Lithium, sodium and potassium are reactive metals in group 1 of the periodic table - Edexcel - GCSE Chemistry Combined Science - Question 3 - 2018 - Paper 1
Question 3
Lithium, sodium and potassium are reactive metals in group 1 of the periodic table.
(a) Sodium metal tarnishes in air to form a layer of sodium oxide on its surface... show full transcript
Worked Solution & Example Answer:Lithium, sodium and potassium are reactive metals in group 1 of the periodic table - Edexcel - GCSE Chemistry Combined Science - Question 3 - 2018 - Paper 1
Step 1
Sodium oxide empirical formula calculation
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Answer
Calculate the number of moles of sodium (Na) and oxygen (O).
Moles of Na:
Moles of Na=molar massmass=23g/mol0.92g=0.04mol
Moles of O:
Moles of O=16g/mol0.32g=0.02mol
Determine the empirical ratio of moles of Na to O:
The ratio:
0.02mol O0.04mol Na=2:1
Write the empirical formula of sodium oxide based on the ratio:
Empirical formula:
Na2O
Step 2
Sodium hydroxide reaction
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Answer
The reaction can be summarized by the equation:
2 Na (s)+2extH2O (l)→2NaOH (aq)+H2(g)
Step 3
Increase in reactivity from lithium to sodium to potassium
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Answer
Lithium (Li) has the electron configuration of 1s² 2s¹, sodium (Na) is 1s² 2s² 2p⁶ 3s¹, and potassium (K) is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹.
As you move down Group 1 from lithium to potassium, the outer electron is in a higher energy level.
The outer electron is further from the nucleus, leading to a reduced electrostatic attraction between the outer electron and the nucleus, making it easier for the atom to lose that electron.
Consequently, potassium is more reactive than sodium, which is more reactive than lithium.
