For parts (a) – (m), write the answer on the line provided. Each part is worth 1 mark.

(a)       fo(N)s__o_lid

(b)       Name a state change that is exothermic freezing/condensation/deposition

(f)        The mineral asbestos has a typical formula Ca3Mg5(Si4O11)2(OH)2 .

How many atoms are represented in this formula?

(g)       i(I)b(e)f w(ms)h(o)ne___ut__r_on___s_

(h)       Write the symbol of the ion that has 7 protons and 10 electrons

(i)        What is the maximum number of electrons that can 2

(j)        What shape is an s orbital.                                                                    __s__p_he___ri_ca___l_

(k)       How many valence electrons does an atom of selenium, Se, 6

_____

(m)      Write the formula of phosphorus pentachloride. P__C_l5

(n)       (1 mark)  Explain briefly the difference between a physical change and a chemical change.

Same substance present in physical change; different substance(s) formed in chemical change.

(o)       (1 mark)  Define the term “mixture” .

A combination of 2 or more substances in which each substance retains its own chemical identity.

(p)        (1 mark)   Explain briefly why the total mass of the products equals the total mass of the

reactants in a chemical reaction.

A chemical reaction involves only rearrangement of atoms so no extra atoms added/removed (law of conservation of mass).

(q)       Aluminium oxide is a white solid used as an abrasive in toothpaste.

(i)        (1½ marks)  Circle the word in brackets that correctly completes the sentence.

Aluminium oxide is a/an ( ionic / molecular ) compound.

Justify your choice.

contains ion from metal and ion from non-metal

(ii)       (1 mark)  Write the formula for aluminium oxide. ____Al2O3___

The reaction of aluminium metal with oxygen that forms aluminium oxide as the product is classified as a redox reaction.

(iii)      (1 mark) Circle the words in brackets that correctly complete the following sentence.

When aluminium reacts with oxygen to form aluminium oxide, aluminium ( gains / loses )

electrons and is referred to as the ( reductant / oxidant ).

(r)        (1½ marks)  Complete the following sentence about a 46Ca atom.

This atom has _20____ protons, _26____ neutrons and 2__0__ electrons.

(s)        (1 mark)   Write the  complete  electron  configuration  in s, p, d notation  of an  atom  of

phosphorus, P.

(t)         (1 mark)   Explain briefly why members of group 2 of the periodic table exhibit similar

chemical properties.

All group 2 elements possess same number of valence electrons; possess similar electron configurations; all have 2 outer electrons.

(u)        (1 mark) When water is added to silicon tetrachloride, SiCl4, solid silicon dioxide, SiO2, and

hydrogen chloride gas are produced. The equation for this reaction is shown below but is not

balanced. Write on the lines any coefficients required to balance the equation. ___ SiCl4(l)   + 2___ H2O(l)    →    ___ SiO2(s)   +    _4__HCl(g)

(v)       (1 mark)  Explain briefly why the noble gases are very stable chemically.

Possess full valence shells.

Question 2 (15 marks in total)

(a)      The reaction between potassium super oxide, KO2 , and CO2  is used as a source of O2  and

absorber of CO2 in self-contained breathing equipment used by rescue workers. The relevant chemical equation for this process is given below.

4KO2(s)  +  2CO2(g) ——→ 2K2CO3(s)  +  3O2(g)

(i)     (1 mark) Show that the molar mass of K2CO3 is 138.19 g mol- 1

M(K2CO3) = 2 × 39.09 + 12.01 + 3 × 16.0 = 138.19 g mol-1

(ii)       (2 marks) In a breathing equipment, 30 g of potassium super oxide is used. Calculate

the amount in moles of potassium super oxide used in this equipment. M(KO2) =71.09 g mol- 1

n(KO2) = = − 1 = 0.422 mol

(iii)      (2 marks) Calculate the mass of O2 produced in this equipment.

= = × 3 = 0. 3165 mol

M(O2) = 0.3165 mol × 32.0 g mol-1 = 10.128 g = 10.1 g

(iv)      (2  marks) If a person breathes out 8.9 g of CO2 to react with 30.0 g of potassium

super oxide determine which chemical is the limiting reactant in this equipment. Show your working.

n (CO2 ) = = −1 = 0. 2022 mol

For all KO2(0.422 mol) we need n(CO2) = × 2 = 0. 211 mol We have only 0.2022 mol of CO2 . So the limiting reactant is CO2 .

(v)       (2  marks) Use your answer to (iv) above to calculate the mass of K2CO3 produced in this equipment.

n(K2CO3) = n(CO2) = 0.2022 mol

m(K2CO3) 0.2022 mol × 138.19 g mol-1 = 27.9 g

(vi)      (2 marks) A student dissolves 30.5 g of K2CO3 in 250 mL of deionised water.

Calculate the concentration of K+ ions in the solution.

n(K2CO3) = −1 = 0. 2207 mol

C(K2CO3) = = 0. 8828 mol L− 1

C(K+) = 2 × 0.8828 mol L-1 = 1.7656 mol L-1 = 1.77 mol L-1

(vii)     (4 marks) Some sulfuric acid is spilled on a lab bench. You can neutralize the acid by

sprinkling sodium bicarbonate on it.

2NaHCO3(s)  +  H2 SO4(aq) —→ Na2 SO4(aq)  + 2H2O(l)  +  2CO2(g)

Sodium bicarbonate is added until the fizzing due to the formation of CO2(g) stops.

If 27.5 mL of 6 mol L- 1 H2 SO4 was spilled, calculate the minimum mass of NaHCO3 that must be added to the spill to neutralize the acid.

M(NaHCO3 = 84.008 g mol- 1

n(H2SO4) = 6 mol L-1 × 27.5 × 10-3 L = 0.165 mol

n(NaHCO3) = 2 × 0.165 mol = 0.33 mol

m(NaHCO3) = 0.33 mol × 84.008 g mol-1 = 27.7 g

QUESTION 3: (10 marks TOTAL)

(a)     (i) (2 marks) School of chemical sciences has the abbreviation SCS. In chemistry this is how the atoms are bonded in carbon disulphide. Draw the Lewis structure for CS2 .

S C S

(ii)  (2 marks) Predict the shape that describes the arrangement of atoms about the C atom in

CS2 . Justify your answer.

Shape of CS2 Linear____________

Reason for the shape

There are 2 areas of electron domains on central atom. Both are bonding. To minimise repulsion bonds organise in linear shape.

(b)    (i) (2 marks) Draw the Lewis structure for sulfur dichloride, SCl2 .

S

Cl                  Cl

(ii) (2 marks) Predict the shape that describes the arrangement of atoms about the S in SCl2 .

Justify your answer.

Shape of SCl2 ___ bent ____

Reason for the shape

There are 4 areas of electron domains on central atom. Two are bonding and two are non bonding. To minimise repulsion these are directed towards the corners of a tetrahedron. Only bonding domains contribute to the shape.

(c)       (2 marks) Give the bond angles for:

(i)        S-C-S in CS2                                        _1_80° (ii)       Cl-S-Cl in SCl2 .                      _1_05°

QUESTION 4: ( 10 marks TOTAL)

The questions below relate to compounds A-J in the table below.

(a) (5 marks) The compounds in the table may be used for more than one answer below. Give, in the boxes provided, one compound which:

(b) (1 mark) Draw the line structure of compound D:

QUESTION 5: ( 15 marks TOTAL)

(a) Ibuprofen is an organic compound that is very commonly used as a painkiller and anti-inflammatory.

*

O

OH

ibuprofen

(i) (1 ½ marks) Complete the molecular formula of Ibuprofen: C___H____O____

(ii) ( ½ mark) State the oxygen-containing functional group in ibuprofen:

(iii) ( ½ mark) Is ibuprofen a hydrocarbon?    Yes / No (circle one)

(iv) (1 mark) Ibuprofen is an  aliphatic / aromatic,  saturated  / unsaturated compound.

(circle one) (circle one)

(v) (½ mark) Mark any stereogenic centres on the above structure of ibuprofen with an asterix (*).

(b)  Alkenes like alkene K (shown below) can undergo reactions with H2 in the presence of a catalyst to give alkanes.

(i) (1½ mark) State the catalyst and draw the product of the reaction and the in the boxes

provided:

H2

(ii) (½ mark) This type of reaction is an    addition   /   elimination   /   substitution.

(circle one)

(iii) (1 mark) Can alkene K exist as E/Z isomers?             Yes  /  No (circle one)

Brieflyjustify your answer

No, as one of the C=C carbons has two of the same group (methyl) attached.

(iv) (2 marks) When alkene K reacts with HBr, two possible products are possible, one major and one minor. Give the structures of the two products in the boxes provided and state which is the major and which is the minor.