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What is the rate determining step? |
The slowest step in a multi step reaction mechanism. |
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What is an intermediate? |
A species formed in one step of a multi step reaction that is used up in another step so is not part of the overall reaction. |
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Kc |
Equilibrium constant Equilibrium constant |
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Homogeneous equilibria |
All species have the same physical state |
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Heterogeneous equilibria |
Species have a mixture of physical states |
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If Kc is larger than 1 |
The reaction favours products and the equilibrium lies to the right. |
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If Kc is smaller than 1 |
The reaction favours reactants and the equilibrium lies to the left. |
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When the reaction is endothermic, delta H is possotove, as temperature increases... |
Kc increases |
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When the reaction is exothermic, delta H is negative, as temperature increases... |
Kc decreases |
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As temperature increases, the equilibrium shifts in... |
The endothermic direction |
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As temperature decreases the equilibrium shifts in the... |
Exothermic direction |
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If the concentration of the reactants is increased, the equilibrium shifts... |
Towards the products |
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If presures is increased equilibrium shifts... |
Towards the side with fewer gaseous molecules |
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What is a dibasic acid? |
An acid which can react twice releasing two protons. The second reaction is usually reversable. |
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What is an acid Base pair? |
A pair of two species that transform into each other by gain or loss of a proton |
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What is pH? |
-log [H+(aq)] |
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If the pH value is very large, the H+ value will be... |
Very small |
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Name 6 strong acids |
HCl HNO3 H2SO4 HBr HI HClO4 |
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What is a strong acid? |
An acid that completely disociates in water |
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What is the acid dissociation constant? Ka |
Ka = [H+][A-]÷[HA] |
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How can you calculate H+ of a strong acid? |
[H+]=[HA] |
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How can you calculate [H+] of a weak acid? |
[H+]=[A-] |
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The ionic product of water, Kw |
[H+][OH-] = 1x10^-14 |
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Three most common strong bases |
NaOH KOH Ca (OH)2 |
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What temperature must a strong alkali be to determine it's pH? |
25 degrees |
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What is a buffer solution? |
A mixture that minamises pH changes on addition of small amounts of acid or Base |
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When adding acid to a buffer solution which way does the equilibrium shift? |
Left |
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When adding alkali to a buffer solution which way does equilibrium shift? |
Right |
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What equation can be used to work out the pH of buffer solutions? |
[H+]=Ka × [HA] ÷ [A-] |
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What is the pH range blood plasma needs to be between? |
7.35-7.45 |
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Which weak acid forms an important buffer in blood? |
H2CO3 Carbonic acid |
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How is carbonic acid (H2CO3) removed from the blood? |
It is converted to aqueous CO2 by enzymes. The lungs then convert it to gas and exhale it. |
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Equivalence point |
The point in a titration at which the volume of one solution has reacted exactly with the volume of the second solution |
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Describe the rise in a titration curve |
A slight rise in pH A sharp rise in pH A slight rise in pH |
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What does it mean when an indicator has reached its end point? |
The point in a titration where there are equal concentrations of the weak acid and conjugate Base forms of the indicator. The colour is usually a mix of the two |
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Standard enthalpy change of neutalisation |
The neutralisation of and aqueous acid by and aqueous Base to form one mole of H20 under standard conditions |
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Why does a weak acid have a less exothermic enthalpy change than a strong acid? |
Because the acid must first fully dissociate so it can be naturalised which requires energy because bonds are broken. |
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Why do you get the same enthalpy change for the naturalisation of strong acids? |
Because they dissociate fully the only reaction taking place is H+ + OH- goes to H20 which is the same for every reaction |
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Dynamic equilibrium |
The equilibrium that exists in a closed system when the rate of forward reaction is equal to the rate of the reverse reaction |
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When conc. In a buffer solution are equal |
[Ph]=[kpa] |
