Chemistry 2011 — EUEE past paper

Physical Constants
Constant	Symbol	Value
Gas constant	$R$	$8.314\ \mathrm{J\,mol^{-1}\,K^{-1}} = 0.0821\ \mathrm{L\text{-}atm\,mol^{-1}\,K^{-1}}$
Avogadro's number	$N_A$	$6.023\times10^{23}\ \mathrm{mol^{-1}}$
Plank's constant	$h$	$6.626\times10^{-34}\ \mathrm{J\,s^{-1}}$
Electron volt	$\mathrm{eV}$	$1\ \mathrm{eV} = 1.602\times10^{-18}\ \mathrm{J}$
Speed of light	$c$	$2.9979\times10^{8}\ \mathrm{m\,s^{-1}}$
Faraday's constant	$F$	$96500\ \mathrm{C\,mol^{-1}}$
Charge of 1 mole of electrons		$96500\ \mathrm{C}$

SI Units and conversion factors
Constant	Symbol	Value
Ton	$\mathrm{ton}$	$1\ \mathrm{ton} = 907.185\ \mathrm{kg}$
Metric ton	$\mathrm{t}$	$1\ \text{metric ton} = 1000\ \mathrm{kg}$
Angstrom	$\text{\AA}$	$1\ \text{Å} = 10^{-10}\ \mathrm{m}$
Litre-atmosphere	$\mathrm{L\text{-}atm}$	$1\ \mathrm{L\text{-}atm} = 101.3\ \mathrm{J}$
Coulomb	$C$	$\mathrm{Coulombs} = \mathrm{amperes}\times\mathrm{seconds}$

01

When

\ce{Na2CrO4}

solution is acidified, which of the following is formed?

A. $\ce{Cr}$ (metal)
B. $\ce{Cr2O3}$
C. $\ce{Cr2O7^2-}$
D. $\ce{CrO4^2-}$

Show answer

AnswerC $\ce{Cr2O7^2-}$

Acidifying a chromate solution shifts the chromate–dichromate equilibrium toward dichromate, because H+ is consumed on that side.

\ce{2CrO4^2- + 2H+ <=> Cr2O7^2- + H2O}

Adding acid drives the equilibrium right, so the yellow

\ce{CrO4^2-}

converts to orange

\ce{Cr2O7^2-}

.

Chemical and phase equilibrium · G11 U5

02

What makes the phosphorus cycle different from the carbon and nitrogen cycles?

A.Carbon and nitrogen are found in the atmosphere in the gaseous state.
B.Carbon and nitrogen are released at lower rate compared to phosphate salts.
C.Phosphorus salts are released at higher rate compared to carbon and nitrogen cycles.
D.Phosphorus is found in the atmosphere in the gaseous state.

Show answer

AnswerACarbon and nitrogen are found in the atmosphere in the gaseous state.

Carbon and nitrogen each have a major atmospheric reservoir —

\ce{CO2}

and

\ce{N2}

— that lets them cycle globally through the air. Phosphorus has no stable gaseous form under normal conditions, so it cycles only through rock weathering, soil and water rather than the atmosphere.

Fundamental concepts and stoichiometry · G11 U1

03

Which of the following can function as both a Bronsted-Lowry acid and Bronsted-Lowry base?

A. $\ce{H2SO4}$
B. $\ce{H+}$
C. $\ce{SO4^2-}$
D. $\ce{HSO3-}$

Show answer

AnswerD $\ce{HSO3-}$

A species that can both donate and accept a proton is amphiprotic.

\ce{HSO3-}

fits: it can donate its proton,

\ce{HSO3- <=> H+ + SO3^2-}

or accept one to form

\ce{H2SO3}

, so it acts as both a Bronsted-Lowry acid and base.

\ce{H2SO4}

only donates,

\ce{H+}

only accepts, and

\ce{SO4^2-}

only accepts.

Acid-base equilibrium · G12 U2

04

Which of the four colligative properties arises in systems where there is equilibrium between a liquid solution phase and a second liquid phase?

A.Vapour pressure lowering
B.Osmotic pressure
C.Freezing point depression
D.Boiling point elevation

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AnswerBOsmotic pressure

Vapour pressure lowering, boiling point elevation and freezing point depression are each an equilibrium between the liquid solution and its vapour or solid phase. Osmotic pressure is the odd one out: it is the pressure that balances the chemical potential between a solution and pure solvent across a membrane, i.e. an equilibrium between two liquid phases.

Solutions · G12 U1

05

Acetylsalicylic acid (aspirin) has the structural formula (shown). Which functional group (groups) is (are) present in aspirin?

A.Hydroxyl
B.hydroxyl and carbonyl
C.Carboxyl and ester
D.Carboxyl and acetyl

Show answer

AnswerCCarboxyl and ester

The ring carries a

\ce{-C(=O)OH}

group, a carboxyl, and an adjacent

\ce{-O-C(=O)-CH3}

group, an ester (the acetate linking back to the ring oxygen). Aspirin is therefore built from a carboxylic acid and an ester, not a free hydroxyl or ketone.

Carboxylic acids, esters, fats and oils · G11 U6

Element	H	He	Li	B	C	N	O	F	Ne	Na	P	S	Cl	Ca	Cr	Mn	Fe	Co	Ni	Cu	Zn	Sr	Ag	Cd	I	Pt	Au	Hg
Z	1	2	3	5	6	7	8	9	10	11	15	16	17	20	24	25	26	27	28	29	30	38	47	48	53	78	79	80
A	1.0	4.0	6.9	10.8	12.0	14	16.0	19.0	20.2	22.98	30.97	32.1	35.5	40.1	52.0	54.9	55.9	58.9	58.7	63.5	65.4	87.62	107.9	112.4	126.90	195.1	197.0	200.6

Constants and formulas given with the paper

Questions 1–5