Chemistry national exam 2013 – SMART ETHIO E-Learning

Welcome to your Chemistry national exam 2013

choose the best answer from the given alternatives

1.

The branch of chemistry that is involved in separation, identifying and determining the relative amounts of components in a sample of material is known as

Analytical chemistry.

Physical chemistry.

Inorganic chemistry.

Biochemistry

2.

Significant figures are figures with

measured values with the highest uncertainty.

measured values with the highest accuracy.

measured values with the highest precision.

exactly known digits with the last digit uncertain.

3.

For the determination of the density of a new ceramic, a student measured the mass of a piece on an analytical and obtained 3.8056 gram and its volume 2.5 mL by displacement of water in a graduated cylinder. The correct reported density of the ceramic should be

3.5 g/mL

1.5224 g/mL

1.5222 g/mL

1.5 g/mL

4.

The scientific method is

a collection of scientific guesses and hypotheses by seeking patterns in the observation.

the sum total of unique guidelines for the practice of science in the world.

a method of arriving at an organized body of knowledge based on reproducible experiments and observation.

the result of fortunate, accidental discovery in the development of science.

5.

One of the following is NOT a cause of uncertainty in measurement?

The environment where the measurement is made

The person doing the experiment

The type of material measured

The measuring device

6.

Which of the fo8owlng is true about isotopes? Isotopes of an element have

the same atomic mass but different atomic numbers.

different physical and chemical properties.

different number of neutrons and the same number protons.

the same number of electrons and neutrons.

7.

The following diagrammatic representations shows the shape for various orbitals. Which one represents the d2/z orbitals?

8.

Sliver (fi = 47) has several known isotopes, but two occur naturally, 107 Ag and 109 Ag. Given the following mass spectrometric data, calculate the atomic mass of Ag

107.94amu

107.4amu

108.9amu

107.86amu

9.

Which statement correctly describes Heisenberg's uncertainty principle?

If we measure the momentum of a particle precisely then its position will be correspondingly precise.

A small particle like the electron can behave both as a particle and a wave.

Both the location and the momentum of a subatomic particle like the electron cannot be precisely known

A particle with a mass moving at a given speed can he described by the wave characteristics of material particles.

10.

Which of the following statement is correct about energy changes when an electron changes its energy level?

When an electron falls from a higher energy level to a lower energy level, the energy is higher than the difference between the two energy levels is emitted.

When an electron jumps from a lower energy level to a higher level, the photon emitted is equal to the difference between the two energy levels.

When an electron jumps from a lower energy to a higher energy level, the energy is equal to the difference between the two energy levels is absorbed.

When an electron falls from a higher energy level to a lower energy level, the energy is equal to the difference between the two energy levels is observed.

11.

The sanitizer in wide use for protection against Covid-19 is labeled 83% alcohol. How can one scientifically check the concentration? This can be done by

making observation.

collection of data.

forming a hypothesis.

experimentation.

12.

The correct electronic configuration for chromium (Cr, Z= 24) is

13.

According to Hund's rule equal energy (degenerate) orbitals are filled with

maximum number of unpaired electrons with parallel spins.

maximum number of unpaired electrons with opposite spins.

two electrons of parallel spins placed in the first orbital.

two electrons of opposite spins placed in the first orbitals.

14.

In the modern periodic table

transition and inner transition elements are placed in the middle of the periodic table.

metals are placed on the right hand side of the periodic table.

elements with similar properties are placed in the same period.

non-metals are placed on the right hand side of the periodic table.

15.

The electrolysis of liquid (molten) NaCl in the set-up for the electrochemical cell is given in the following figure below

which of the following statement is true about the electrolysis of molten sodium chloride?

CI2 is formed at the cathode.

Na is oxidized at the anode.

The net reaction produces Cl 2 at the anode and Na at the cathode.

0 2 is produced at the anode due to oxidation of water.

16.

Covalent compounds are liquids or gases at room temperature and have low melting and boiling points. Which of the fo8owing statements explains these properties of covalent compounds?

Covalent compounds exist as separate molecules.

The unit of particles in covalent compounds are ions.

The intermolecular forces of attraction in covalent compounds are strong.

There are no forces of attraction between the molecules in covalent compounds.

17.

Both carbonyl sulphide , COS(SCO), S= C=O and carbon dioxide (CO2)O=C= O are linear molecules. COS is polar whereas CO 2 is non-polar. this is because

Sulphur is more electronegative than oxygen.

CO 2 has a net dipole moment of zero.

regions of high negative charge is distributed equally around the central atom is COS.

the C=O bonds in both COS and GO2 are polar.

18.

Which of the following statements is true about the formation of CH4 according to valence bond theory?

Carbon can form two hybrid orbitals as it has got only two half-filled orbitals.

The 2s and one 2p orbitals in carbon hybridize to form two SP orbitals.

The 2 s and two 2p orbitals in carbon hybridize to form three Sp3

The 2 and three 2p orbitals in carbon hybridize to form four sp3

19.

Phosphorus ( Z = 15 ) has the electronic configuration 1s22s2 2p63s23p3 , what kind of hybridization does phosphorus undergo in the formation of phosphorus pentachloride(PCI5)

sp3 d

sp

Sp3

sp 2

20.

One of the following reactions illustrates the formation of coordinate covalent bond?

NaOH +HCI-- NaCl+ H2O

Be+2 F2 --BeF 2

CaCO3 +HCl –CaCl2 + H2O+CO2

NH 3 +HCl ---NH+4 + CI-

21.

Hydrogen bonding occurs in compounds that contain H—N, H— O and H-F bonds. These bonds are stronger than the ordinary dipole-dipole interaction because

the partially positive H of one molecule is attracted to the partially negative lone pairs on the N, O or F another molecule.

the H—N, H— O and H—F bonds are non-polar and thus do not interact with neighboring molecules.

the H— N, H— O and H—F bonds are less polar than ordinary covalent bonds.

the small sizes of N , O and makes these atoms so electropositive that their covalently bonded H is highly negative.

22.

Which of the following is an example of exception to the octet rule?

H2 O

NH 3

PCI5

CCI4

23.

Which of the following pair is true about the general properties of the different types of crystalline solids

Type of solid & Hardness & Melting point &

Conduction of heat of electricity

I and IV

I and II

I and III

II and III

24.

.

the basic different structures of each hydride

the small size of O Compared to the other group VIA elements. compared

increasing boiling points with increasing molecular mass.

hydrogen bonding present in H2O molecules.

25.

Given the following catalyzed reactions

Which reactions is examples for homogeneous catalysis?

IV

II and III

I and II

II

26.

Which statement is true about catalyst?

A catalyst slows down or speeds up a reaction, itself being consumed.

A positive catalyst decreases the rate of a reaction by increasing the activation energy.

A negative catalyst increases the rate of a reaction by decreasing the value of activation energy.

The role of a catalyst is to increase or decrease the rate of a reaction by lowering or increasing the activation energy.

27.

According to the transition state theory

the activation energy is the energy that must be absorbed or released by reactants to reach the activated complex.

the standard reaction enthalpy (AH 0) D depends on the magnitude of the activation energy (Ea).

the collision between two reacting species results m the formation of an activated complex, which has less energy than both reactants and products.

in the activated complex, the original bonds are weakened and the new bonds are partially formed.

28.

Which of the following is true about the rate constant?

It expresses the relationship between the rate of a chemical reaction and the volume of reacting species.

The value of a rate constant is independent of reaction conditions.

A small rate constant indicates a faster reaction and a larger rate constant indicates a slower reaction.

The volume of a rate constant tells us how fast or slow a reaction is.

29.

For a first order reaction, the concentration versus time of the reaction mixture is given by the following graph

If a is the initial concentration of the reactant and if the half-life is l hr, after how many hours would be the concentration of reactant reduced to a/32

3 hr

5 hr

4 hr

1hr

30.

The mathematical expression

Arrhenius equation is of important as it

shows

for a given value of activation energy of the rate constant increases as the temperature Increases.

for a given value of activation energy, the value of the rate constant decreases as the temperature increases.

reactions with layer activation energies, the value of the rate constant decreases as the temperature increases.

reactions with larger activation energies have higher values of k and are therefore faster.

31.

From the magnitude of the contribution constant, Keq One can deduce that

Small K eq Values indicate the reaction yields very high amounts of products near equilibrium.

Keq Will be larger when we have higher amounts or reactants over products.

large Keq Value indicates that the reaction B reaches equilibrium with little reactants rerlaining.

intermediate Keq Value indicates that the reaction does proceed in the forward direction.

32.

The statement "If a system at equilibrium is subjected to a stress, the system will readjust itself to reduce the effects of the stress is known as

Avogadro's principle

Le-Chatterley’s principle

Faradays law

Boyle's law

33.

The law of mass action states that

the rate of a reaction is directly proportional to the product of the concentration of reactants raised to the power of their respective coefficients in the balanced equation.

a chemical equilibrium is attained only when the reaction is started with reactants.

the Keq expression is the ratio of the concentrations reactants to the products raised to their coefficients.

for a reaction at equilibrium, the reaction quotient, Q is always less than the equilibrium constant, Keq

34.

for the reaction between gaseous NO and O₂ to form NO₂ (g), what will be the equilibrium constant

35.

The equilibrium constant Kp for the reaction 2SO₃( g)----- 2SO₂ +O₂ (g) is 8 X 10^-3 Kp at 227° C.

What is the value of Kc for the reaction at

the same temperature?

36.

In the production of NH₃ by the Haber

process according to the equation

N₂ ( g)+3H₂ ( g) 2NH₃ (g) H=-92KJmo1^- 3

What are the favorable conditions for the

production of high yield of NH₃ ?

High pressure and low temperature

High pressure and high temperature

Low pressure and low temperature

Low pressure and high temperature

37.

Which one of the following statements describes laboratory and industrial preparation of acetic acid respectively?

The oxidation of ethanol by sodium dichromate and fermentation of ethanol.

Reduction of ethanol by NaBH4 and fermentation of propanol.

Reduction of toluene by KMnO4 and reduction of ethanol by sodium dichromate.

Oxidation of toluene by KMnO4 and fermentation of ethanol.

38.

Which of the following is true about carboxylic acids?

Carboxylic acid with the formula RCOOH.

Methanoic, Ethanoic and Citric acids are monocarboxylic acids.

Propane dioic acid is the simplest dicarboxylic acid.

Citric acid is typical dicarboxylic acid.

39.

What is the IUPAC name for the branched carboxylic acid

CH₃ — CH(C1) —CH(CH₃) —CH(CH₃) — COOH

D 4 - choroal - 1-methyl 1- pentatonic acid.

4- choral -2,3-dimethyl 1- pentatonic acid.

4 choroal -2, methyl 1- pentatonic acid.

1,2-dimethyl 4 - choral 1-pentatonic acid.

40.

Esters are characterized by the following properties EXCEPT

esters have pleasant odors of perfumes and food flavoring.

all esters are soluble in inorganic solvents and organic.

esters have higher boiling point than carboxylic acid and alcohols.

esters have lower boiling point compared to the carboxylic acid and alcohols.

41.

Oils are unsaturated fatty acids. The process of converting oils to solid fats involves?

esterification of the acids.

hydrogenation of C—C double bonds.

halogenations of the C—C double bonds.

saponification with NaOH

42.

A chemistry teacher has added different reactants and reagents in three different test tubes as described below

I. Into the test tube A he added ethanol,
sodium dichromate, sulphuric acid
II. Into the test tube B he added
acetaldehyde, sodium borohydride and water.
III. Into the tube C he added methyl acetate
and ethanol and sodium hydroxide.
In which test tube would a reaction takes place that provide acetic acid?

II and III

I

III

I and II

43.

The difference between colloids and suspension is that

colloidal particles are small enough and do not settle down unlike in a suspension

colloids are as transparent as solution.

both colloids and suspensions are heterogeneous mixtures.

most colloids and suspensions appear cloudy.

44.

The solubility of a substance is the amount of a substance that

dissolves more amount of solute than it can normally dissolve.

gives an unsaturated solution of the substance at given temperature.

dissolves double the amount of solute than it can normally dissolve.

gives a saturated solution of the substance at a given temperature.

45.

187 g/100 g of water Solution

37.4 g/100 g of water

113. 7 g/ 100 g of water

18. 7 g/100 g of water

46.

The "like dissolves like” rule accounts for one of the following observation

The insolubility of I2 in H2 O

The solubility of KBr in C7 H3

The solubility of C2 H 6 IR H2O

The solubility of C6H6in CCII

47.

Which of the following concentration units is correctly defined?

48.

The concentrated sulphuric acid H₂ SO₄ we use in the laboratory is 98% H₂SO₄ t by mass and has a density of 83 g/mL . Below are given the concentration of the acid in Varlous

units. Which of the given alternatives

correctly describes the concentration of the

acid?

18. 3M 3.66 N 0.9

1.83M 3.66 N 0.9

36.6M 18.3N 0.1

18.3M 36. 6 N 0.9

49.

How do you prepare 500 mL of 1 NCa(OH )2 solution?

Ca=40, H=1 , O =16

By dissolving 37 g of Ca(OH)2 in 500 mL of solution.

By dissolving 74 g of Ca(OH)2 in 500 mL of solution.

By dissolving 74 g of Ca(OH)2 in liter of solution.

By dissolving 37 g of Ca (OH )2 in 1 liter solution.

50.

The Ka of acetic CH₃ COOH is 8 x 10^-5 “

What is the percent ionization of

1MCH₃ COOH ?

3.6

1.34

1.42

4.2

51.

According to the Lewis definition of an acid, an acid is a substance that

donates an OH- ion.

accept a H+ ion.

dissociate in water to yield H3O+

accepts a pair of electrons.

52.

Water is a weak electrolyte, because

it has a very high ionic product, Kw.

it acts both as Bronsted- Lowry acid and base.

it undergoes a reversible dissociation with a very low ionic product, Kw.

it can accept a proton from an acid and donate a proton to a base.

53.

Which of the following reactions represent the amphiprotic behavior of water

54.

For an acidic solution, which of the following is correct?

55.

What is the pH of 0.254M HF solution at 25 C The ionization of the weak acid, HF is given by

12.1

12.3

1.89

1.741

56.

One of the following given pairs represents examples of buffer systems

57.

The reaction between a weak acid and strong base is presented by the reaction between acetic acid and NaOH gives a basic solution because

58.

An acid is a substance that

donates a proton in a chemical reaction.

produces more OH +ions in water than H- ions.

donates a pair of electrons to a chemical species.

has a bitter taste.

59.

One of the following given masses of acids constitutions the corresponding equivalent of the acid

60.

One of the following pairs shows Bronsted- Lowry acids behavior in water?

61.

In the reaction mixture of the two NH4 OH and NH4 Cl

62.

Which one of the following is correct about K w at different temperature? The ionic product of water Kw equals

Hydrogen ion concentration at 25° C is higher than at 40° C

40° C pure water is no more neutral.

Hydroxyl ion concentration is higher at 40° C than hydrogen ion concentration.

Water is dissociate to a higher extent at 40° C than at

63.

What is reduction? Reduction is

gain of electrons and no change in oxidation number.

loss of electrons and decrease in oxidation number.

gain of electrons and decease in oxidation number.

gain of electrons and increase in oxidation number.

64.

During the electrolysis of dilute aqueous sulphuric acid, the ions present in solution

are H⁺ , OH⁺ and SO₄^2- . Which ions are

preferentially discharged at the cathode and

anode, respectively?

65.

Which one of the following is NOT correct about electrodes and electrochemical cells?

The overall cell potential is calculated by the formula E ,cell =E calhode - E anode

E ,cell is greater than zero for non-spontaneous process.

The difference in the electrical potential of the electrode is positive that is positive cell.

Electrons flow spontaneously from negative to positive electrode.

66.

The mathematical expressions for Faraday's first law is summarized as

67.

In the electrolysis of copper sulphate solution using graphite electrodes, O₂ is liberated at the anode and copper metal is deposited at the cathode. If the electrolysis of CuSO₄ is performed using copper electrode, what happens at the anode and cathode?

At the anode copper is reduced, where copper is oxidized at the cathode.

No electrochemical reaction takes place involving copper.

At the anode H2 is liberated, whereas copper is deposited at the cathode.

At the anode the copper electrode dissolves and copper metal is deposited at the cathode.

68.

The statement "the amount of a substance consumed or produced in an electrolytic cell is directly proportional to the amount of electricity that passes through the cell' is known as

Henry's law.

Dalton's law.

Raoul's

Faraday’s law.

69.

Given the following electromotive series of selected metals with their standard reduction potentials

Which of the following statements is correct about reactivity of the metals?

Cu is the strongest reducing agent in the group.

Pb is more easily oxidized than Al.

The reaction C u + Zn2 +-- Cu 2 ++Zn is spontaneous.

K is the strongest reduction agent among the metal silver

70.

One of the following is NOT true about the effects of corrosion?

It causes enormous damage to buildings, bridges, ships and cars.

It causes deterioration of metals by spontaneous chemical process.

Damage from corrosion costs billions of dollars annually.

Corrosion forms protection oxide layers to prevent damage.

71.

in the Galvanic cell given in the diagram below

Identify the component parts correctly labelled for the letters a, b, c, d and choose the correct one among the following

a copper cathode b zinc anode c CuSO4 (sol) d voltmeter salt bridge salt bridge voltmeter

Copper Anode b Zinc cathode c voltmeter d salt bridge

Zinc anode b copper cathode d znSo4(sol) d salt bridge

a Zinc Anode b copper cathode c salt bridge d voltmeter

72.

The conversion of nitrogen gas into useful nitrogen compounds is known as

Photosynthesis.

Fixation.

Respiration.

Oxidation.

73.

CO 2 is released into the atmosphere by one of the following processes

Natural fires and volcanoes release CO2 into the air.

Plants consume atmospheric carbon dioxide during photosynthesis.

Utilization of electrical energy as energy sources.

Animals eat pants and release CO 2 by photosynthesis.

74.

One of the following is NOT a common application of silicon

in the control of the frequency of television transmissions.

in coating iron to prevent in from rusting.

in he construction of transistors and microprocessors.

in the production of polish body parts cars.

75.

One of the following is NOT among the chemical properties of silicon

76.

Which one of the following is a common reaction of tin?

77.

The monomer of natural rubber is

78.

All of the following are examples of addition polymers EXCEPT

79.

One of the following examples of polymers is correctly matched with is uses.

Polyethylene; food containers

Polyvinyl chloride; making pipes

Polypropylene; electrical insulation

Polytetrafluoroethylene; making shoes

80.

Natural polymers are

polymers found in some substances reaction of monomer units.

polymers produced by the addition chemistry

polymers produced by the substation rime rubber in nature. the monomer units

polymers produced by condensation reaction of monomer units.

Please Share This Share this content

Leave a Reply Cancel reply

Share this content