AS/A2 mixed questions Flashcards
Which bonds or interactions are responsible for the higher boiling point of hydrogen iodide
Induced dipole dipole interactions
Describe a method to obtain a pure dry sample of alkene from alcohol
Use separating funnel , separate organic and aqueous layer
dry with anhydrous salt e.g. MgSO4
Redistill
What are bond angles for
C-H
O-H
COOH
C-H = 109.5
O-H = 104.5
COOH = 120
How could the student measure the pH continuously as the NaOh is added
Use a pH meter
Suggest why I2 is not very soluble in water
I2 is non polar
it does not form H bonds with water
What type of reaction has the greatest atom economy
Addition
Explain why the boiling point of PH3 is lower than the boiling point of NH3
NH3 has hydrogen bonding and PH3 does not have hydrogen bonding
Hydrogen bonding is stronger and requires more energy to overcome the bond
Explain why the boiling point of PH3 is lower than the boiling point of AsH3
AsH3 has more electrons than PH3
Therefore has stronger London Forces and more energy is required to overcome the bond
Explain why a CF4 molecule has polar bonds but does not have an overall dipole
It has polar bonds because F is more electronegative than C atom
It has no overall dipole as the dipoles cancel and is a symmetrical shape
what is bond angle for COOH
120 - TRIGONAL planar
what give the numerical value of the Avogadro constant
The number of electrons lost by 20.05g of calcium when it reacts with oxygen
Explain what is meant by the term weighted mean mass
The mean mass taking into account the relative abundancies of the
isotopes
A closed system is required for dynamic equilibrium to be established.
State one other feature of this dynamic equilibrium.
The rate of the forward reaction equals rate of the backward reaction
What conditions are needed for the reaction to form bleach
cold AND dilute (sodium hydroxide)
State how and explain why the attraction between nuclei and outermost electrons in gaseous atoms varies across Period 3.
Attraction between nuclei and electron increases as nuclear charge increases
What is meant by the term average bond enthalpy?
when one mole of bonds is broken
State le Chatelier’s principle.
The (position of a dynamic) equilibrium shifts to minimise (the effect of) any change
State two ways that the use of catalysts helps chemical companies to make their processes more sustainable and less harmful to the environment.
lower temperatures
Less (fossil) fuels burnt
The graph shows that rate of reaction decreases over time.
Explain why, in terms of collision theory.
Less acid concentration
so less frequent collisions
In the experiment the water in the beaker was heated for 5 minutes. The student thought that the experiment could be improved by heating the water for 10 minutes.
Explain whether the accuracy in the student’s calculated value for Δc H may or may not be improved by heating for longer.
Less accurate due to greater heat losses
More accurate due to smaller % uncertainty in temperature change
Explain why organic product is formed in a much greater quantity than the other organic product (major/minor)
Major product forms from most stable carbocation
Carbocation bonded to fewer H bonds
An organic liquid is contaminated with acid. The liquid is placed in a separating funnel.
What is the correct sequence for the operations that follow
Neutralise
Wash
Separate organic layer
Dry
Distil
