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Nama:………………………………………… Sekolah:…………………………

25 JUN 2014

Cemerlang kimia

1. Definition

Define:

a. Empirical formula

b. Melting point

c. Neutralization

d. Electrolysis

e. Acid

f. Alkali

g. Proton number

h. Strong alkali

Give the operational definition:

a. Strong acid

2. Manufactured substances in industries

a.

Name the monomer for each of the polimer

Draw the structural formula for each of the monomer

Structural formula of polymer Structural formula of monomer

Polyethene

Polyvinyl Chloride

Polypropene

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b.

Draw the structural formula for each of the monomer

Name the monomer for each of the polimer

Structural formula of polymer Structural formula of monomer

3. Stoichiometry

a. Calculate the mass of magnesium oxide, MgO, which is formed when 1.2 g of

magnesium, Mg, is burnt in oxygen, O2. (RAM; O,16;Mg,24). The chemical equation of

the reaction is as follows: 2Mg + O2 2MgO.

b. What is the volume of carbon dioxide, CO2, released when 10 g of calcium carbonate,

CaCO3, reacts with excess dilute hydrochloric acid, HCl, at room conditions? (RAM; C,12;O,16;Ca,40;

Molar volume: 24 dm3 at room temperature)

c. Calculate the mass of zinc, Zn, reacting with dilute nitric acid, HNO3, if 360 cm3 of

hydrogen, H2, gas is released in this reaction. (RAM: Zn,65; Molar volume: 24 dm3 at room

temperature)

d. The following reaction can be used to prepare copper(II)chloride salt.

CuCO3 + 2HCl CuCl2 + H2O + CO2. Excess copper(II)carbonate is added to react with 50 cm3 of

2.0 moldm-3

hydrochloric acid to form the salt. Calculate the mass of the salt formed.

( RMM CuCl2 ,135 )

4. Chemical bonds

a. Explain the formation of the above mentioned compound. ( 8 points )

Your task is to highlight the important answering key words provided in the following

suggested answer.

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Hydrogen, H atom has the electron arrangement of 1. Chlorine, Cl atom has the electron

arrangement of 2.8.7. Both atoms have the tendency to achieve stable duplet and octet

electron arrangement. As such atom of hydrogen shares its 1 valence electron with 1

valence electron of atom of chlorine. Covalent chemical bond is formed between 1 atom

of hydrogen and 1 atom of chlorine. A molecule is thus produced with many more similar

bonding formed. This covalent molecular compound formed has the formula of HCl.

b. Explain the formation of the above compound.

( 5 + 5 + 3 points )

5. Manufactured substances in industries

a. Draw the arrangement of atoms for the following pure metal and its alloy.

Copper Bronze

6. Acids and Bases

a. The following data shows the differences in pH value for samples of acids having the same

concentration e.g. 0.5 mol/dm3. Explain.

All acids are of 0.5 mol/dm3

concentration

Ethanoic acid Hydrochloric acid Hydrochloric acid Sulphuric acid

pH 6 pH 4 pH 4 pH 2

b. 3 sets of medium are prepared. Set 1: hydrogen chloride gas is dissolved in water. Set 2: hydrogen

chloride gas mixed with methylbenzene. Set 3: hydrogen chloride gas is left dry without any solvent.

Zinc powder is added into each of the medium. Predict your observations and explain why for each

of the sets of experiment.

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7. Electrochemistry

a. Draw a labled diagram for the following set up of apparatus of electrolysis.

Electrolyte

– NaCl (aq)

0.001 moldm-3

Electrodes – Carbon

Electrolyte

– CuSO4 (aq)

Electrodes – Carbon

Electrolyte

– CuSO4 (aq)

Electrodes – Copper

8. Periodic table of elements

a. Explain in terms of electron arrangement why…

Elements of group 18 are chemically inert/unreactive compared to elements of group 17

b. Explain in terms of electron arrangement why

Going down group 1 the elements become more reactive.

c. Explain in terms of electron arrangement why

Going down group 17 the elements become less reactive.

9. Chemical formulae and equations

a. 0.36 g of carbon combines with 0.06 g of hydrogen to form a hydrocarbon. The relative molecular

mass of the hydrocarbon is 42. Calculate: The empirical formula of the hydrocarbon and The

molecular formula of the hydrocarbon. ( Relative atomic mass: C,12; O,16 ).

10. Salts

a. Describe a laboratory activity to prepare a dry and pure crystals of copper(II) sulphate using

copper(II) carbonate solid and sulphuric acid. You are also provided with appropriate apparatus to

carry out the activity. [ 6 + 3 + 1 points ]

b. Describe a laboratory activity to prepare a dry and pure magnesium carbonate using magnesium

nitrate solution and potasium carbonate solution. You are also provided with appropriate apparatus

to carry out the activity. [ 5 + 3 + 1 + 1 points ]

c. Describe a laboratory activity to prepare a dry and pure crystals of zinc carbonate using zinc oxide,

nitric acid and sodium carbonate solution. You are also provided with appropriate apparatus to carry

out the activity. [ 9 points ]

End of Task

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Tips

Definition:

Isotope:

Is atoms of an element

That have same number of proton but different number of neutrons

Acid:

Is a chemical substance

That dissociates in water to produce hydrogen ions

Base:

Is a chemical substance

That reacts with acid to produce salt and water only

Alkali:

Is a soluble base

That dissociates in water to produce hydroxide ions

Weak alkali:

Is an alkali

That produces high concentration of hydroxide ions – dissociates partially in water

Empirical formula:

Is a ……. ( formula )

That ….. ( shows the …. )

DO NOT:

Question:

State one precaution that must be taken before the copper(II)oxide is heated?

Inaccurate answer:

Remove oxygen gas from the combustion tube. [ The word ‘remove’ does not indicate the action verb to

explain what we need to do ]

Accurate answer:

Allow dry hydrogen gas to flow into the combustion tube for a period of time

Question:

State one precaution that must be taken before magnesium strip is heated.

Inaccurate answer:

Remove the oxide layer from the surface of magnesium strip [ The word ‘remove’ does not indicate the

action verb to explain what we need to do ]

Accurate answer:

Rub the surface of magnesium using a piece of sand paper

Basicity of acids and alkalis:

H2SO4 – has higher concentration of H+ ions - diprotic acid – 2 mols of H+ ions/H2SO4 – 2 times

concentration of H+ ions

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COMPARED TO

HCl – has lower concentration of H+ ions - monoprotic acid – 1 mol of H

+ ions/HCl – 1 time concentration

of H+ ions

Question

What is meant by molecular kinetic theory?

Is a …. ( theory )

Which states that …. ( minute and discrete and moves )

Question

Matter exists in three physical states.

Describe briefly how particles are arranged in all the states.

Solid:

Closely packed- Vibrate and circulate at its axis

Liquid:

Move randomly

Intact with each other but not closely packed

Gas:

Particles are further apart to each other

Move at random

Explain the physical properties of molecules at its melting point

a. Substance Q is in both solid and liquid state b. Particles releases heat energy to form bonds during

condensation c. Energy content of particles decreases d. Arrangement of particles closer to each other and is

arranged orderly e. Less movement of particles

Order of increasing atomic radius

( This is the physical properties atoms of elements along a period )

Z<Y<X √1

(All atoms have 3 occupied shells)Z has the most number of protons than Y and Z√2 Z has the

strongest forces of attraction of nucleus and electrons√3

1. Z has the least distant between nucleus and valence electrons√4

Electron arrangement of atom of sodium, Na is 2.8.1

2. Achieve stable electron arrangement

3. Atom of sodium releases one valence electron to atom of chlorine to form ion of sodium, Na+

4. Electorn arrangement of ion of sodium, Na+ is 2.8

5. Ionic equation for the formation of ion of sodium, Na+ is Na e + Na+

Explain the formation of an ionic compound between Na and Cl.

1. Electron arrangement of atom of chlorine, Cl is 2.8.7

2. Achieve stable electron arrangement

3. Atom of chlorine receives one electron from atom of sodium to form ion of chloride, Cl-

4. Electron arrangement of ion of chloride, Cl- is 2.8

5. Ionic equation for the formation of ion of chloride, Cl- is Cl + e Cl

-

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1. Electrostatic force exerted between two opposite ions

2. It forms an ionic bond

3. Molecular formula of the compound is NaCl

( Where necessary the figure showing the electron arrangement of the compound can be drawn carefully )

OR ( eg Formation of ionic compound between X and Z )

1. Atom of X and Z achieve stable electron arrangement√1

2 atom of X release 1 valence electron each to 1 atom of Z√2

X e + X+ // Z + 2e Z

2- √

3

Electrostatic forces exerted between the opposite charges√4

Ionic bond is formed√5

Formula of compound is XZ2 √6

a. Electron arrangement of atom of carbon, C is 2.4

b. Electron arrangement of atom of oxygen, O is 2.6

c. Achieve stable electron arrangement

d. One atom of carbon

e. Share four valence electrons each two electrons

f. With four valence electrons two atom of oxygen each two electrons

g. Four pairs of electrons shared to form four covalent bonds between atom of carbon and oxygen

h. Molecular formula is CO2

25 cm3 0.5 mol dm

-3 copper(II)chloride solution reacts with excess lead(II)nitrate solution to produce

solid lead(II)chloride salt. Calculate the maximum mass of lead(II)chloride produced. [RAM: Pb,207;

Cl,35.5]

1. Mol = 0.5 X 25/1000 = 0.0125 mol

2.(a) Pb(NO3)2 + CuCl2 PbCl2 + Cu(NO3)2

2.(b) 1 mol CuCl2 1 mol PbCl2

3. 0.0125 mol CuCl2 0.0125 mol PbCl2

4. = 0.0125 X [207 +2(35.5)] = 0.0125 X 278 = 3.48 g

Periodic table

1. Explain the changes in sizes of atoms of elements across a period; eg between Na and Cl

- size of atom of Cl is smaller to Na (decreases across the period)

- Cl has more proton to Na (number of proton increases across the period)

- Cl has stronger forces of attraction between nucleus and valence electrons (forces of attraction between

nucleus and valence electrons increases across the period)

- Cl has shorter distance between nucleus and valence electrons compared to Na (distance between nucleus

and valence electrons decreases across the period)

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Explain the changes in the reactivity of elements down the group 1

- reactivity increases down the group

- ease of becoming cations increases

- ease of losing valence electrons increases

- forces of attraction between nucleus and valence electrons decreases

- size of atoms of elements increases

Explain the changes in the reactivity of elements down the group 17

- reactivity decreases down the group

- ease of becoming anions decreases

- ease of gaining electrons decreases

- forces of attraction between nucleus and valence electrons decreases

- size of atoms of elements increases

Explain the changes in melting and boiling point of elements down the group 1

- size of atoms decreases

- metallic bonds between atoms decreases

- energy absorbed to overcome the metallic bonds decreases

- melting and boiling points decreases

Explain the changes in melting and boiling points down the group 17

- melting and boiling points decreases

- size of atoms/molecules decreases

- forces of attraction between molecules (Van de Waals) decreases

- energy absorbed to overcome the forces decreases

Graph of heating and cooling of either naphthalene or acetamide:

Interconversion of molecular compound like napthalene or acetamide:

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a. Melting through heating process

b. Freezing through cooling process

Change this H to Cl to form monomer chloroethene and polymer polyvinyl chloride or CH3 to form

monomer propene and polymer polypropene

Explain why butane(C4H10) and butene(C4H8) have different sootiness:

- butene gives more soot

- calculate (% of C by mass per molecule: Butane=53.33% Butene=66.66%)

- butene has more % of C by mass per molecule

Explain why butanol gives more heat of combustion to ethanol:

- butanol has more C and H atoms

- butanol forms more CO2 and H2O

- more heat is released to the surrounding

Explain the difference in heat change (mcQ) and heat of precipitation (∆H) in the following situation:

a. NaCl + AgNO3 AgCl + NaNO3

b. KCl + AgNO3 AgCl + KNO3

Heat change and heat of precipitation is the same because the same AgCl is produced

Explain the difference in heat change (mcQ) and heat of precipitation (∆H) in the following situation:

(i)NaOH + HCl NaCl + H2O (monoprotic acid) (ii)2NaOH + H2SO4 Na2SO4 + 2H2O (diprotic acid)

Heat change in (ii) is greater because concentration of H+ ions is 2 X more – 1 mol of H2SO4 produce 2 mol

H+ ions – diprotic acid

C C

H H

H H

Polymer

Monomer

n

C C

H H

H H

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Heat of neutralization is the same because it is the amount of heat released to the surrounding when 1 mol of

H+ and 1 mol of OH

- ions react to form 1 mol of H2O

(i)NaOH + HCl NaCl + H2O

(ii)NaOH + CH3COOH NaCH3COO + H2O

Both heat change and heat of neutralization of (i) is greater than (ii) because ethanoic acid is weak acid –

heat released is reabsorbed to dissociate the acid molecule

Explain why using higher concentration of acid gives higher rate of reaction with carbonates?

- rate of reaction is higher BECAUSE

- concentration of acid is higher BECAUSE

- concentration of H+ ions is also higher THUS

- more freq of collision between H+ ions and carbonates THEREFORE

- more freq of EFFECTIVE collision between H+ ions and carbonates

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SOALAN KUIZ KBAT KIMIA

PERIODIC TABLE OF ELEMENTS

1. The atomic numbers of Nitrogen, Oxygen and Fluorine are 7, 8, and 9 respectively. Write the electronic

arrangement of each element and answer the following:

(a) Out of N, O and F which is most electronegative and which one is least electronegative?

(b) What is the number of valence electrons of F?

(c) What is the valency ( charge of ions ) of each of N, O and F?

2. Two elements X and Y have atomic numbers 12 and 16 respectively.

a. Write the electronic configuration for these elements.

b. To which period of the modern periodic table do these two elements belong?

c. What type of bond will be formed between them and why?

3. What family on the periodic table is most associated with each of the following

properties?

a. All are diatomic:

b. Form +2 ions:

c. Unreactive:

d. Highest melting and boiling points:

e. Why do elements in the same family have similar properties?

4. The following diagram shows the set up of apparatus in an experiment to determine the empirical formula of

an oxide of lead.

Which of the following is not correct in the set up of apparatus for this experiment?

I No Bunsen burner

II Fixing of the cork

III Position of the thistle funnel

IV Position of the delivery tube

A I and III only

B II and IV only

C I, II and III only

D I, III and IV only

Zinc Dilute sulphuric acid

Oxide of lead

Combustion tube

Thistle funnel

Delivery tube

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ACIDS AND BASES

1. Hydrogen chloride is a neutral gas and dissolves in water to form a acidic solution.

a. Explain why dry hydrogen chloride gas is neutral

b. Explain why aqueous hydrogen chloride is acidic

c. Describe how sodium carbonate can be used to confirm that an aqueous solution contains an acid

2. A first aid manual suggests that vinegar should be used to treat wasp sting and baking soda for bee stings.

a. What does this information tell you about the chemical nature of the wasp stings

b. If there were no baking soda in the house, what other household substance could you use to treat bee stings?

3. What are the products of the reaction between ethanoic acid and sodium carbonate?

I Water

II Ethyl ethanoate

III Carbon dioxide

IV Sodium ethanoate

A I and III only

B II and IV only

C I, II and III only

D I, III and IV only

4. The following equation represents a neutralization reaction

Acid + base salt + water

Which pairs are reactants in neutralizations reactions?

I sulphuric acid + sodium hydroxide

II hydrochloric acid + solid copper (II) oxide

III sulphuric acid + solid calcium carbonate

IV hydrochloric acid + potassium carbonate solution

A I and II only

B I and IV only

C II and III only

D III and IV only

SALTS

1. A student has mixed the solutions of lead (II) nitrate and potassium iodide.

a. What is the colour of the precipitate formed?

b. Can you name the compound precipitated ?

c. Write the balanced chemical equation for this reaction.

d. What type of reaction is it?

2. Compound P forms enamel of teeth. It is the hardest substance of the body. It does not dissolve in water but it

is corroded when pH in the mouth is below 5.5.

a. How does tooth paste prevent dental decay?

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3. Which of the following ions form a white precipitate that dissolves in excess sodium hydroxide solution?

I Al3+

II Mg2+

III Pb2+

IV Zn2+

A I and II only

B II and IV only

C I, II and III only

D I, III and IV only

4. 3.2 g of copper (II) oxide powder is reacted with excess dilute nitric acid.What is the mass of copper (II)

nitrate formed in the reaction? ( Relative atomic mass of N,14;O,16 and Cu,64 )

A 3.76 g

B 4.96 g

C 5.04 g

D 7.52 g

RATE OF REACTIONS

1. 2.0 g calcium carbonate granules is added to 20.0 cm3 0.1 moldm

-3 hydrochloric acid in a conical flask.

a. Suggest a method to increase the rate of reaction. By using the collision theory, explain how the factor affects

the rate of the reaction

b. Based on the collision the theory, explain why we need to store fresh milk in a refrigerator

2. 2.0 g calcium carbonate granules is added to 20.0 cm3 0.1 moldm

-3 hydrochloric acid in a conical flask.

a. Suggest a method to increase the rate of reaction. By using the collision theory, explain how the factor affects

the rate of the reaction

b. Based on the collision the theory, explain why we need to store fresh milk in a refrigerator

3. An equation of a reaction is as follows :

In the reaction represent by the equation above, it was found that the change of colour from green to brown was

faster when the reactant mixture was heated. This was due to the

I decrease in the activation energy

II increase in the frequency of effective collision

III increase in the kinetic energy of ferrum (II) ions and chlorine molecules.

IV increase in the frequency of collision between ferrum (II) ions and chlorine molecules.

2Fe2+ + Cl2 2Fe3+ + 2Cl- Green Brown

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A I and II only

B II and III only

C I, III and IV only

D II, III and IV only

4. If you want to cook 100 potatoes within a short time, which is the most suitable method ?

A Boil the potatoes in a pan

B Boil the potatoes in a pressure cooker

C Steam the potatoes in a steamer

D Fry the potatoes in a wok

CARBON COMPOUNDS

1. Hydrocarbon `X` and `Y` having molecular formulae C3H8 and C3H6 respectively. Both are burnt in different

spatula on a bunsen flame.

a. Indicate the color of the flame produced by `X` and `Y`.

b. Identify `X` and `Y`.

c. Write the structural formulae.

2. A compound `X` has molecular formula C4H10. It undergoes substitution reaction readily than addition

reaction. It burns with blue flame and is present in LPG.

a. Identify `X` and

b. Give the balanced equation for its combustion and

c. Substitution reaction with Cl2 in presence of sunlight.

3. Which of the following equations can produce fruit flavouring?

I CH3COOH + NaOH CH3COONa + H2O

II C2H5OH + C2H5COOH C2H5COOC2H5 + H2O

III C3H7OH + 2[O] C2H5COOH + H2O

IV C8H17OH + CH3COOH CH3COOC8H17 + H2O

A I and III only

B II and IV only

C III and IV only

D I, II and IV only

4. The following diagram is a molecular formula which represents an organic compound.

What is the name of the organic compound?

A. Eythl ethanoate

B. Eythl methanoate

C. Methyl ethanoate

D. Methyl methanoate

End of Questions

C2H

5 C

O

-

II

O

- H -