PAPER 1 - PRACTICE QUESTIONS Flashcards
compare the structure of a helium atom with a hydrogen atom
- hydrogen has 1 proton helium has 2
- hydrogen has no neutrons and helium has 2
- hydorgen has 1 electron and helium has 2
describe the atomic structure of lithium
- 3 protons in nucleus
- 4 neutrons in nucleus
- 3 electrons which orbit the nucleus in the shells
compare plum pudding with nuclear
- plum: single ball of positive charge // nuclear has a positive nucleus
- plum electrons in random positions // nuclear electrons fixed positions
- plum no nucleus // nuclear does
- plum no neutrons // nuclear has neutrons in nucleus
describe model now used for structure of an atom
- atom has positive protons and neutrons in nucleus
- negative electrons orbit nucleus in shells
- motsly empty space with mass in nucleus
- protons and nuetrons have realtive mass of 1
- electrons have a mass <1
why is potassium more reactive than lithium
- both in group 1
- go down group atoms get bigger
- outer electron is further away from nucleus so weaker attraction
- easier to lose electron
what changes did Mendeleev make to the periodic table
left gaps for new discoveries so that the properties fitted with others in the same group
explain the arrangement of the first 20 elements in todays periodic table
- order of their atomic number
- elements in same group have same number of electrons in outer shell
why was Mendeleev periodic table accepted over time
- new elements fitted into the gaps that he predicted
what happens to lithium and chlorine atoms when they react to form lithium chloride
- lithium loses 1 electron to form a 1+ ion
- chlorine gains 1 electron to form 1- ion
calculate the concentration od hydrochloric acid when it contains 3.2g of hydrogen chloride in 50cm^3
50/1000 = 0.05dm^3
3.2/0.05 = 64
==== 64g/dm^3
what would you observe when metal is added to an acid
- bubbles because hydrogen gas is produced
- container to get warm - exothermic reaction
- metal disappear - making a salt which would dissolve
what happens when any acid reacts with any alkali
- H+ from acid and OH- from alkali react to make water
- neutralisation
acid + base –> salt + water
explain what forms at the cathode during electrolysis of copper sulphate
- copper forms because the copper ions have a positive charge
- copper gains electrons and is reduced to form copper
explain what forms at the anode during electrolysis of copper sulphate
- oxygen forms at the negative electrode because negative charge
- oxygen loses electrons and oxidised to form oxygen
- reacts with carbon in the electrolyte and forms co2
what happens at anode
- anode is positive so attracts negative ions
- these negative ions loses electrons and oxidised
- if solution has NO HALIDE ION then oxygen is produce
- oxygen then reacts with carbon in solution - co2 produced
what happens at cathode
- cathode is negative so attracts positive ions
- these positive ions gain electrons and are reduced
- if metal more reactive than hydrogen then hydrogen forms instead
why are electrodes replaced when o2 forms during electrolysis
- negative ions attracted to positive electrode made of carbon
- oxygen reacts with carbon - co2 - due to high temps
- overtime it wears away
explain when hydrogen gas forms at the negative electrode
- water breaks down during aq electrolysis to form H+ ions
- if metal produced is less reactive then hydrogen then the hydrogen is discharged at the negative electrode
- here they gain electrons and form hydrogen molecules
explain how halogen gases can be formed at the positive electrode
- halide ions are negatively charged so attracted to positive electrode
- halide lose electrons and form molecules
- eg chlorine ions will form chlorine gas
when an acid is added to an alkali there is an energy change. explain this change
- neutralisation reaction
- this is exothermic
- therefore heat released to the surroundings
- energy of products less than energy of reactants
define activation energy
min amount of energy particles must have to react when reacting particles collide with each other
describe what happens when a magneisum atom recats with 2 chlorine atoms - ionic compound
- mag loses 2 electrons to get a mg2+
- chlorines gain an electron each to get cl-
- opposite charges attract - ionic compound - mgcl2
