Fig. 1 shows a dot-and-cross diagram for a molecule of ammonia, NH3. A refrigeration company uses ammonia in a sealed system because it can evaporate and co...
Question 1 Report
Fig. 1 shows a dot-and-cross diagram for a molecule of ammonia, NH3. A refrigeration company uses ammonia in a sealed system because it can evaporate and condense at suitable temperatures. The technician must understand that ammonia is a molecular compound, not an ionic compound. Nitrogen has five electrons in its outer shell and each hydrogen atom has one. The diagram includes one pair of electrons that is not shared in a bond.
(a) Name the type of bond between nitrogen and hydrogen. [1]
(b) Complete the sentence: the electrons in each bond are ______ between atoms. [1]
(c) Explain why liquid ammonia does not conduct electricity. [2]
The diagram shows a carbon nanotube used in the frame of a lightweight drone. It is a rolled sheet of carbon atoms joined by covalent bonds. The manufacturer selects nanotubes because a small mass of material can make a strong structure. The same material can conduct electricity, which is useful for a sensor cable. A student suggests that the tube must be made of simple molecules because it contains only carbon.
(a) Name the type of structure in a carbon nanotube. [1]
(b) Explain why the nanotube is strong. [2]
(c) What particles allow the nanotube to conduct electricity? [1]
(d) Describe why the student's suggestion is incorrect. [1]
Answer Details
Ammonia
(a) The bond between nitrogen and hydrogen is a covalent bond. [1]
(b) The electrons in each covalent bond are shared between atoms. [1]
(c) Liquid ammonia does not conduct because it has no mobile ions and no delocalised electrons to carry electrical charge. [2]
Carbon nanotube
(a) A carbon nanotube has a giant covalent structure. [1]
(b) Strong covalent bonds join the carbon atoms. These bonds extend through the tube as a continuous network, so a large force is needed to break the structure. [2]
(c) The particles that allow conduction are delocalised electrons. [1]
(d) The suggestion is incorrect because a nanotube is a continuous giant network, not separate simple molecules. [1]
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