This is a "Mock" exam for the Chemistry component of the EDUP1004 Science Foundations Course. It has the same form as the final exam. Some of the questions have 5 possible answers, some 4 and some 3. There are 25 multiple choice questions each worth 1 mark. In the exam you will have a copy of the periodic table. (Which includes the names of the elements)

EDUP1004 Mock Exam (Chemistry)

Your feedback on these self-help problems is appreciated. Click here to send an e-mail to Meredith. To find the annotated answer to the question click on the answer at the right hand edge of the question.

Shortcut to Questions

Q: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Questions 1-3 refer to the following information.

The scenes below, labelled A-E, represent various types of matter on the atomic scale.

   
 

1

Which scene represents a mixture?

     A       B         C         D         E        

Answer 1

2

Which scene represents a gas consisting of diatomic particles?

     A       B         C         D         E        

Answer 2

3

Which scene represents an element that flows to fit the shape of its container but displays a surface?

     A       B         C         D         E        

Answer 3

4

Given that the F-, O2-, Li+ and Mg2+ ions are all approximately the same size, which of the following compounds has the highest melting point?

A:          LiF

B:          Li2O

C:          MgF2

D:          MgO

Answer 4

5

How many protons (p), neutrons (n) and electrons (e) are present in an atom of uranium isotope ?

A:          92p, 235n, 92e

B:          92p, 92n, 238e

C:          238p, 92n, 146e

D:          146p, 92n, 146e

E:          92p, 146n, 92e

Answer 5

6

Which of the following best defines the word allotrope?

A: Different structural forms of an element

B: Elements that possess properties intermediate between those of metals and non-metals

C: Atoms of a given atomic number that have a different number of neutrons

D: Atoms of a given atomic number that have a different number of electrons

D: The different phases (solid, liquid, gas) of a substance

Answer 6

7

How many electrons are there in the valence (or outermost) shell of Cl-?

     A 1      B 7      C 8      D 17      E 18

Answer 7

8

What is the chemical symbol of the element tin?

A:          Am

B:          At

C:          Sb

D:          Sn

E:          Ti

Answer 8

9

The following boxes represent a chemical reaction between elements A (larger, dark grey) and B (smaller, light gray):

   

Which of the following best represents a balanced equation for the reaction?

A:          2A + 2B → A2 + B2

B:          A2 + B2 → 2AB

C:          B2 + 2AB → 2B2 + A2

D:          3A2 + 4B2 → 6AB

E:          2A + 2B → 2AB

Answer 9

Questions 10 and 11 refer to the following information.

Box A represents one unit volume of a solution, A. Boxes B-E represent one unit volume of solutions obtained by diluting solution A by adding extra solvent.

 
     

10

Which box represents the dilution obtained by adding enough solvent to solution A to triple its volume?

     B         C         D         E        

Answer 10

11

Which box represents the dilution obtained by adding enough solvent to solution A to double its volume?

     B         C         D         E        

Answer 11

12

Which of the following processes is endothermic?

A: When concentrated sulfuric acid is added to water, the water gets hot.

B: Natural gas (CH4) is burned on a gas stove.

C: Water is frozen in a freezer.

D: Glucose is metabolised to warm the body.

E: Water is boiled in a kettle.

Answer 12

13

Do the strength of intermolecular forces in a liquid change as the liguid is heated?

A: Yes, the intermolecular forces get stronger.

B: Yes, the intermolecular forces get weaker.

C: No, there is no change in the strength of the intermolecular forces

Answer 13

14

Which of the following statements is TRUE?

A: Water molecules have a net charge.

B: The OH bond in water is polar.

C: One molecule of water dissolves to form two H+ ions and one O2- ion.

D: The OH bond in water is an ionic bond.

Answer 14

15

Which one of the following situations best describes the forces responsible for the formation of a convex meniscus by mercury in a glass thermometer?

A: The intermolecular forces between mercury atoms are stronger than the attractive forces between the mercury and the glass.

B: The intermolecular forces between mercury atoms are weaker than the attractive forces between the mercury and the glass.

C: The intermolecular forces between mercury atoms are exactly equal to the attractive forces between the mercury and the glass.

D: Only intermolecular forces between mercury atoms are important since a thermometer has a small diameter.

Answer 15

16

Plain-carbon steel is a metal alloy, a combination of two elements, iron and carbon. As carbon content rises the metal becomes harder and stronger but less ductile. Which of the following statements best describes why steel with a high carbon content has a much higher tensile strength but is less ductile than iron.

A: There are no flaws in perfect crystals.

B: The grain boundaries between the crystallites prevent dislocations from propagating through iron.

C: The carbon atoms in steel are too far apart to move easily.

D: The carbon atoms prevent the iron atoms, which are arranged in a crystal lattice, from moving over each other.

E: Iron is a liquid and so deforms easily.

Answer 16

17

Which statement best describes why metallic tin crumbles into powder at low temperatures?

A: The low temperature form of tin is more dense and the contraction in volume causes the tin to crumble.

B: The low temperature form of tin is less dense and the expansion in volume causes the tin to crumble.

C: The tin crystals are very brittle.

D: Impurities in the tin weaken its structure.

E: The tin atoms in the crystal lattice move easily over each other.

Answer 17

18

In molecules carbon and nitrogen can form single bonds (C-N), double bonds (C=N) and triple bonds (C N). Which one of the following statements is FALSE?

A: Two electrons are shared in a carbon/nitrogen double bond (C=N).

B: Single bonds are longer than double bonds.

C: Triple bonds are stronger than double bonds.

D: Multiple bonds form so that each carbon and nitrogen atom has 8 electrons.

E: It is harder to decompose molecules with double bonds compared to molecules with only single bonds.

Answer 18

19

Which one of the following statements is TRUE?

A: Water will rise higher in a less narrow capillary tube.

B: The addition of a detergent lowers the surface tension of water.

C: Surfactants have a head group that interacts strongly with water and a tail group that can interact strongly with grease.

D: Soap bubbles last longer on a sunny day than on a rainy day.

E: The force between water molecules in a liquid is an adhesive force.

Answer 19

20

Which of the following statements is true?

A:      In a micelle the hydrophobic tail of a surfactant molecule points outwards, toward water molecules.

B:      Bubbles will last longer on a hot sunny day than on a cold wet day

C:      Bubbles are spherical because the sphere is the shape that has the largest possible surface area for a given volume.

D:      When detergent is added to milk, it will help the fat in the milk to form micelles.

E:      Water will rise higher in a wide glass tube than in a narrow glass tube.

Answer 20

21

The following diagram represents energy versus reaction progress for a chemical reaction.

Which one of the following statements is TRUE?

A: The forward reaction is endothermic.

B: The activation energy for the forward reaction is larger than the activation energy for the reverse reaction.

C: The overall energy change for the forward reaction is +20 kJ mol-1.

D: The overall energy change for the forward reaction is -20 kJ mol-1.

E: The activation energy for the forward reaction is +70 kJ mol-1.

Answer 21

22

The following schematic diagrams describe the reaction of chlorine gas, Cl2 (g), with metallic sodium, Na (s), to form sodium chloride, NaCl (s) in a sealed test tube.

   

Which one of the following statements is FALSE?

A: The reaction can be described by the equation 2Na + Cl2 → 2NaCl.

B: The quantity of chlorine introduced was insufficient to react with all the sodium.

C: The quantity of sodium introduced was insufficient to react with all the chlorine.

D: Sodium chloride, NaCl, is an ionic solid.

E: Sodium ions, Na+ are smaller than sodium atoms, Na.

Answer 22

Questions 23 and 24 refer to the following information.

The scenes below, labelled A-E, represent various types of solid materials.

   
 

23

Which scene represents a defect called a "slip dislocation"?

     A       B         C         D         E        

Answer 23

24

Which scene represents an alloy?

     A       B         C         D         E        

Answer 24

25

Which of the following statements is FALSE?

A: Water can act as both an acid and a base.

B: Acids often have a sharp, sour taste.

C: Soda water is an acidic solution.

D: Bases often have a slippery feel because of their caustic effects on the fats in skin.

E: Acids are substances that dissolve to produce OH- ions.

Answer 25

 











Answers

1

Which scene represents a mixture?

     A       B         C         D         E        

Question 1

2

Which scene represents a gas consisting of diatomic particles?

     A       B         C         D         E        

Question 2

3

Which scene represents an element that flows to fit the shape of its container but displays a surface?

     A       B         C         D         E        

Question 3

4

Given that the F-, O2-, Li+ and Mg2+ ions are all approximately the same size, which of the following compounds has the highest melting point?

A:          LiF

B:          Li2O

C:          MgF2

D:          MgO


Melting point is a measure of the size of the attractive interactions between the particles. The greater the attraction the higher the melting point. The interaction between unlike charges depends on how far the charges are away from each other and how big the charges are. The ions are all about the same size so the distance is the same in all 4 cases. The charges are highest for MgO (+2 and –2) so therefore it has the strongest interactions and the highest melting point.

Question 4

5

How many protons (p), neutrons (n) and electrons (e) are present in an atom of uranium isotope ?

A:          92p, 235n, 92e

B:          92p, 92n, 238e

C:          238p, 92n, 146e

D:          146p, 92n, 146e

E:          92p, 146n, 92e


The neutral Uranium atom has 92 protons, 92 electrons and a mass of 238. It therefore has 238 – 92 = 146 neutrons.

Question 5

6

Which of the following best defines the word allotrope?

A: Different structural forms of an element

B: Elements that possess properties intermediate between those of metals and non-metals

C: Atoms of a given atomic number that have a different number of neutrons

D: Atoms of a given atomic number that have a different number of electrons

D: The different phases (solid, liquid, gas) of a substance


Metalloids are elements that possess properties intermediate between those of metals and non-metals.
Isotopes are atoms of a given atomic number that have a different number of neutrons.
Ions are atoms of a given atomic number that have a different number of electrons.
Phases are the solid, liquid and gas forms of a substance.

Question 6

7

How many electrons are there in the valence (or outermost) shell of Cl-?

     A 1      B 7      C 8      D 17      E 18


Neutral chlorine has 17 protons and 17 electrons, 7 of which are in its outermost shell. The chloride ion, Cl-, has one extra electron so has 8 electrons in its outermost shell.

Question 7

8

What is the chemical symbol of the element tin?

A:          Am

B:          At

C:          Sb

D:          Sn

E:          Ti


Am is Americium, element 95; At is Astatine, element 33, Sb is Antimony, element 51, and Ti is Titanium, element 22.

Question 8

9

The following boxes represent a chemical reaction between elements A (larger, dark grey) and B (smaller, light gray):

   

Which of the following best represents a balanced equation for the reaction?

A:          2A + 2B → A2 + B2

B:          A2 + B2 → 2AB

C:          B2 + 2AB → 2B2 + A2

D:          3A2 + 4B2 → 6AB

E:          2A + 2B → 2AB


The two reacting species are both diatomics, ie A2 and B2, they form the compound AB and balancing the reaction A2 + B2 → 2AB

Question 9

10

Which box represents the dilution obtained by adding enough solvent to solution A to triple its volume?

     B         C         D         E        


3 times the volume gives 1/3 the number of solute particles per unit volume and 12/3=4.

Question 10

11

Which box represents the dilution obtained by adding enough solvent to solution A to double its volume?

     B         B         C         D         E        


2 times the volume gives 1/2 the number of solute particles per unit volume and 12/2=6.

Question 11

12

Which of the following processes is endothermic?

A: When concentrated sulfuric acid is added to water, the water gets hot.

B: Natural gas (CH4) is burned on a gas stove.

C: Water is frozen in a freezer.

D: Glucose is metabolised to warm the body.

E: Water is boiled in a kettle.


Endothermic means that the overall process draws heat from the surroundings (needs heat to proceed).
When concentrated sulfuric acid is added to water, the water gets hot because heat is released to the surroundings, ie it is exothermic.
Although when natural gas (CH4) is burned on a gas stove it requires a match or a spark to start (to get over the activation energy barrier) the overall process releases heat, which is why you can use it to cook other things, so it is exothermic.
When water is frozen it forms a hydrogen bonded network and forming these bonds releases energy, which is why farmers spray water mists on fruit trees to warm the fruit up in a frost, so this is, again, an exothermic process.
Glucose is effectively burned by the body as fuel: the energy released drives other metabolic processes like moving muscles, so again it is exothermic.
To boil water we need to heat it to break the intermolecular bonds between water molecules (hydrogen bonds) that exist in liquid water. Because we need to put heat into the reaction, boiling water is endothermic.

Question 12

13

Do the strength of intermolecular forces in a liquid change as the liguid is heated?

A: Yes, the intermolecular forces get stronger.

B: Yes, the intermolecular forces get weaker.

C: No, there is no change in the strength of the intermolecular forces


The water molecules move faster and get further apart as the temperature rises. The strength of the intermolecular forces depend on how far apart the molecules are so they get weaker as the liquid is heated.

Question 13

14

Which of the following statements is TRUE?

A: Water molecules have a net charge.

B: The OH bond in water is polar.

C: One molecule of water dissolves to form two H+ ions and one O2- ion.

D: The OH bond in water is an ionic bond.


Water molecules are neutral, however the OH bond is polar: the H atom has a slight +ve charge and the O atom has a slight ve charge. When water dissolves (in water!) the bonds inside the water molecule are not broken, however the polar nature of the OH bond allows hydrogen bonds to form in the liquid (not ionic bonds).

Question 14

15

Which one of the following situations best describes the forces responsible for the formation of a convex meniscus by mercury in a glass thermometer?

A: The intermolecular forces between mercury atoms are stronger than the attractive forces between the mercury and the glass.

B: The intermolecular forces between mercury atoms are weaker than the attractive forces between the mercury and the glass.

C: The intermolecular forces between mercury atoms are exactly equal to the attractive forces between the mercury and the glass.

D: Only intermolecular forces between mercury atoms are important since a thermometer has a small diameter.


Hopefully self-explanatory!

Question 15

16

Plain-carbon steel is a metal alloy, a combination of two elements, iron and carbon. As carbon content rises the metal becomes harder and stronger but less ductile. Which of the following statements best describes why steel with a high carbon content has a much higher tensile strength but is less ductile than iron.

A: There are no flaws in perfect crystals.

B: The grain boundaries between the crystallites prevent dislocations from propagating through iron.

C: The carbon atoms in steel are too far apart to move easily.

D: The carbon atoms prevent the iron atoms, which are arranged in a crystal lattice, from moving over each other.

E: Iron is a liquid and so deforms easily.


The additives in alloys disrupt the natural crystal structure of the metal preventing the metal atoms from sliding too far over each other, that is, the ductility of the metal is reduced. This is what gives steel its strength.

Question 16

17

Which statement best describes why metallic tin crumbles into powder at low temperatures?

A: The low temperature form of tin is more dense and the contraction in volume causes the tin to crumble.

B: The low temperature form of tin is less dense and the expansion in volume causes the tin to crumble.

C: The tin crystals are very brittle.

D: Impurities in the tin weaken its structure.

E: The tin atoms in the crystal lattice move easily over each other.


As the temperature decreases the structure of the tin changes from a dense tetragonal, metallic structure (beta-tin) to a much less dense, diamond-like structure that behaves like a semi-conductor (alpha-tin). The increase in volume as the tin changes from the more dense form to the less dense form typically causes tin objects to crumble.

Question 17

18

In molecules carbon and nitrogen can form single bonds (C-N), double bonds (C=N) and triple bonds (C N). Which one of the following statements is FALSE?

A: Two electrons are shared in a carbon/nitrogen double bond (C=N).

B: Single bonds are longer than double bonds.

C: Triple bonds are stronger than double bonds.

D: Multiple bonds form so that each carbon and nitrogen atom has 8 electrons.

E: It is harder to decompose molecules with double bonds compared to molecules with only single bonds.


A chemical bond is 2 shared electrons, a double bond (2 bonds) therefore involves 4 shared electrons. Because more electrons are shared, double bonds are shorter and stronger (ie harder to break) than single bonds (the atoms are closer together) and triple bonds are shorter and stronger than double bonds. Multiple bonds form so each atom can complete its octet of outer electrons.

Question 18

19

Which one of the following statements is TRUE?

A: Water will rise higher in a less narrow capillary tube.

B: The addition of a detergent lowers the surface tension of water.

C: Surfactants have a head group that interacts strongly with water and a tail group that can interact strongly with grease.

D: Soap bubbles last longer on a sunny day than on a rainy day.

E: The force between water molecules in a liquid is an adhesive force.


Capillary action results from the very high adhesive forces between water and glass. Water will rise in a thin tube (a capillary) until the adhesive force is exactly balanced by the force of gravity pulling the water downwards. In a narrow tube there is a smaller weight of water so the water can rise higher.
Adding a surfactant changes the nature of the water surface: the surfactant molecules line up on the surface and the forces between them are less than the forces between water molecules so the surface tension is lowered.
C is a description of what a surfactant is: the head groups are often charged so they have very strong interactions with water whilst the tails very much resemble grease molecules so using like-dissolves-like the tails can dissolve grease.
Soap bubbles last longer on a rainy day because the high humidity in the air slows down the evaporation of water from the soap film.
The forces between liquid molecules are called cohesive forces, the forces between the liquid molecules and anything else are called adhesive forces.

Question 19

20

Which of the following statements is true?

A:      In a micelle the hydrophobic tail of a surfactant molecule points outwards, toward water molecules.

B:      Bubbles will last longer on a hot sunny day than on a cold wet day

C:      Bubbles are spherical because the sphere is the shape that has the largest possible surface area for a given volume.

D:      When detergent is added to milk, it will help the fat in the milk to form micelles.

E:      Water will rise higher in a wide glass tube than in a narrow glass tube.

Question 20

21

The following diagram represents energy versus reaction progress for a chemical reaction.

Which one of the following statements is TRUE?

A: The forward reaction is endothermic.

B: The activation energy for the forward reaction is larger than the activation energy for the reverse reaction.

C: The overall energy change for the forward reaction is +20 kJ mol-1.

D: The overall energy change for the forward reaction is -20 kJ mol-1.

E: The activation energy for the forward reaction is +70 kJ mol-1.


The reactants are at higher energy than the products so the overall reaction releases energy and is exothermic. For an exothermic reaction we have a negative energy change (energy exits) and this is -20 kJ mol-1.
The barrier (or activation energy) for the forward reaction is +50 kJ mol-1 and is lower than the barrier to the reverse reaction, +70 kJ mol-1.

Question 21

22

The following schematic diagrams describe the reaction of chlorine gas, Cl2 (g), with metallic sodium, Na (s), to form sodium chloride, NaCl (s) in a sealed test tube.

   

Which one of the following statements is FALSE?

A: The reaction can be described by the equation 2Na + Cl2 → 2NaCl.

B: The quantity of chlorine introduced was insufficient to react with all the sodium.

C: The quantity of sodium introduced was insufficient to react with all the chlorine.

D: Sodium chloride, NaCl, is an ionic solid.

E: Sodium ions, Na+ are smaller than sodium atoms, Na.


Sodium chloride is a 1:1 ratio of sodium and chlorine ions, written as NaCl. The reaction, as written, is balanced.
Because the solid is made up of Na+ and Cl- ions it is an ionic solid.
Positive ions are smaller than neutral atoms because the positively charged nucleus pulls the remaining electrons closer to it, ie the electrons feel a larger effective charge.
In the reaction, at completion (artistic license here), there are remaining sodium atoms, thus, the quantity of chlorine introduced was insufficient to react with all the sodium. The FALSE statement is therefore: The quantity of sodium was insufficient to interact with the all the chlorine.

Question 22

23

Which scene represents a defect called a "slip dislocation"?

     A       B         C         D         E        


A is a representation of a perfect (ideal) crystal; B is a representation of a polycrystalline material; C is a representation of an alloy; D is a representation of a slip dislocation, and E is a representation of a glass.

Question 23

24

Which scene represents an alloy?

     A       B         C         D         E        


A is a representation of a perfect (ideal) crystal; B is a representation of a polycrystalline material; C is a representation of an alloy; D is a representation of a slip dislocation, and E is a representation of a glass.

Question 24

25

Which of the following statements is FALSE?

A: Water can act as both an acid and a base.

B: Acids often have a sharp, sour taste.

C: Soda water is an acidic solution.

D: Bases often have a slippery feel because of their caustic effects on the fats in skin.

E: Acids are substances that dissolve to produce OH- ions.


Water can auto-ionize with other water molecules to produce H3O+ and OH-. Acids produce H+ in solution and bases produce OH- in solution so water can act as both an acid and a base, it is an amphoteric substance.
Acids typically taste sour (eg lemon juice) and bases have a slippery feel to them because of the caustic reaction with the fats in your skin (you should wear rubber gloves when you use bases like oven cleaner).
Soda water contains dissolved carbon dioxide. As the carbon dioxide dissolves in the water it produces carbonic acid (remember breathing into the flasks in the lecture) so soda water (and indeed all water left open to the atmosphere) is acidic.

Question 25

RETURN TO TOP