Year 11 Chemistry Exam Questions Part 1: Chemical Earth
Posted on May 4, 2017 by DJ Kim
Year 11 Chemistry Exam Questions: Chemical Earth
Assess your depth of knowledge and understanding for the Year 11 Chemistry module ‘Chemical Earth’. Work through these Chemical Earth exam questions below.
You can refer to the Glossary of Key Words for the meaning of any verbs in the questions.
Detailed answers are provided at the bottom of this blog post
Complete the following table.
Draw the electron shell diagram and Lewis dot diagram for oxygen.
What is an isotope?
Give the number of protons, neutrons and electrons of the following isotopes.
Explain why calcium forms cations whereas fluorine forms anions.
Describe the trends in the atomic radii and electronegativity in the periodic table.
What are the physical properties of metals, non-metals and semi-metals?
What is the difference between an element and a compound?
What is the difference between homogenous and heterogenous mixtures? Provide an example for each type of mixture.
How can a pure substance and a mixture be distinguished?
Outline the features of a chemical change and a physical change?
With the aid of a simple diagram, describe the structure of a metal.
Compare the difference between an ionic bond and a covalent bond.
What are the formulae and charges of the following polyatomic ions?
With reference to the structure of ionic compounds, explain why ionic solids are poor conductors of electricity when solid but can conduct electricity when molten or dissolved in water.
Explain the difference in physical properties between diamond (covalent network substance) and carbon tetrachloride (covalent molecular substance).
Name or give the formula for the following compounds:
i) Magnesium chloride
ii) Sodium sulfate
iii) Iron(II) bromide
iv) Dinitrogen tetroxide
Describe methods to separate the following mixtures:
i) Iron fillings, sodium chloride, sand, and gold nuggets.
ii) Hexane, water and acetone.
|Relative mass||1 amu||1 amu||0.0005 amu|
|Electron Shell Diagram||Lewis Dot Diagram|
Isotopes have the same number of protons but different numbers of neutrons.
Calcium has two electrons in its outer shell; therefore, it is easier for calcium to lose two electrons to achieve a noble gas electron structure than to gain six electrons. Since calcium loses electrons to become stable, it will become a positively charged ion (i.e. cation).
Chlorine has seven electrons in its outer shell; therefore, it is easier for chlorine to gain one electron to achieve a noble gas electron structure than to lose seven electrons. Since chlorine gains an electron to become stable, it will become a negatively charged ion (i.e. anion).
Atomic radii: Going down any group in the periodic table, the atomic radius increases. This is due to the requirement of new shells to accommodate increasing number of electrons. Repulsions between shells (shielding effects from the inner electrons) expand the atomic radius. Going across any period from left to right in the periodic table, the atomic radius decreases. This is due to an increasing effective nuclear charge (more protons in the nucleus) attracting electron shells closer to the nucleus.
Electronegativity: As you move down a group, electronegativity decreases as a consequence of lower effective nuclear charge (due to increasing the number of electron shells). As you move across a period from left to right, electronegativity increases as a consequence of higher effective nuclear charge.
Metals: Hard, malleable, ductile, shiny, good conductor of electricity and heat, high boiling and melting point, solid at room temperature (except mercury).
Non-metals: Brittle, dull, poor conductor of electricity and heat, low boiling point and melting point, solid, liquid or gas at room temperature.
Semi-metals: have properties intermediate between those of typical metals and non-metals
Elements are pure substances that are made of only one type of atom (having the same atomic number). Compounds are pure substances that are made up of two or more different types of atoms that are chemically bonded in a fixed ratio
Homogeneous mixtures have a uniform composition, and do not have visible boundaries e.g. a solution of salty water. Heterogeneous mixtures have a non-uniform composition (uneven distribution) and visible boundaries can be seen, e.g. conglomerate rock.
Pure substances are made up of only one type of particle whereas mixtures consist of multiple types of particles (not chemically bonded). Hence a pure substance has a definite melting point at a particular atmospheric pressure whereas a mixture will have multiple melting points corresponding to the different components that make it up
Physical change involves rearrangement of particles without breaking chemical bonds. The matter is the same. The original matter can be recovered without a change in composition.
Chemical changes involves breaking and forming chemical bonds. The matter is altered in composition. The original matter cannot be recovered, a new substance is formed.
Metals can be pictured as a three dimensional lattice of positive ions (cations) submerged in a sea of delocalised electrons.
Ionic bond: an electrostatic attraction between oppositely charged ions, formed when a metal transfers an electron to a non-metal.
Covalent bond: bond that involves sharing of valence electrons between atoms, occurs between non-metals.
(i) Hydroxide OH–
(ii) Nitrate NO3–
(iii) Sulfate SO42-
(iv) Carbonate CO32-
(v) Phosphate PO43-
Ionic solids are not good conductors of electricity because the ions are held rigidly in place by electrostatic attraction of oppositely charged ions. However, when molten or dissolved in water, ionic compounds are good conductors of electricity because the ions are no longer held in a fixed position and are free to move, so they can carry charge.
Diamond has a higher high melting point compared to carbon tetrachloride. In order to melt diamond, strong covalent bonds holding the atoms need to be broken which require a large amount of heat energy. In order to melt carbon tetrachloride, only weak intermolecular forces need to be broken, which require less energy.
Diamond is insoluble in water whereas carbon tetrachloride is poorly soluble. Diamond has lower water solubility than carbon tetrachloride because it is more difficult to break the covalent bonds in diamond to allow water to surround it than to break the weak intermolecular forces between carbon tetrachloride molecules to allow water to dissolve it.
(i) Magnesium chloride: MgCl2
(ii) Sodium sulfate: Na2SO4
(iii) Iron(II) bromide: FeBr2
(iv) Dinitrogen tetroxide: N2O4
(v) CaF2 Calcium fluoride
(vi) CuO Copper(II) oxide
(vii) CO2 Carbon dioxide
(viii) PCl3 Phosphorous trichloride
- Use magnet to remove iron fillings. Sodium chloride, sand and gold nuggets would be left behind.
- Sieve the mixture. The gold nuggets would be trapped in the sieve and the sodium chloride and sand will fall through the sieve.
- Add water to mixture of sodium chloride and sand. The sand will not dissolve and sodium chloride will dissolve. Filter the mixture. The sand will be collected as the residue and salt solution will be collected as the filtrate.
- Evaporate the water from the filtrate to collect the sodium chloride
- Use a separating funnel to separate the hexane from the mixture of water and acetone (hexane is immiscible with water and acetone is miscible with water). Hexane is less dense and will be the top layer.
- Distil the water/acetone mixture. Acetone has a lower boiling point and will be collected first
The next part of this Year 11 Chemistry Exam series is also available: Year 11 Chemistry Exam Questions Part 2: Metals
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