Wrong Questions - C1 to C3 Flashcards
Why is a reaction endothermic?
- bond breaking is endothermic / bond breaking takes in energy/bond-breaking absorbs energy (1)
bond making is exothermic / bond making gives out energy - bond making releases energy (1)
- more energy taken in than is released / more energy
absorbed than given out (1)
How do you know if a substance is an enzyme?
- it removes organic materials only such as food and blood
- not paint etc.
How do you test for unsaturated fats?
- test - add bromine (water) (
- result - idea that bromine water loses its colour (1) – this mark is dependent on the correct reagent or a
near miss e.g. bromide
Describe the process of crystallisation:
- solution heated until saturated (no more solute can be dissolved at that temp)
- crystals form
- lower heat = more crystals form as solubility increases
- use filtration to separate the crystals and pat dry
What is the empirical formula?
- the simplest whole-number ratio of atoms each element in a compound has
How does the melting point change in impure and pure substances?
- m.p. of impure is less than pure
- b.p. of pure is less than impure
What is an allotrope?
- diff form of element in the same state and with a different atomic arrangement
What makes something malleable?
- particles can easily change position in a lattice
What makes something brittle?
- substance can crack if an external force is applied
What is a disadvantage of low percentage yield?
- waste a lot of starting material/wastes reactants (1)
How did Geiger and Marsden’s experiment tell us about the atomic structure?
- Fired alpha particles at gold foil (1)
- Geiger and Marsden’s experiment gave unexpected
results / some alpha particles rebounded (1) - led to theory of nuclear atom / idea of atoms having
a nucleus (1)
What’s a disadvantage of using universal indicator?
- does not give a sudden colour change / colour
changes slowly / continually changes colour / (
Why should scientists work in groups?
- can share ideas / have different views (1)
- can evaluate ideas / check results / can compare
results (1) - can collect more evidence (in a shorter time) / more
productive / can do more approaches / can work
faster / more ideas can be tested (1) - can share cost of research (1)
Describe endothermic reactions:
- temp decreases
- heat energy is taken from surroundings
- bond breaking is endothermic
- energy used to break bonds is more than the energy released by forming bonds
- if not enough energy, the reaction may not start (activation energy)
- positive energy change
Describe exothermic reactions:
- temp increases
- heat energy is given to surroundings
- bond forming is endothermic
- energy released by forming bonds is greater than the energy needed to break them
- if not enough energy, the reaction may not start (activation energy) = activation energy
- negative energy change
How is a pH meter used?
- calibrate
- adjust the reading to pH of the buffer solution
- wash prove
- place probe in a test solution
- read the reading
How can you make soluble salts using acid/ alkali reactions?
- can’t add excess alkali to acid and filter out what’s left as the salt is soluble and would be contaminated with excess alkali
- thus need to titrate the solution with an indicator
- carry out reaction with exactly the right proportions, without indicator as you now know exact volumes = salt is not contaminated
- slowly evaporate water and leave the solution to crystallise and filter off solid and dry
- SALT MADE IS AQUEOUS
How can you make soluble salts using an acid and an insoluble reactant?
- need to pick and acid, and a metal/ insoluble base (oxides/hydroxides of metals)
- add an excess of base to acid = soluble salt and water - finished when excess solid sinks to bottom (may need to heat mixture)
- filter of excess solid to get salt and water solution
- heat solution to evaporate water and leave concentrated solution to cool and crystallise
- filter off solid and leave to dry in warm over/desiccator
- SALT MADE IS AQUEOUS
How can you make insoluble salts using a precipitation reaction?
- pick 2 soluble salts
- add a spatula of 1st salt (Lead nitrate) to the test tube and add deionised water to dissolve it - shake and do the same to the 2nd salt (sodium chloride)
- tip 2 solutions into small beaker and stir - salt should precipitate out
- put folded filter paper into funnel and stick in conical flask
- put beaker content into flask and make sure solution doesn’t go over the paper as thus less mass made
- swill beaker with deionized water and tip into funnel
- rinse contents of filter paper with deionized water and scrape lead nitrate into fresh filter paper and leave to dry
- make sure reaction is complete before filtering and dry in desiccator or warm oven (NOT Bunsen Burner)
- SALT MADE IS SOLID
What is a non-inert electrode?
- changes or decomposes into the electrolyte
How does the electrolysis of purification of copper work?
- anode = impure copper - mass decreases as copper dissolves
- cathode = pure copper - mass increases as copper deposited
- electrolyte = copper sulfate - collects impurities
- metal ions from the electrolyte discharge on the surface and metal ions leave the anode to replace discharged ions and decompose to CU2+ ions in the electrolyte till the anode is used up
What happens at the anode in a cell?
- oxidation
- 4OH- –> 02+ 2H20 + 4H+
What are the advantages of a high atom economy?
- more sustainable / make less or no waste products (1)
Why do strong and weak acids both make the same no. of moles of H2?
- they have the same no of moles of metal (e.g. magnesium), which is the limiting reactant
How does an increase in pressure affect the rate of reaction?
- more crowded
- are closer together
- more molecules in the same volume
- number of collisions per second
How does an increase in concentration affect the rate of reaction?
- more crowded
- acid particles are closer together
- more acid particles per unit volume
- more (successful) collisions per second
What is the difference in reaction between sodium and water and sodium and butanol?
- sodium and water makes an alkali and H2
- sodium and butanol makes a salt and H2
Why may the right amount of ester not be made? Is it due to the reaction reaching equilibrium or the reactants running out?
- all acids and alcohols are not used up as the amount of reactants stay the same
- even if it reaches equilibrium, the rate of the forward reaction is equal to the rate of the backward reaction
- reaching equilibrium doesn’t mean reactions stop
Why may sulfuric acid be added in reaction?
- acts as a catalyst to speed up reactions
- lowers the activation energy
What parts of a titration make it more accurate?
- add alkali in conical flask with pipette
- read from meniscus
- drop by drop in the end
- always swril mixture
- when colourless, stop instantly
- repeat three times - the first one is a rough titre
- until concordant titres (within 0.1cm cubed)
Why does gunpowder not react until it’s lit?
- when it’s lit, energy is transferred to it which is the activation energy
- this is needed to break the bonds
What does diatomic mean?
- 2 atoms or pairs of atoms in each molecule
What is the difference between a by-product and a waste product?
by-product/oxygen has another use; ORA(1)
the waste product is thrown away / must be disposed of;
(1)
Why are the relative atomic mass (Mr) of some elements are whole numbers but others aren’t?
- Mr of an element is the average of the mass numbers of all the atoms of that element
- if they only have one isotope - Mr is equal to the mass number to that number of atoms
- but if they have more than one isotope which has different quantities then their average isn’t a whole number
Why is the decrease in mass calculated in electrolysis not the increase?
Because newly deposited copper can flake
off the cathode easily, leading to mass
values that are too small
Why do reaction rates decrease near the end?
- acid particles used up
- so concentration decreases
- less frequent collisions / fewer collisions per second
- so rate decreases/reaction slows down
Why is excess added in neutralisation reactions?
- to make sure the substances react
What is a strong acid?
- completely / fully ionised
- in an aqueous solution or when dissolved in water
Why may a fertiliser cost more than the other?
- more stages
- uses more energy
- uses more raw materials
- takes longer
Compare the plum pudding and the nuclear model:
- both have positive charge, both have (negative) electrons, neither has neutrons
- differences:
plum pudding model:
- ball of positive charge (spread throughout)
- electrons spread throughout (embedded in the ball of positive charge)
- no empty space in the atom
- mass spread throughout
nuclear model:
- positive charge concentrated at the centre
- electrons outside the nucleus
- most of the atom is empty space
- mass concentrated at the centre
