F325 Flashcards
What is a conjugate acid?
A species formed when a proton is added to a base.
What is the colour change for Cu2+ and OH-?
Blue solution to pale blue precipitate.
What is the colour change for Fe2+ and OH-?
Green solution to dark green precipitate. Turns rust coloured in air.
What is the colour change for Fe3+ and OH-?
Yellow solution to rust coloured precipitate.
What is the colour change for Co2+ and OH-?
Pink solution to blue precipitate.
What is the colour change for Mn2+ and OH-?
Pink solution to creme precipitate.
What is the colour change for Cu2+ and excess NH3?
Blue solution to pale blue precipitate, followed by dark blue solution (if ammonia is in excess).
H2O + NH3 NH4+ + OH-
The precipitate is caused by OH- ions.
What is the colour change for Cu2+ and concentrated HCl?
Blue solution to yellow solution (which looks green due to the equilibrium).
What is the colour change for Co2+ and concentrated HCl?
Pink solution to blue solution.
What is a buffer solution and how is it formed?
A system that minimises the change in pH when small amounts of acid or base are added.
It is formed from a weak acid and a salt of the weak acid.
What is the enthalpy change of neutralisation?
The enthalpy change when aqueous acid and base react to form one mole of water.
What are two advantages of FCVs over internal combustion powered vehicles?
There are less/no CO2 emissions.
Fuel cells are more efficient than internal combustion engines (heat engines).
Name three ways that hydrogen could be stored.
- As a liquid under pressure.
- Adsorbed to a surface of a solid material.
- Absorbed with in a solid material.
What are limitations of hydrogen fuel cell technology?
Storing and transporting hydrogen is difficult. It could be unsafe, it is expensive to develop liquid storage solutions and ad/absorbing solids have limited life cycles.
The fuel cells themselves have a limited lifetime.
Toxic chemical are used in the production of fuel cells.
What are limitations of a future hydrogen economy?
Public and political acceptance of hydrogen as a fuel.
Initial manufacture of hydrogen requires energy which may have come from fossil fuels.
A lot of new infrastructure would have to be built.
How does ligand substitution apply to oxygen transport in the blood.
O2 donates an electron pair and forms a coordinate bond with Fe2+.
When required the O2 is substituted for anther ligand, usually CO2.
Why is CO toxic?
The complex with Fe2+ and CO has a very high stability constant. This makes the CO coordinate bond very strong and less likely to break.
Describe the bonding in platin. How does platin treat cancer?
The ligands donate an electron pair and form a coordinate bond. Platin binds to DNA of cancer cells and stops the from duplicating themselves.
Describe how a buffer solution is formed.
Excess weak acid reacted with a metal to form a salt of the week acid.
Explain how buffer solutions work.
Add small amounts of acid: equilibrium shifts to the left.
Add small amounts of alkali: equilibrium shifts to the right.
Describe an experiment to measure enthalpy change of neutralisation.
- React acid and alkali together. 1 molar HCl and NaOH.
- Record the temperature change of the solution.
- Q = mc/\T, where m is the mass of reactants.
- Energy / moles of water that would be formed.
- Enthalpy of neutralisation = -Q/mol (exothermic).
What should be mentioned when comparing enthalpy of solution changes?
- Ionic radius.
- Which has the most exothermic lattice enthalpy.
- Which has the more exothermic hydration enthalpy (the one that has a stronger attraction with water).
- Enthalpy change of solution is more affected by lattice enthalpy than by hydration enthalpy.
In a worded Kc question equilibrium question…
The change in conditions will cause the concentration of one to change more than the other.
Concentrations will increase/decrease until Kc is restored.
Define the term order.
The power to which the concentration of a reactant is raised in the rate equation.
What is the rate constant?
A constant that links the rate of reaction with the concentration of reactants raised to their order.
What is the half-life of a reaction?
The time taken for the concentration of a reactant to reduce by half. It is independent of concentration.
Define the R.D.S.
The slowest step in the mechanism of a multistage reaction.
List what the gradient for conc-time graphs represent.
- Negative linear - zero order.
- Curve, constant half life - first order.
- Curve, stepper and non constant half life - second order.
Describe the initial rates method for finding the order.
- Perform a series of experiments at the same temperature, changing the concentration of one reactant each time.
- Gradient at t = 0 of a conc-time graph shows the initial rate.
- Plot initial rate against conc to find the order:
Gradient = 0 - zero order.
Positive linear - first order.
Curve - second order (or higher).
Other than the initial rates method, how can the order be found?
Measure the concentration of a reactant continuously as the reaction goes on and plot a conc-time graph to find the order.
The order of a reactant can ONLY be found by experiment. What is the overall order of a reaction?
Overall order is the sum of individual orders.
What is the relationship between the rate constant and temperature?
The rate constant increases with temperature. The relationship is NOT linear, but is a curve of increasing gradient.
What does the acid dissociation constant show?
The extent of dissociation. The percentage of dissociation = 100 X [H+]/[A-].
For a diprotic acid or dibasic base, how do you find pH?
-log10(2[H+]).
10^-pH = 2[H+]
Why is water left out of equilibrium expressions?
The concentration of water is much greater than the concentration of ions and is considered constant.
How do you calculate the pH of a diluted solution?
[H+]’ = [H+] x og volume / new volume.
The dissociation of water is an…
…endothermic process because bonds are broken.
H2O H+ + OH- shifts to the right when temperature is increased.
Explain how buffer solutions are applied to blood pH control.
H2CO3 H+ + HCO3-
Carbonic acid and hydrogen carbonate are used to control blood pH.
What is the difference between a fuel cell and an electrochemical cell?
A fuel cell converts energy from the reaction of a fuel with oxygen into electrical energy.
An electrochemical cell can be made up of any two half cells.
What is the reaction in an hydrogen fuel cell?
2H2 + O2 —-> 2H2O
Define enthalpy change of hydration.
The enthalpy change when one mole of gaseous ions form one mole of aqueous ions.
Define standard electrode potential.
The emf of a half cell compared with a standard hydrogen electrode in standard conditions.
What are assumptions of the ka expression?
[H+] = [A-]
Some water has dissociated, but it is such a small amount that it won’t affect the pH to 2 dp.
Concentration of acid = [HA]
Since it is a weak acid, a very small percentage of the acid has dissociated.
How is enthalpy if neutralisation calculated?
React equal volumes of one mol/dm3 HCl and NaOH. Record the initial temperature and the final temperature of the reaction.
Q = mc/\T where m is the mass of reactants.
/\H = Q/moles of water formed.
