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AP® Chemistry flashcards Periodic Table flashcards
1
Q

Separate unlabelled solid samples of three anhydrous sodium compounds are
provided for a student to identify.
These compounds are known to be sodium carbonate, sodium fluoride and
sodium chloride but it is not known which sample is which.
Outline a logical sequence of test-tube reactions that the student could carry out to
identify each of these compounds.
Include the observations the student would expect to make.
Give equations, including state symbols, for any reactions that would take place.

A

a Add named acid to all 3
1b Add water / make into a solution
1c Add AgNO3
2a Na2CO3 will fizz with acid
2b NaCl gives white ppt with AgNO3
2c NaF shows no (visible) change / no ppt

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2
Q

Silicon tetrafluoride (SiF4) is a tetrahedral molecule.
Deduce the type of intermolecular forces in SiF4
Explain how this type of intermolecular force arises and why no other type of
intermolecular force exists in a sample of SiF4

A

Van der Waals forces
one molecule induces dipole in
neighbouring/another/nearby molecule
symmetrical molecule / dipoles cancel

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3
Q

Suggest how the students’ method, and the analysis of the results, could be
improved in order to determine a more accurate value for the enthalpy of
reaction.
Justify your suggestions.

A

1a Insulate the beaker or use a polystyrene cup or a
lid
1b To reduce heat loss
2a Record the temperature for a suitable time before
adding the metal
2b To establish an accurate initial temperature
OR
2c Record temperature values at regular time intervals
2d To plot
Extrapolate the cooling back to the point of addition

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4
Q

Explain how permanent dipole-dipole forces arise between hydrogen chloride
molecules.

A

Difference in electronegativity leads to bond polarity
there is an attraction between ∂+ on one molecule and ∂- on
another

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5
Q

state one advantage of using a conical flask rather than a beaker for the titration

A

less chance of splashing

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6
Q

explain why the melting point of magnesium is higher vthan the nelting point of sodium

A

-mg2+ is smaller
-strong eelctrostatic forced between mg+and sea delocalised electrons

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7
Q

observation when dilute aqeuous naoh with mgcl2 and bacl2

A

white ppt
no observation

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8
Q

suggest why an excess of silver nitrate is used

A

to ensure thta all the halide ions are remooved fro the solution

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9
Q

observation when mg reacts with steam

A

bright light
mg+h20- mgo+h20

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10
Q

describe a further test to show whether solution c contains chloride or bromide ions

A

-dilute ammonia sol
-chlorate ions present then ti wiuld dissolve
-bromide. would nit

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11
Q

explain how forces arise between molecules of chlorine

A

-spontaneous movement of electrons in one molecule
-induces dipole in neighbouring molecules
-electropos and elecroneg temporayr attraction

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12
Q

rinsing buretter w deionised water before filling with naoh
what affevt

A

titre value would inc bc naoh more dilutr

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13
Q

suggest in terms of the intermolecular forces for eaach compound why cbr4 has a higher bp than chbr3

A

-vdw between cbr4 stronger than vdw and indcued dipole in chbr3

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14
Q

desrcibe a series of tests that the student can use to show that solution c. contains ammonia sulfate

A

test with Ba(NO3)2
produces a white precipitate
test with NaOH and heat
hold damp pH paper over the test tube which will turn blue

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15
Q

explain why this air bubble inc the final burette reading of the rough titration

A

solution will fill gap

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16
Q

during the titration the studnet washed the sinide of the concial flask with some distilles water

suggest why this washing does not give an incorect result

A

doesn’t change the number of moles

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17
Q

another student required to make up 250cm3 of an aqueous solution thay contains a knwon mass of MHCO3. The student apparatus and practical details that the student shouldt prepare the solution

A

1)weigh sample bottle containing the solid on a balance
2)transfer to beaker and reweigh sample bottle
3)record diff in mass
4)add distilled water\5)stir
6)until all solid has dissolves
7)transfer to volumetric flask
8)make up 250cm3 and mark w water
9)invert

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18
Q

a solution of sdoium chlorate was added to colourless solution of potassium iodied suggest what is observed

A

-brwon
-due to iodine being oxidsed

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19
Q

why uv used in propagation

A

provides energy to break (covalent) bond in chlorine / Cl2 or
to form chlorine free radicals

20
Q

importance of % yield

A

idea of getting as much product as possible in the reaction /
idea of efficient conversion of reactants to products

21
Q

importance of % atom economy

A

idea of maximising the mass of reactants / atoms that ends up
in desired product or

22
Q

explain the differences between structural isomerisms and stereoisomerism

A

structural isomers = molecules with same
molecular formula but different structure
1b stereoisomers = molecules with same
structural formula but different
arrangement of atoms in space

Stereoisomers
2a lack of rotation around C=C
2b structures of E- and Z-but-2-ene
2c correct identity of E and Z isomers

Structural isomers
3a different C chain, e.g. methylpropene &
but-1-ene / but-2-ene
3b different position of functional group e.g.
but-1-ene & but-2-ene
3c different functional group, e.g.
cyclobutane & but-1-ene / but-2-ene /
methylpropene

23
Q

ethanedioic acid is formed by the oxidation of ethane -1 2-diol
suitable reagent and conditions

A

conc sulfuric acid
reflux

24
Q

Which statement is correct about thermal cracking?
[1 mark]
A A pressure between 100 and 200 kPa is used.

B Aromatic hydrocarbons are the major products.

C C–C bonds are broken.

D Zeolite catalysts are used.

A

c

25
Q

Which statement is not correct about ozone?
[1 mark]
A It absorbs harmful ultraviolet radiation in the upper atmosphere.
B It decomposes to form oxygen.
C Its decomposition is catalysed by chlorine molecules.
D Ozone holes are regions of the upper atmosphere where there
is a reduced concentration of ozone.

A

c

26
Q

Which can be used to distinguish between these two compounds?
(CH3)2CHCH2CHO and (CH3)3CCHO
[1 mark]
A Acidified potassium dichromate(VI)
B Fingerprint region of infrared spectrum
C Mr value in high resolution mass spectrometry
D Tollens’ reagent

A

b

27
Q

An excess of methane reacts with chlorine in the presence of ultraviolet radiation.
What are the main products of this reaction?
[1 mark]
A CCl4 and H2
B CCl4 and HCl
C CH3Cl and H2
D CH3Cl and HCl

A

d

28
Q

Which statement is correct about the production and use of ethanol as a biofuel?
[1 mark]
A Biofuel ethanol is produced by the fermentation of glucose in the
presence of yeast and air.
B Biofuel ethanol is purified by fractional distillation.
C No carbon dioxide is released when biofuel ethanol is burned.
D Biofuel ethanol burns with a cleaner flame than ethanol made by
hydration of ethene.

A

b

29
Q

Which statement about the molecules in a sample of a gas is correct?
[1 mark]
A At a given temperature they all move at the same speed.
B At a given temperature their average kinetic energy is constant.
C As temperature increases, there are more molecules with the
most probable energy.
D As temperature decreases, there are fewer molecules with the
mean energy

A

b

30
Q

highest ionisation energy in group 3

A

argon

31
Q

products of mg and steam

A

mgo
h2
bright white light
white powder

32
Q

least soluble group 2 sulphate and what’s it used for

A

baso4
x rays

33
Q

diference in cf4 and xef4

A

square planar- 90,4 bp , 2lp ,lone pairs repel more than bonding pairs
tetrahedral-109.5,electrons pair repel equally 4bp

34
Q

similarity and difference in reactions between sulphuric acid and sodium bromide

A

form h halides
br redox

35
Q

meaning of electron impact ionisation

A

fired at high energy electrons to knock of an electron

36
Q

fraction meaning

A

mixture of compounds with similar bp

37
Q

carbon neutral

A

no net co2 emissions

38
Q

why iodobutane faster reaction than bromobutane

A

c-i weaker c-br

39
Q

why major rpdocut more than minor

A

-primary ,secondary structure , more stable carbocation, more electrons releasing alkyl group

40
Q

why c cl bonds polar

A

difference in electronegativity

41
Q

why molecules non [olar

A

symmetrical
dipoles cancel each other out

42
Q

why tetrachlromethane high bp than di

A

-stronger vow than vow and induced dipole
-more electrons

43
Q

explain why water should enter the condenser at the bottom and not top

A

ending condenser fills with water
-condenser cooler

44
Q

Compounds A, B and C all have the molecular formula C5H10
A and B decolourise bromine water but C does not.
B exists as two stereoisomers but A does not show stereoisomerism.
Use this information to deduce a possible structure for each of compounds
A, B and C and explain your deductions.
State the meaning of the term stereoisomers and explain how they arise in
compound B.

A

1a states that A & B are unsaturated / do contain C=C / alkenes (this can be
obtained from the structures)
1b as they decolourise bromine water
1c states that C is saturated / does not contain C=C / is (cyclo)alkane (this can be
obtained from the structures)
1d as it does not decolourise bromine water

suggests suitable name/structure for A
 pent-1-ene,

B = pent-2-ene

suggests a suitable name/structure of C (cyclopentane

explains what stereoisomerism is in terms of molecules with the same structural
formula but a different arrangement of atoms/bonds/groups in space
3b explains how it arises by discussing that C=C cannot rotate

45
Q

Suggest one reason, other than the use of mean bond enthalpies, why a value fo

A

alkane is not gaseous

46
Q

The student used a wash bottle containing deionised water when approaching the
end-point to rinse the inside of the conical flask.
Explain why this improved the accuracy of the titration

A

Idea that it ensures all ethanedioic acid / acid / sodium hydroxide /
alkali / reactants are in the mixture / solution / reaction

47
Q

When 1-bromo-2-methylpropane reacts with hot, concentrated ethanolic
potassium hydroxide rather than dilute aqueous sodium hydroxide, a different
product is formed.
Name this organic product and name the mechanism for this reaction.

A

methyl propene

chem (29 decks)

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