PPQ P1 Flashcards
(28 cards)
2018 P1
Platinum acts as a heterogenous catalyst in the reaction between ammonia and oxygen. It provides an alternative route with a lower Ea. Describe the stages of this alternative route
- reactants adsorbed onto platinum surface
- bonds breaking/weakening
- desorption of product
2018 P1
Explain how the salt bridge provides an electrical connection between the 2 solutions
allows ions to move
2018 P1
State why the left hand electrode does not have an electrode potential of +0.34V
concentration of solution isn’t 1.0 mol dm^-3
2018 P1
Why might the EMF of the cell decrease to 0V
the concentration of Cu 2+ ions in the 2 solutions becomes equal
2019 P1
Describe the process of electrospray ionisation
- sample is dissolved in a volatile solvent
- sample is injected through a hypodermic needle at a high voltage, producing a fine mist
- sample is ionised by gaining a proton
2019 P1
State the meaning of the term periodicity
repeating pattern across a period
2019 P1
Explain why Copper (I) Iodide is a white solid
- 3d subshell is full
- can’t excite e- from a lower energy d subshell to a higher energy d subshell
- can’t absorb white light
2020 P1
Explain why the enthalpy of hydration becomes less exothermic from Li+ to K+ (down group 1)
- charge remain same
- size increases
- weaker attraction between the delta negative O of water and positive metal ion
2021 P1
State the meaning of the term enthalpy change
change in heat energy at a constant pressure
2021 P1
State why the enthalpy of hydration of Ca2+ is less exothermic than that of the enthalpy of hydration of Mg2+
- Ca2+ is bigger than Mg2+
- weaker attraction to delta negative O in water
2021 P1
Fe2+ ions catalyse the reaction between peroxodisulfate(VI) ions and iodide ions in
aqueous solution.
S2O8 2–(aq) + 2 I– (aq) →
2SO4 2– (aq) + I2 (aq)
1) Explain why this reaction is slow before the catalyst is added.
2) Give two equations to show how Fe2+ ions catalyse this reaction.
3) Explain why Zn2+ ions don’t catalyse the reaction
1) Two negative ions repel so activation energy is high
2) i) 2 Fe2+ + S2O8 2– → 2 SO4 2– + 2 Fe3+
ii) 2 Fe3+ + 2 I– → 2 Fe2+ + I2
3) doesn’t have a variable oxidation state
2021 P1
Explains why an aqueous solution containing [Fe(H2O)6]3+ ions has a lower pH than an aqueous solution containing [Fe(H2O)6]2+ ions
- Fe3+ ions are smaller and have a greater charge than Fe2+
- Fe3+ ions are more polarising
- weakens the O-H bonds in water ligands
2021 P1
Explain why the value of Kw increases as the temperature increases
- equilibrium is endothermic in forwards direction
- equilibrium shifts to right to oppose increase in temp
2021 P1
Suggest why the pH probe is washed with distilled water between each of the calibration measurements
so different solutions don’t contaminate each other
2021 P1
Explain why the volume of NaOH solution added between each pH measurement is smaller as the endpoint of the titration is approached
large change in pH near end point
2021 P1
State the meaning of the term electrochemical series
list of electrode potentials in correct order
2021 P1
i) Equation for reaction that occurs at the +ve lithium cobalt oxide electrode
ii) Equation for the reaction that occurs at the -ve lithium electrode
i) Li+ + CoO2 + e- → LiCoO2
ii) Li → Li+ + e-
2022 P1
Give 2 features of a reaction in dynamic equilibrium
1 = forwards and backwards reactions occur at equal rates
2 = concentration of reactants and products remain constant
2022 P1
i) State how a buffer solution can be made from solutions of KOH and CH3COOH
ii) Give an equation for the reaction between KOH and CH3COOH
iii) State how this buffer solution resists changes in pH when a small amount of acid is added
i) add excess CH3COOH to KOH
ii) KOH + CH3COOH → CH3COOK + H2O
iii) added acid reacts with CHCOO-
2022 P1
Give an equation for the reaction between aluminium oxide with sulfuric acid
Al2O3 + 3 H2SO4 → Al2(SO4)3 + 3H2O
2022 P1
Identify a reagent or test that could be used to distinguish between aqueous solutions of sulfur dioxide and sulfur trioxide with the same concentrations.
State the observation in each case.
Reagent/Test: pH meter
Observation with Sulfur Dioxide Solution = pH 2-3
Observation with Sulfur Trioxide Solution = pH 0-1
2022 P1
i) Explain why aqueous solutions containing [CuCl4]2- ions are yellow
ii) By reference to aqueous copper(II) ions, state the meaning of each of the 3 terms in the equation ΔE = hv
iii) state 3 ways in which a transition metal complex can be changed to alter its colour
i)
- absorbs certain frequencies of white light
- electrons in lower energy d subshell excited to a higher energy d subshell
- colour absorbed is the light reflected
ii) ΔE is the energy gained by the (excited) electrons. h is (Planck’s) constant. v is frequency of light
iii) 1 = change in ligand
2 = change in coordination number
3 = change in oxidation state
2022 P1
i) suggest why it’s important that the colorimeter for each sample has the same dimensions
ii) suggest why the coloured filter is used
iii) suggest one reason why a colorimetric method might be chosen in preference to titration
i) absorpion depends on distance travelled through solution
ii) to select the colour/frequency that’s (most strongly) absorbed
iii) quicker to analyse extracted samples
2022 P1
Suggest the function of the porous separator in diagram
allows ions to move
