The diagram shows a model of a water molecule - Edexcel - GCSE Chemistry - Question 4 - 2012 - Paper 1
Question 4
The diagram shows a model of a water molecule.
hydrogen atom.
oxygen atom.
hydrogen atom.
covalent bond
(a) Explain, in terms of electrons, how a covalent bond ... show full transcript
Worked Solution & Example Answer:The diagram shows a model of a water molecule - Edexcel - GCSE Chemistry - Question 4 - 2012 - Paper 1
Step 1
Explain, in terms of electrons, how a covalent bond is formed between an oxygen atom and a hydrogen atom.
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Answer
A covalent bond is formed when an oxygen atom shares its electrons with hydrogen atoms. Oxygen has six electrons in its outer shell and requires two more to achieve a stable octet. Each hydrogen atom has one electron and needs another to fill its outer shell. When an oxygen atom shares its electrons with two hydrogen atoms, they form covalent bonds, resulting in a stable H₂O molecule.
Step 2
Calculate the relative formula mass of water, H₂O.
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Answer
To calculate the relative formula mass of water (H₂O), we add the relative atomic masses of its constituent elements:
Hydrogen (H): 2 atoms × 1.0 = 2.0
Oxygen (O): 1 atom × 16 = 16.0
Total relative formula mass = 2.0 + 16.0 = 18.0
Step 3
Write the balanced equation for this reaction.
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Answer
The balanced equation for the combustion of hydrogen in oxygen to form water is:
ightarrow 2H_2O$$
Step 4
Calculate the percentage yield.
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Suggest one reason why less than 4.0 g of water was obtained in this experiment.
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Answer
One reason for obtaining less than 4.0 g of water could be experimental error, such as loss of water during handling, evaporation, or incomplete reaction due to insufficient hydrogen or oxygen.
