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Hydrogen chloride and water are simple molecular, covalent compounds - Edexcel - GCSE Chemistry - Question 3 - 2017 - Paper 1
Question 3
Hydrogen chloride and water are simple molecular, covalent compounds. (a) The formula of a molecule of water is H₂O. Describe what this formula shows about a molecul... show full transcript
Worked Solution & Example Answer:Hydrogen chloride and water are simple molecular, covalent compounds - Edexcel - GCSE Chemistry - Question 3 - 2017 - Paper 1
Step 1
Describe what this formula shows about a molecule of water.
Answer
The formula H₂O represents a molecule of water, which consists of two hydrogen (H) atoms and one oxygen (O) atom. This indicates that:
- There are two hydrogen atoms that are covalently bonded to a single oxygen atom.
- The '2' in H₂ signifies the presence of two hydrogen atoms, which are required to form a stable water molecule.
- Oxygen, which has a high electronegativity, shares its electrons with the hydrogen atoms, leading to the formation of a polar molecule.
Thus, the formula captures the elemental composition and molecular structure of water.
Step 2
Describe what is meant by a covalent bond.
Answer
A covalent bond is a type of chemical bond that involves the sharing of electron pairs between atoms. Specifically in a molecule of water:
- Each hydrogen atom shares one of its electrons with the oxygen atom, creating a shared pair of electrons.
- This sharing allows the atoms to achieve a more stable electron configuration.
- The result is a strong bond that holds the atoms together in the molecule. Covalent bonds can occur between similar or different atoms, but they are characterized by the sharing of electrons rather than transfer, as seen in ionic bonds.
Step 3
Draw a dot and cross diagram of a molecule of hydrogen chloride, HCl.
Answer
To represent the dot and cross diagram for hydrogen chloride (HCl):
- Draw a circle around each atom, with 'H' for hydrogen and 'Cl' for chlorine.
- Place a dot (•) to represent the electron from hydrogen and a cross (×) to denote one of the seven electrons from chlorine that is involved in the bond.
- Indicate the shared pair of electrons between H and Cl, showing the connection between them.
The diagram would look like this:
[ H • ] --- [ Cl × ]
- There should be additional crosses around the chlorine atom to represent the three remaining unshared electrons.