Mock Prep: Questions You Got Wrong Flashcards
Explain two things to ensure when carrying out a chromatography test to test the substances in ink. And explain why
1)baseline should be above the water, so that the inks do not dissolve into the water
2)baseline should be drawn in pencil not pen, otherwise pen could contaminate the results, whereas pencil would not interfer
Give a property of hydrogen that makes it suitable for an airship
Low density
Explain why helium is used instead of hydrogen in airships
Because helium is inert, whereas hydrogen is flammable
State two observations in the displacement reaction between magnesium and copper sulfate:
Blue copper sulfate solution turns colorless as magnesium sulfate is formed
A pink brown solid of copper is formed
Explain how graphite can conduct electricity
It has delocalized electrons
which are free to flow
Throughout the structure
And conduct electricity
Explain why diamond is hard but graphite is soft
Because diamond has a rigid lattice structure whereas
graphite is arranged in layers which can Slide Over each other
(This has nothing to do with the fact that they are both giant covalent substances.giant covalent just means that the atoms can go on an on in the structure, and that there are no molecules)
Difference between simple molecular and giant covalent structures
Simple molecular substances consist of molecules in fixed numbers
But giant covalent have no molecules, just atoms in structures, which can vary in number
State how many carbon atoms each one single atom is joined to, in
Diamond:
Graphite:
Diamond: each carbon atom joined to four other carbon atoms
Graphite: each carbon atom joined to three other carbon atoms
Balance the equation:
C2H4 + HCL + 02 —-) C2H4Cl2 + H20
2…4…1 —-)2…2
When pentane reacts with bromine, give the chemical formula of the two products formed
Bromopentane + hydrogen bromide
C5H11Br + HBr
Remeber that for bromopentane, one atom of hydrogen is replaced therefore it goes from H12 to H11.
Methane is burnt with a Bunsen burner and is connected to a U tube, surrounding by ice. Explain why water collects in the Utube
In the combustion of methane, carbon dioxide and water VAPOUR are formed.
So the gas thus condenses into a liquid
Write the chemical equation of the reaction taht occurs when an excess of carbon dioxide is added to calcium hydroxide
CO2(g)+ CaCO3(s) + H2O(l)—) Ca(HCO3)aq
Write the chemical reaction of when carbon dioxide turns limewater cloudy
CO2(g) + Ca(OH) aq—-) CaCO3(s) + H2O(l)
Explain how you know an endothermic reaction has taken place
Temperature of reaction decrease
As energy is taken in FROM surrounding
Equation for enthalpy change:
Molar enthalpy change= heat energy change(kj)/ number of moles of that substance (mol)
Explain if the enthalpy change is positive or negative for an endothermic reaction
Negative
Because the products have more energy than the reactants
This is because Energy is taken in form the surroundings
When measuring rate of reaction between magnesium and hydrochloric acid, give two reasons why the volume of gas collected may be less than the volume expected
-Some gas may have escaped whilst putting the rubber bung on
-the magnesium may be impure
In the reaction between magnesium and hydrochloric acid, explain why it isn’t necessary to measure the hydrochloric acid with a measuring cylinder
Because the hydrochloric should be in excess so a precise measurement is not required
Explain how a decreased concentration of ions, in the reaction between magnesium and hydrochloric acid, decreases the rate of reaction
-less ions in the same volume
-therefore less frequent successful collisions
-per second
-so rate of reaction decreases
Stage 1 pour 50 cm
3 of dilute sulfuric acid into a beaker
Stage 2 warm the acid using a Bunsen burner
Stage 3 add a small amount of copper(I) oxide to the warm acid and stir the mixture
Stage 4 add further amounts of copper(I) oxide until copper(Il) oxide is in excess
Stage 5 filter the mixture
Stage 6 obtain crystals from the filtrate
Explain why in stage five the mixture is filtered
To remove the Excess solid, which is copper (ii)oxide from the solution,
So that you can obtain the copper (ii) sulfate solution
Explain how you can obtain a pure dry sample of a salt solution 6 marks
1)Heat in an evaporating basin to evaporate SOME of the water
2)keep heating until crystals are formed, which you can test with a glass rod
3) leave to cool,to form proper crystals(bc less soluble in cool temperatures)
4)remove the crystals by filtration
5)dry by leaving in a warm oven , to evaporate rest if the water
6)pat dry with a towel
State what colourless the reaction will turn, when aqeous solution of chlorine reacts with aqeous soltuion of potassium bromide, and why
Turn orange because bromine is displaced by more reactive chlorine
What color is iodine
Grey solid
State five properties that a metal should have to be used as a saucepan
-good conductor of heat
-high density
-High boiling point
-should resist corrosion
-should not react with the food
What is an alloy
a mixture of two or more elements, one of which is a metal
2 reasons why fermentation is done in the absence of air
1) for anaerobic respiration, OTEHRWISE no ethanol can be produced, and instead carbon dioxide and water will be
2)Otehriwse the oxygen will react with the ethanol produced to oxidize it and produce ethanoic acid
State the colour change when potassium dichromate solution is added to ethanol, and explain why
Orange to green (bc of the presence of Cr3+ ions)
How are oxides of nitrogen made in a car engine
The high temperatures of the engine allow nitrogen and oxygen, both in the air to react with each other
When chlorine gas is produced explain a safety precaution and why
Use a fume cupboard , because chlorine gas is poisonous
When using hydrochloric acid, explain a safety precaution and explain why
Wear goggles because acid may be corrosive
iii) Identify a method to separate water from copper(II) sulfate solution
Simple distillation
(Whenever they ask to separate a LIQUID from a solid then it’s simple distillation)
(If its for eg a solid from a liquid then you could use crystallization)
Give three examples of the names of the types of ways to prevent iron form rusting
Sacrificial protection, using a more reactive metal
Barrier methods such as coating in paint or oil
Galvanizing (A COMBINATION OF BOTH METHODS WHICH USES ZINC SPECIFICALLY)
In the reaction to show diffusion, between cotton wool soaked in hydrogen chloride gas and ammonia gas, which side does the ring of ammonium chloride form closest to and why
Forms closest to the hydrogen chloride side
Because ammonia gas travels faster than hydrogen chloride, as it is lighter
So it therefore travels further in the same amount of time
Explain why the diffusion of gases doesn’t occur immediately and requires some moments before
Because gases move in random directions and collide with the air particles first
Give the percentage of argon and of carbon dioxide in the atmosphere
Argon: 0.9%
CO2: 0.04%
In the experiment to find the composition of oxygen in the air using copper, give one reason why the actual value is less than the theoretical value
The gas may not have been left to cool
which can alter the results as gases expand when they are hot
Why can sodium oxide not conduct electricity
An ionic compound so has a fixed lattice structure
Therefore ions can not move
What colour does sodium turn in the flame test
Turns yellow
Write the word equation for the reaction between methane and bromine gas
CH4 + BR2 ——) CH3Br + HBr
What is the name of the reaction between methane and bromine gas under ultraviolet light
Substitute
What colour do alkenes turn in bromine water
Colourless
Give an example of the name of the type of reaction, just for alkenes
Addition reaction
Explain why cotton wool is placed over there reaction between calcium carbonate chips and hydrochloric acid when doing rate of reaction experiments
To stop the acid from splashing out, and so that carbon dioxide gas can escape so that it doesn’t build up and create pressure
Explain why putting a cotton wool over a test tube with calcium carbonate chips and hydrochloric acid improves the accuracy of the results when testing for the rate of reaction
Because it ensures that only the carbon dioxide gas leaves, so that the decrease in mass will only be because of that
Graphite and C60 fullerene contain covalent bonds, but have different structures.
Explain why C60 fullerene has a much lower melting point than graphite. Refer to structure and bonding in your answer
Graphite is a giant covalent substance
So inroder to melt it, covalent bonds must be broken
But c60 fullerene is a simple molecular substance,
So in order to melt it,intermolecular forces of attraction must be broken
So more heat energy is required to break covalent bonds, than intermolecular forces of attraction, which is why fullerene has a lower boiling point
Instead of using a delivery tube, suggest one piece of apparatus that can be used to collect a higher yield of water, and explain how
A condenser
Because then less steam will be lost
Give the word equation of hydration
Ethene + steam —-) ethanol
Give the word equation of hydrogenation:
(For alkenes)
Alkene + hydrogen —-) Alkane
Eg(ethene + hydrogen—-) ethane
When a Carboxylic acid and alcohol react together, the OH is removed from which group and the H form which group
OH from the Carboxylic acid
H from the alcohol
Give the general word equation of the reaction of Alkenes in addition reaction
Bromine + alkene—-) dibromoalkane
State the general word equation when an alcohol reacts with oxygen using an oxidizing agent, and state what else needs to be present
Alcohol + potassium dichromate (iv) —-) ethanoic acid + water
Sulfuric acid must be present
State the general word equation to make an ester
Alcohol + Carboxylic acid —-) ester + water
Name the
ester made from
the acid catalysed
esterification of
CH3CH2CH2COOH and
CH.3OH
Methyl butanoate
Because buatnoic acid and methanol
Addition polymerisation
requires an additive - what’s
its name and role?
Initiator
Speeds up a reaction and gets used up
Apart from perfumes, give one other use of esters in the chemical industry
Flavorings
What does it mean if a compound is volatile
It evaporates easily
Name the ester which has structural formula CH3COOCH2CH3
Ethyl ethanoate
Give the structural formula of butanol
CH3CH2CH2CH2OH
Give the formula for poly(butene)
(C4H8)n
