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Question 1
The 'dot and cross' diagram below represents a molecule of ammonia. |
a) | What is the chemical formula of ammonia?
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b) | What type of bond is present in a molecule of ammonia?
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c) | Explain how these bonds are formed.
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Question 2
Hydrogen halides are important chemicals. The diagram below represents a molecule of hydrogen fluoride. |
a) | The diagram above is a 'dot and cross' diagram. What type of particles are represented by dots and crosses?
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b) | What type of chemical bond holds the atoms in the hydrogen fluoride molecule together? A ionic bonding B covalent bonding C metallic bonding
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c) | Predict the physical state of hydrogen fluoride at room temperature and pressure. Explain your answer.
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Question 3
Methane, CH4, is a simple molecule. |
a) | Draw a 'dot and cross' diagram to represent a molecule of methane, CH4. (You may need a periodic table)
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b) | The bonds in a methane molecule are covalent bonds. What is a covalent bond?
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c) | Which one of the statements below about the properties of small covalent molecules is correct? A they are normally solids at room temperature B they have relatively high melting and boiling points C they do not conduct electricity when dissolved in water
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Question 4
Nitrogen is an element in group 5 of the periodic table. |
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b) | How many electrons does nitrogen need to gain in order to achieve a noble gas electron configuration? A 1 B 3 C 5 D 0
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c) | The displayed formula of nitrogen gas, N2, is shown in the image below. |
c) i) | What does each single line represent in the formula above?
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c) ii) | Draw a 'dot and cross' diagram to show the bonding in a molecule of nitrogen gas.
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Question 5
Air is made up of a mixture of different gases. The principal constituents of Earth’s atmosphere are nitrogen (78%) and oxygen (21%). There are also other gases at lower concentrations. These gases include carbon dioxide, methane, as well as water vapour at varying concentrations. Draw a dot and cross bonding diagram for two of the compounds mentioned above.
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Question 6
Chlorine is an element in group 7 of the periodic table. |
a) | What common name is used for the elements of group 7?
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b) | Write the electronic structure of a chlorine atom.
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c) | Draw a dot and cross diagram to show the bonding in a molecule of chlorine, Cl2.
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d) | Chlorine is a yellow-green gas at room temperature. Explain why chlorine and other small covalent molecules are gases at room temperature.
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Question 7
Images A to E show different ways of representing a methane molecule. Describe what information can be obtained from each representation. Include the limitations of these representations in your answer.
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Question 8
Water is a compound of hydrogen and oxygen. |
a) | Give the chemical formula of water.
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b) | Write the electronic structures of a hydrogen atom and an oxygen atom.
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c) | Complete the dot and cross diagram to show the bonding in a molecule of water. Show outer shell electrons only.
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d) | Does pure water conduct electricity? Explain your answer.
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Question 9
Carbon dioxide (CO2) is a greenhouse gas. |
The image below shows the electronic configuration of an atom of carbon and an atom of oxygen. |
a) | Give the atomic numbers of carbon and oxygen.
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b) | Draw a dot and cross diagram to show the covalent bonding in a molecule of carbon dioxide, CO2. Show outer electrons only.
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c) | Explain why carbon dioxide is a gas at room temperature.
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d) | Carbon dioxide can also be represented using a displayed formula. Draw the displayed formula of carbon dioxide.
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e) | Give one advantage of the dot and cross diagram compared to the displayed formula.
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Question 10
Oxygen, O2, is a simple molecular, covalent substance. |
a) | Draw a 'dot and cross' diagram for the molecule of oxygen. (You may need a periodic table)
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b) | What is the name of the type of bond present in an oxygen molecule? A ionic bond B double covalent bond C intermolecular bond D single covalent bond
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c) | Explain the electrical conductivity of simple molecular substances such as oxygen.
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d) | Explain, in terms of structure, why oxygen is a gas, even at low temperatures.
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Question 11
The table below is missing certain pieces of data. Complete the table by filling in the blank spaces. (You may use a periodic table)
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Question 12
Glass is made from silicon dioxide. |
a) | Describe the structure and bonding in silicon dioxide.
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b) | Silicon dioxide has a very high melting point. Other substances are added to silicon dioxide to make glass. Glass melts at a lower temperature than pure silicon dioxide. Suggest why.
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