Mock Prep: Questions You Got Wrong Flashcards by emaan anwer

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

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Give a property of hydrogen that makes it suitable for an airship

Low density

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Explain why helium is used instead of hydrogen in airships

Because helium is inert, whereas hydrogen is flammable

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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

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Explain how graphite can conduct electricity

It has delocalized electrons
which are free to flow
Throughout the structure
And conduct electricity

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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)

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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

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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

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Balance the equation:
C2H4 + HCL + 02 —-) C2H4Cl2 + H20

2…4…1 —-)2…2

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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.

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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

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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

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Write the chemical reaction of when carbon dioxide turns limewater cloudy

CO2(g) + Ca(OH) aq—-) CaCO3(s) + H2O(l)

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Explain how you know an endothermic reaction has taken place

Temperature of reaction decrease
As energy is taken in FROM surrounding

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Equation for enthalpy change:

Molar enthalpy change= heat energy change(kj)/ number of moles of that substance (mol)

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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

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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

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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

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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

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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

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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

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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

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What color is iodine

Grey solid

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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