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Covalent substances can be simple molecular covalent or giant covalent - Edexcel - GCSE Chemistry Combined Science - Question 5 - 2018 - Paper 1
Question 5
Covalent substances can be simple molecular covalent or giant covalent. (i) Ammonia is a simple molecular, covalent substance. Which is the most likely set of prope... show full transcript
Worked Solution & Example Answer:Covalent substances can be simple molecular covalent or giant covalent - Edexcel - GCSE Chemistry Combined Science - Question 5 - 2018 - Paper 1
Step 1
Which is the most likely set of properties for ammonia?
Answer
Ammonia (NH₃) is a simple molecular substance characterized by low melting and boiling points, and it does not conduct electricity in its liquid state. The most likely properties, therefore, can be found in option B:
- Melting point: -78 °C
- Boiling point: -33 °C
- Ability to conduct: does not conduct.
Step 2
Ammonia, NH₃, is made by reacting nitrogen with hydrogen. Write the balanced equation for this reaction.
Answer
The balanced equation for the formation of ammonia from nitrogen and hydrogen is:
ightarrow 2NH_3$$ This equation shows one nitrogen molecule combining with three hydrogen molecules to form two ammonia molecules.Step 3
Draw a dot and cross diagram for the molecule of oxygen.
Answer
In the dot and cross diagram for the oxygen molecule (O₂), each oxygen atom shares two electrons, forming a double bond. Here’s how the diagram looks:
O O
•• ••
•• ••
Each dot represents an electron from one oxygen atom, and each cross represents an electron from the other oxygen atom.