deck_16581369 (1) Flashcards
Describe the plum pudding model of the atom.
a ball of positive charge
with (negative) electrons
embedded
Atoms contain electrons, neutrons and protons.
Write these three particles in order of their discovery.
(earliest) electrons
protons
(latest) neutrons
Predict the number of outer shell electrons in an atom of tennessine.
Give one reason for your answer.
Use the periodic table.
(number of outer shell electrons)
7
(reason) (tennessine is in)
Group 7
Tennessine was first identified by a small group of scientists in 2010.
Suggest one reason why tennessine was not accepted as a new element by other
scientists until 2015.
(time needed for) peer review
How do the results show that dissolving ammonium nitrate in water is endothermic?
temperature decreased
The student recorded the mean lowest temperature of the solution for 8.0 g of
ammonium nitrate as 16.5 ± 0.3 ºC.
Explain why the student included ± 0.3 ºC after the mean lowest temperature.
(0.3 °C) is the uncertainty
(because 0.3 °C) is the range
about the mean value
Name two other substances that can each be reacted with a dilute acid to make
zinc chloride.
Do not refer to zinc carbonate in your answer.
any two from:
* zinc
* zinc oxide
* zinc hydroxide
Plan a method to make pure, dry crystals of zinc chloride from zinc carbonate and a
dilute acid.
- use zinc carbonate and hydrochloric acid
- add zinc carbonate to the (hydrochloric) acid
- in a beaker
- stir
- continue adding until the zinc carbonate is in excess
- shown by excess solid
- and no more effervescence
- filter (the reaction mixture)
- to remove the excess zinc carbonate
- heat the solution
- using a water bath or electric heater
- to crystallisation point
- leave the solution to crystallise
- pat crystals dry with filter paper
The reaction between hydrogen and chlorine is exothermic.
Explain why this reaction releases energy to the surroundings
energy is needed to break
bonds
and
energy is released when bonds
form
(and) the energy released is
greater than the energy needed
Methane is a gas at room temperature but poly(ethene) is a solid at room
temperature.
Explain why methane and poly(ethene) exist in different states at room temperature.
(methane)
methane has (much) smaller
molecules
(so) has weaker intermolecular
forces
(so the intermolecular forces)
need less energy to overcome
(so) the boiling / melting point is
lower (and methane is a gas)
OR
(poly(ethene))
poly(ethene) has (much) larger
molecules (1)
(so) has stronger intermolecular
forces (1)
(so the intermolecular forces)
need more energy to break (1)
(so) the melting / boiling point is
higher (and poly(ethene) is a
solid) (1)
Ethanoic acid is a weak acid.
What is meant by ‘weak acid’?
Answer in terms of ionisation.
(the acid is only) partially ionised
(in aqueous solution)
The concentration of an acid can be measured in mol/dm3.
Which combination of changes increases the concentration of an acid?
the mass of acid dissolved is
doubled and the volume of the
solution is halved
Which element has atoms that have the same electronic structure as the chloride ion?
Use the periodic table.
argon / Ar
Evaluate the use of aluminium, copper and silver for the types of electrical wires
shown in Figure 6.
- silver is the best electrical conductor
- aluminium is the least dense
- aluminium is the least expensive
- copper is a better conductor than aluminium
or
copper is almost as good a conductor as silver - copper is much less expensive than silver
- overhead power cables need a low density metal
- wiring in homes needs to be affordable
- printed circuit boards only require small amounts of material
judgements
* use aluminium for overhead wires because of aluminium’s
low density and/or lower cost
- use copper for domestic wiring because copper is a very good
conductor and not too expensive - use silver only for small uses such as circuit boards due to high
cost - copper is a good compromise between electrical conductivity and
cost
Describe how metals conduct electricity.
(metals have) delocalised
electrons
the electrons carry (electrical)
charge
the electrons move through the
structure / metal
Electrical wires are usually made of pure metals and not alloys. This is because pure
metals are better electrical conductors.
Suggest why alloys do not conduct electricity as well as pure metals.
Answer in terms of structure and bonding.
in alloys different sized atoms
distort the layers / structure
(so) the movement of
(delocalised) electrons is
restricted
Cryolite contains Na+ ions as well as Al3+ ions.
Suggest one reason why sodium is not a product of the electrolysis.
sodium is more reactive than
aluminium
Hydrogen was produced at the negative electrode and oxygen was produced at the
positive electrode.
Explain how oxygen was produced from water during the electrolysis of this
aqueous solution.
water (molecules) break down
(to) produce (H+ and) OH− (ions)
(so) OH− (ions) are attracted /
move to the positive electrode
(where) OH− (ions) are
discharged / oxidised to give
oxygen (molecules)
The student compared the volumes of the two gases collected.
How can the student change the apparatus in Figure 7 to compare the volumes of the
two gases produced more accurately?
Give one reason for your answer.
(change)
use measuring cylinders
(instead of test tubes)
(reason)
because there is a scale (on the
measuring cylinders)
Argon has the atomic number 18
Explain why argon does not form compounds.
Answer in terms of electrons.
(atoms of) argon have a stable
arrangement of electrons
(so) argon (atoms) do not share
/ transfer electrons
Phosphorus (P) is the element below nitrogen in the periodic table.
Predict the formula of the compound formed between phosphorus and hydrogen.
PH3
Tellurium is the element with atomic number 52
Predict whether tellurium reacts with metals.
Explain your answer.
Answer in terms of the position of tellurium in the periodic table.
yes, because tellurium is
towards the right of the periodic
table
(so) tellurium is a non-metal
OR
yes, because tellurium is in the
same group as oxygen / sulfur
(1)
(and) oxygen / sulfur will react
with metals (1)
OR
no, because tellurium is towards
the bottom of the periodic table
(1)
(so) tellurium is a metal (1)
OR
cannot predict as tellurium is
towards the bottom and to the
right of the periodic table (1)
(so) don’t know whether
tellurium is a metal or non-metal
(1)
Suggest two observations that could be made when barium reacts with
hydrochloric acid.
any two from:
* effervescence / fizzing /
bubbles
* barium disappears
* forms a colourless solution
* temperature increases
Which substance in the equation is reduced?
Give one reason for your answer.
Answer in terms of oxygen.
(substance reduced) Fe2O3
(reason)
(Fe2O3) loses oxygen
The ionic equation for Reaction 1 is:
A + 2 B+ → 2 B + A2+
Why is this a redox reaction?
A loses electrons and B+ gains
electrons
The nitrate ion has the formula NO3–
Which of the four metals could be aluminium?
Explain your answer.
(metal) C
(explanation) aluminium forms
ions with a charge 3+
(so) 3 nitrate ions are needed
for 1 aluminium ion
Self-cleaning windows are coated with a layer of nanoparticles of titanium dioxide.
Titanium dioxide:
* helps sunlight break down dirt particles
* attracts water, so dirt is washed away by rain.
Nanoparticles of titanium dioxide are used instead of fine particles of titanium dioxide
for coating self-cleaning windows.
Suggest two reasons why.
(nanoparticles)
any two from:
* have a higher surface area to
volume ratio
* less (material) needed (for the
same effect)
* more light gets through
