Reflection to chem test Flashcards
Formula of astatine molecule
At2
Describe what you would see when sodium reacts with chlorine
a bright yellow light
white clouds of sodium chloride
Which ion do all acids produce in aqueous solution?
H+
calcium hydroxide + ————acid → calcium chloride + ——–
hydrochloric , water
Explain why carbon nanotubes conduct electricity.
contain delocalised electrons
(so) electrons can move through
the structure / nanotube
Suggest one reason why it costs less to use nanoparticles rather than fine particles in
suncreams.
greater surface area (to
volume ratio)
Define mass number
total neutrons and protons
Give one limitation of using a dot and cross diagram to represent an ammonia
molecule.
It does not show how the atoms are arranged in space.
Evidence from the alpha particle scattering experiment led to a change in the model of
the atom from the plum pudding model.
Explain how
most (alpha) particles passed
(straight) through (the gold foil)
(so) most of the atom is empty
space
some (alpha) particles were
deflected / reflected
(so) the atom has a (positively)
charged nucleus / centre
Explain why ammonia has a low boiling point.
You should refer to structure and bonding in your answer.
(ammonia has) weak
intermolecular bonds
little energy is needed
to break the intermolecular
bonds
(ammonia has) a simple
molecular (structure)
Suggest two control variables used in this investigation.
- temperature
- concentration of electrolyte
order reactivity
cobalt
copper
magnesium
nickel
silver
tin
)magnesium
cobalt
nickel
tin
copper
silver
Justify your order of reactivity.
most reactive (metal)
has the highest voltage
Which of the following pairs of metals would produce the greatest voltage when used
as the electrodes in the cell?
Magnesium and tin
Hydrogen fuel cells can be used to power different forms of transport. Suggest why.
(in a fuel cell) hydrogen is
oxidised (to produce water)
water is produced / released as
gas / vapour / steam
Explain why a mixture is used as the electrolyte instead of using only
aluminium oxide.
mixture has a lower melting
point (than aluminium oxide)
(so) less energy needed
What happens at the negative electrode during the production of aluminium?
aluminium ions gain electrons
Complete the balanced half-equation for the process at the positive electrod
2O2-→ O2 + 4e-
Explain why the positive electrode must be continually replaced.
the electrode reacts with oxygen
the electrode is carbon /
graphite
(so) carbon dioxide is produced
Explain why sodium chloride solution cannot be used as the electrolyte to produce
sodium metal
hydrogen (gas) would be
produced (instead of sodium)
(because) sodium is more
reactive than hydrogen
Suggest one reason why step 8 is needed.
to make sure all of the oxide (of
copper) has reacted
Explain why the excess hydrogen must be burned off.
hydrogen is explosive
What happens at the negative electrode during the production of aluminium?
Aluminium atoms gain electrons
Number of moles=
Mass(g)/relative atomic mass (Ar)
What is relative atomic mass
Protons+neutrons
Density (g/cm3)
=mass (g) /volume (cm3)
1 cm3=
0.001dm3
1000cm3
1dm3
Explain why the reaction between ammonia and oxygen is exothermic.
the products have (kJ) less energy than the reactants
(so) energy is released (to the surroundings)
